Citrus Genetic Resources in California

Transcription

Citrus Genetic Resources
in California
Analysis and Recommendations
for Long-Term Conservation
Report of the Citrus Genetic Resources Assessment Task Force
T.L. Kahn, R.R. Krueger, D.J. Gumpf, M.L. Roose, M.L. Arpaia, T. A. Batkin, J.A. Bash,
O.J. Bier, M.T. Clegg, S.T. Cockerham, C.W. Coggins Jr., D. Durling, G. Elliott,
P. A . Mauk, P.E . McGuire, C. Orman, C.O. Qualset, P. A. Roberts, R.K. Soost,
J. Turco, S.G. Van Gundy, and B. Zuckerman
Report No. 22 June 2001
Published by
Genetic Resources Conservation Program
Division of Agriculture and Natural Resources
UNIVERSITY OF CALIFORNIA
i
This report is one of a series published by the University of California Genetic Resources Conservation Program (technical editor: P.E. McGuire) as part of the public
information function of the Program. The Program sponsors projects in the collection, inventory, maintenance, preservation, and utilization of genetic resources
important for the State of California as well as research and education in conservation biology. Further information about the Program may be obtained from:
University of California
One Shields Avenue
Davis, CA 95616 USA
(530) 754-8501
FAX (530) 754-8505
e-mail: [email protected]
Website: http://www.grcp.ucdavis.edu/
Additional copies of this report may be ordered from this address.
Citation: Kahn TL, RR Krueger, DJ Gumpf, ML Roose, ML Arpaia, TA Batkin, JA Bash, OJ Bier,
MT Clegg, ST Cockerham, CW Coggins Jr, D Durling, G Elliott, PA Mauk, PE McGuire, C Orman,
CO Qualset, PA Roberts, RK Soost, J Turco, SG Van Gundy, and B Zuckerman. 2001. Citrus genetic
resources in California: Analysis and recommendations for long-term conservation. Report No. 22.
University of California Division of Agriculture and Natural Resources, Genetic Resources Conservation Program, Davis CA USA.
© 2001 Regents of the University of California
Cover photograph: Assemblage of citrus fruits. Photo credit: Eric Sander, 10558 Putney Rd, Los Angeles, CA 90064,
http://www.ericsander.com, used by permission.
Inside front cover: Top row, from left: Washington navel orange (CRC #1241) and Delta Valencia (Delta seedless) orange (CRC #3963); Second row, from left: Vainiglia pink-fleshed sweet orange (CRC #3801) and Moro blood orange
(CRC #3830); Third row, from left: Mexican lime (CRC #1710), Variegated pink-fleshed Eureka lemon (CRC #2367),
and Citrus hystrix (CRC #2454); Bottom row, from left: Frost Nucellar #1 (Owari) Satsuma mandarin orange (CRC
#3178) and Gold Nugget mandarin orange (CRC #3913) Photo credit: All individual photographs by Ottillia J. Bier.
Inside back cover: Sliced fruits demonstrating diversity in the Citrus Variety Collection. Photo credit: William S.
Myerchin
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disability, medical condition (cancer-related or genetic characteristic), ancestry, marital status, age, sexual orientation, citizenship, or status as a covered veteran
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Natural Resources, 1111 Franklin St., 6th Floor, Oakland CA 94607-5200. Tel. (510) 987-0096.
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TABLE OF CONTENTS
Preface ................................................................... v
3. Citrus genetic resources in California ................. 15
Citrus Genetic Resources Assessment
Task Force membership ......................................... vii
• Citrus Variety Collection (CVC) ............................ 15
Charge to Task Force ............................................. ix
• Citrus Clonal Protection
Program (CCPP) ..................................................... 17
• Citrus Evaluation Blocks (CEBs) ............................ 16
Abbreviations and acronyms used in
this report .............................................................. x
• National Clonal Germplasm Repository
for Citrus and Dates (NCGRCD) .......................... 18
Executive summary .............................................. xiii
• Interrelationships among CVC,
CEBs, CCPP, and NCGRCD .................................. 19
1. Introduction ....................................................... 1
4. US citrus genetic resources outside
California ........................................................... 23
2. Background ........................................................ 3
• History of citrus in California .................................... 3
• Economic value of citrus to California ...................... 4
5. International citrus genetic resources ................. 25
• Taxonomy of citrus .................................................... 5
• Biology of citrus ......................................................... 5
6. Analysis and recommendations in support
of citrus genetic resources in California ............... 29
• Origin and distribution of citrus ................................ 6
Literature cited ...................................................... 37
• Domestication of citrus .............................................. 6
Appendix. Holdings of the University of California,
Riverside Citrus Variety Collection (CVC) ............ 43
• Genetic diversity of citrus .......................................... 6
• Utilization of genetic resources
in California ............................................................... 8
• Importance of citrus genetic
resources conservation ............................................. 11
• Acquisition of citrus genetic
resources ................................................................... 12
• Conservation of citrus
genetic resources ...................................................... 14
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LIST OF TABLES AND FIGURES
Figure 7. Fruit and branch of Australian finger lime
(Microcitrus australasica CRC #1484). ............................ 8
Tables
Executive summary table 1. Costs of personnel,
equipment, supplies, and facility requirements
for the CVC. ................................................................. xii
Figure 8. Example of diversity at the molecular level. .. 9
Figure 9. Howard B. Frost (l.), first citrus breeder
at UC Riverside (beginning in 1914) and Robert K.
Soost, who succeeded Frost as citrus breeder in 1949
and was a curator of the CVC from 1982 until 1986. ... 9
Table 1. Summary of taxa in subgenus Citrus. ............... 6
Table 2. Chronology of UCR Citrus Variety
Collection supervision. ................................................. 15
Figure 10. Fruit and branch of Gold Nugget
mandarin orange (CRC #3913). .................................. 10
Table 3. Type and number of accessions in the CVC. 17
Table 4. Research projects utilizing accessions
in the CVC (1997–2001). ............................................ 32
Figure 11. Trunk of root-stock showing damage
from Phytophthora infection. ......................................... 10
Table 5. Costs of personnel, equipment, supplies,
and facility requirements for the CVC. ....................... 35
Figure 12. Trunk with bark removed to reveal
damage caused by the citrus tristeza virus (CTV). ...... 11
Figure 13. Successful graft. .......................................... 11
Figures
Figure 14. An incompatible graft shown with
bark stripped away. ....................................................... 11
Executive summary figure 1. Movement of
citrus genetic resources into, within, and out of
the California system for conservation and
utilization of citrus genetic resources. .......................... xv
Figure 15. Hiryu (Flying Dragon trifoliate orange,
Poncirus trifoliata, CRC #3795). ................................... 12
Figure 16. W.P. Bitters, curator of the Citrus
Variety Collection from 1946 to 1982. ........................ 16
Figure 1. December 23, 1914 headlines from
the Riverside Daily Press. ............................................... 4
Figure 17. Budwood source trees for the Citrus
Clonal Protection Program in a screenhouseprotected planting at the Lindcove Research
and Extension Center. .................................................. 18
Figure 2. Original Citrus Experiment Station
staff on the steps of the main office-laboratory
building ca. 1916. ........................................................... 4
Figure 18. Seedlings of indicator plants for
indexing, growing in cool-temperature chamber
of NCGRCD greenhouse facilities. .............................. 19
Figure 3. A cultivation demonstration at
Riverside ca. 1917. ......................................................... 5
Figure 4. Microscopic cross-section of developing
seed revealing the multiple nucellar embryos
contained within (polyembryony). ................................ 7
Figure 19. Movement of citrus genetic resources
into, within, and out of the California system
for conservation and utilization of citrus genetic
resources. ...................................................................... 20
Figure 5. Germinating seeds revealing the
multiple nucellar seedlings emerging from the
seed at the left (polyembryony). .................................... 7
Figure 20. Headstand of furrow irrigation system. ...... 31
Figure 21. The squashed, softened stigma,
one day after pollination, reveals germinating
viable pollen grains. ...................................................... 34
Figure 6. The strikingly distinct fruits of Buddha’s
hand citron (Fingered citron, Citrus medica,
CRC #3768). .................................................................. 8
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PREFACE
CITRUS CROPS IN CALIFORNIA mean primarily navel
and valencia oranges, lemons, grapefruit, and tangerines,
tangelos, and tangors. By the most recent figures available (1998–1999) at the time of this writing, the California Agricultural Statistics Service reports the following
total values for these crops: navel oranges $227 million;
valencia oranges $188 million; lemons $214 million;
grapefruit $81 million; and tangerines et al. $23 million.
Altogether that’s about a three-quarter-billion-dollar
citrus industry, placing citrus in the top ten of California
crops. Three of these—oranges, lemons, and grapefruit—
are individually also among the top 30 California export
crops. To sustain this productivity and competitiveness
in the US by creating new varieties, maintaining the
diversity of citrus crops, ensuring healthy trees in the
field, and desirable fruit in the marketplace, it is imperative that breeders, researchers, and the industry have
access to reliable collections of citrus genetic resources.
As this report shows, this has been possible by virtue of
an unofficial state ‘system’ for conserving and utilizing
citrus genetic resources. This system is comprised of University of California, state, and federal organizations and
their interrelationships are documented herein.
The reliance on ex situ collections of genetic diversity for crop improvement is typical for most California
crops. Of the 350 agricultural commodities produced in
California, less than 10 percent are either species indigenous to California or related to California indigenous
species. The vast majority are introduced from outside
California and usually from outside the US as well. This
puts a premium on the existing ex situ collections maintained in California. Generating a collection from the
areas of a given crop’s genetic diversity is increasingly
difficult, if not impossible, for most crops.
As effective as it has been, the current situation for
citrus is a decentralized system that has been driven by
need and opportunity, not by careful planning involving
all components. While this report has focused primarily
on the University of California component—the Citrus
Variety Collection (CVC) at the UC Riverside campus,
the task force undertaking this analysis was comprised of
representatives from all components. The role of citrus
in California’s economy and the history of citrus in
southern California were driving forces for the establishment of the University of California Citrus Experiment
Station in 1906, and ultimately the UC Riverside campus, now a major university in its own right. However,
there were concerns that the current and long-term financial and facility status of the CVC was not adequate
to allow it to continue as the primary collection of citrus
genetic resources for California. No organization is in
the position to single-handedly resolve this situation.
The UC Genetic Resources Conservation Program, with
its mission of facilitating genetic resources collections for
species important to California, and the UC Riverside
College of Natural and Agricultural Sciences together
convened this task force as a first step in addressing this
concern for the CVC. The major objective of this task
force was to obtain a clear statement of the value of the
collection, the role it plays, and the resources necessary
to sustain and enhance it. With the findings of this report as motivation and its recommendations as a strategy, we hope the targeted organizations will find it imperative to contribute to the solution of this crisis in support of citrus genetic resources for the good of California
citrus production and citrus research in general.
Calvin O. Qualset, Director
Division of Agriculture and Natural Resources
Michael T. Clegg, Professor
Dept. of Botany & Plant Sciences
Former Dean (1994–2000)
College of Natural and Agricultural Sciences
University of California, Riverside
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CITRUS GENETIC RESOURCES ASSESSMENT TASK FORCE
MEMBERSHIP
Mary Lu Arpaia, Cooperative Extension Subtropical Horticulturist, Dept. of Botany and Plant
Sciences, University of California, Riverside CA
Robert R. Krueger, Curator, USDA-ARS National
Clonal Germplasm Repository for Citrus and
Dates, Riverside CA
Ted A. Batkin, President, Citrus Research Board,
Visalia CA
Patrick E. McGuire, Associate Director, Genetic
Resources Conservation Program, Div. of Agriculture and Natural Resources, University of
California, Davis CA
John A. Bash, Staff Research Associate, Citrus
Clonal Protection Program, Dept. of Plant Pathology, University of California, Riverside CA
Peggy A. Mauk, Cooperative Extension Subtropical Horticultural Advisor, Riverside and San
Bernardino Counties, University of California
Ottillia J. Bier, Staff Research Associate, Citrus
Variety Collection, Dept. of Botany and Plant
Sciences, University of California, Riverside CA
Chuck Orman, Director of Science and Technology, Sunkist Growers, Ontario CA
Michael T. Clegg, ex officio, Professor of Genetics, Dept. of Botany and Plant Sciences and
Former Dean (1994–2000), College of Natural
and Agricultural Sciences, University of California, Riverside CA
Calvin O. Qualset, ex officio, Director, Genetic
Resources Conservation Program, Div. of Agriculture and Natural Resources, University of
California, Davis CA
Stephen T. Cockerham, Superintendent, Agricultural Operations, University of California, Riverside CA
Philip A. Roberts, Associate Dean, Agricultural
Experiment Station and Cooperative Extension,
College of Natural and Agricultural Sciences
and Professor of Nematology, Dept. of Nematology, University of California, Riverside CA
Charles W. Coggins Jr., Professor Emeritus of
Plant Physiology, Dept. of Botany and Plant Sciences, University of California, Riverside CA
Mikeal L. Roose, Professor of Genetics, Dept. of
Botany and Plant Sciences, University of California, Riverside CA
Don Durling, Durling Nursery, Inc., Fallbrook CA
Georgia Elliott, Executive Director of Corporate
and Foundation Relations, Development Office, University of California, Riverside CA
Robert K. Soost, Professor Emeritus of Genetics,
Dept. of Botany and Plant Sciences, University
of California, Riverside CA
David J. Gumpf, Director, Citrus Clonal Protection Program and Professor, Dept. of Plant Pathology, University of California, Riverside CA
John Turco, Corotto/Turco Farms, San Jose CA
Seymour D. Van Gundy, Professor Emeritus of
Nematology, Dept. of Nematology, University
of California, Riverside CA
Tracy L. Kahn, Task Force chair, Curator, Citrus
Variety Collection; Senior Museum Scientist,
Dept. of Botany and Plant Sciences; and Lecturer, Dept. of Biology, University of California,
Riverside CA
Bob Zuckerman, B&Z Nursery Inc., Porterville CA
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CHARGE TO THE TASK FORCE
EVALUATE THE CURRENT STATUS of the Citrus Variety
Collection (CVC) at the University of California, Riverside campus with regard to its contents, utilization, and
value and its interrelationships with other California,
federal, and international citrus genetic resources and
research organizations and activities. Prepare a report
documenting these findings and include recommendations for organizational, fiscal, and administrative steps
necessary to ensure the long-term security of the CVC as
a dynamic genetic resources conservation facility serving
the California citrus industry and University of California research, teaching, and extension objectives.
ix
ABBREVIATIONS AND ACRONYMS USED IN THIS REPORT
APHIS
Animal and Plant Health Inspection Service of the US Dept. of Agriculture
IOCV
International Organization of Citrus Virologists
ARS
Agricultural Research Service of the US
Dept. of Agriculture
IPGRI
International Plant Genetic Resources Institute
CCPP
Citrus Clonal Protection Program
LREC
CDFA
California Department of Food and Agriculture
UC Lindcove Research and Extension
Center
NCGRCD
National Clonal Germplasm Repository for
Citrus and Dates
NPGS
National Plant Germplasm System
PI
Plant Introduction, USDA NPGS
CEB
Citrus Evaluation Block
CNAS
College of Natural and Agricultural Sciences, University of California, Riverside
CRB
Citrus Research Board
RAPD
random amplified polymorphic DNA
CRC-AES
Citrus Research Center and Agricultural
Experiment Station
RFLP
restriction fragment length polymorphism
SCREC
CSIRO
Commonwealth Scientific and Industrial
Research Organization
UC South Coast Research and Extensions
Center
TAMUK
Texas A&M University, Kingsville
CTV
citrus tristeza virus
UC
CVARS
UCR Coachella Valley Agricultural Research Station
UCR
University of California, Riverside
CVC
Citrus Variety Collection
USDA
United States Department of Agriculture
CVIP
Citrus Variety Improvement Program
USHRL
United States Horticultural Research Laboratory, USDA
ELISA
enzyme-linked immuno-sorbant assay
VI
Variety Introduction
FAO
Food and Agriculture Organization of the
United Nations
WFFVC
A.H. Whitmore Foundation Farm Variety
Collection
GCGN
Global Citrus Germplasm Network
GRIN
Genetic Resources Information Network, a
unit of the National Genetic Resources
Program
x
EXECUTIVE SUMMARY
Because of the integration of the CVC with the CCPP
and NCGRCD, there are no major impediments to importation of citrus genetic resources into California.
FINDINGS
The California citrus genetic resources
conservation and utilization system
Citrus genetic resources are not native to California,
meaning that ex situ conservation in California of acquired accessions is the only way to ensure their availability for continued use. In addition, access to citrus
genetic resources from native habitats is increasingly undependable, putting a premium on conservation of what
has already been collected.
CITRUS CROPS (especially oranges, lemons, and grapefruit) are a significant component of California’s agricultural production. To maintain or increase their value,
commercial citrus varieties must be available to meet the
needs of the diverse citrus producing regions in California and consumer preferences. Ensuring continued variety development, healthy trees in the field, and desirable
fruit in the marketplace means continued research, breeding, and product development. All of this requires reliable availability in California of citrus genetic resources.
Expanded use of molecular techniques such as markerassisted selection and transformation in breeding programs will increase the value of genetic resources for
crop improvement and allow the use of more distantly
related species as gene sources for cultivated species.
This means that increasingly the concept of genetic resources will expand to include cDNA and genomic
DNA libraries, and the probes, clones, and sequences
derived from them.
California maintains one of the largest and most diverse
assemblages of citrus genetic resources in the world with
a functional conservation and utilization system comprising three primary units: the Citrus Variety Collection
(CVC) and the Citrus Clonal Protection Program
(CCPP) at the University of California, Riverside and
the USDA National Clonal Germplasm Repository for
Citrus and Dates (NCGRCD). Closely collaborating
with these three units are the UC Riverside Citrus
Breeding Program and the California Citrus Research
Board.
The Citrus Variety Collection
✦ The CVC, with 865 accessions, is the key component
of the California system for maintaining citrus genetic
resources.
✦ The CVC is the oldest component, initiated in 1910
with a focus on establishing a broad representation of
accessions from all citrus-growing regions of the
world.
This California citrus genetic resources system is unique
among organized collections throughout the world and
serves as a model for conservation, utilization, and
teaching. The system maintains a broad cross-section of
genetic diversity along with complementary programs
that provide virus-free budwood for commercial use, programs for distributing genetic resources for research uses,
and research programs for crop improvement, physiology,
biochemistry, phylogeny, genetics, and molecular biology. Executive summary figure 1 illustrates the flow of
genetic resources into and out of the system and among
these units, the Citrus Evaluation Blocks (CEBs), and
the UC Riverside Citrus Breeding Program.
✦ The collection presents a long-standing investment of
human resource efforts and considerable investment
of public funds through the University of California,
State of California, US Dept. of Agriculture as well as
funds and donations of plant materials from private
and commercial resources. Clearly, this genetic resources collection could not be developed if it were to
be initiated today.
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Citrus clonal
material from
outside California
and the US
Citrus seed and pollen
from outside California
and the US
Imported into California directly to
the CCPP under US federal and
California regulations
Imported into California directly to the
CVC or the NCGRCD under US federal
and California regulations.
Citrus Clonal
Protection Program
(CCPP)
UC Riverside
Citrus Breeding
Program
Movement of citrus
genetic resources
within California
Citrus
Evaluation
Blocks (CEBs)
National Clonal Germplasm
Repository for Citrus and
Dates (NCGRCD)
Citrus Variety
Collection
(CVC)
Citrus genetic resources move to California citrus nurseries as virus-free budwood from the CCPP and
to national and international citrus researchers as virus-free budwood from the NCGRCD and as
seed and pollen from the CVC and NCGRCD.
Commercial citrus
nurseries
California
citrus growers
National and
international citrus
researchers
Consumers
Movement of citrus genetic resources into, within, and out of the Californa system
for conservation and utilization of citrus genetic resources.
Executive summary figure 1.
xii
✦ The security of CVC accessions and the extent of its
activities to enhance the scope and value of the accessions are impaired by the piece-meal, transient,
and undependable nature of its current funding. Only
partial support for the curator position is secure on a
reasonably long-term basis.
USDA financial support to the operations of the
CVC has been provided in the past two years through
a short-term cooperative agreement.
✦ Integrated pest management techniques are not optimally employed in the management of CVC
plantings.
✦ The full range of tasks necessary for curating and administering the CVC require at a minimum a fulltime curator, a full-time technical assistant, and seasonal part-time employees. These tasks cannot be met
with the current levels of support without impairing
the integrity of the collection for current and future
uses.
✦ The current rootstock status of the CVC collection
appears to be adequate with respect to resistance to
known disease threats.
✦ Information on the accessions of the CVC has been
maintained on a computer database since 1996, replacing a handwritten index card system initiated at
the inception of the CVC.
✦ Increasing requests for educational outreach programs
from the CVC is a sign of public interest in genetic
resources, especially citrus. Meeting these requests
limits the time that can be devoted to critical aspects
of maintenance and evaluation of the accessions in
the CVC. There is no funding dedicated to these activities.
✦ Electronic access to some information about the CVC
is at the CVC website (http://cnas.ucr.edu/~citrus/
index.htm). In addition, some information about the
CVC collection is available from the USDA GRIN
database (http://www.ars-grin.gov/).
✦ Greenhouse facilities are inadequate for the CVC to
carry out propagation and maintenance of accessions.
✦ Immediate facility and equipment needs appear to be
met through availability of space through the UCR
Dept. of Botany and Plant Sciences and loans of some
specialized equipment. However, there is no longterm commitment to these space arrangements and
no plans to accommodate CVC growth.
RECOMMENDATIONS
The California citrus genetic resources
conservation and utilization system
✦ Normal care of a citrus genetic resources collection is
considerably more complex and expensive than the
maintenance of plants in a commercial grove. CVC
currently receives horticultural management services
from the UC Riverside Agricultural Operations department. However, the trend is for reduction of services that can be provided and this impacts the longterm security of the CVC. It may be necessary for the
CVC budget to accommodate these management
costs.
1. No changes in the management structure of the
CVC, the CCPP, or the NCGRCD are advocated. The
continued close collaboration among the three units is
essential to the functioning of a citrus genetic resources
conservation and utilization system for California.
2. The establishment of a California Citrus Genetic
Resources Advisory Committee (CACGRAC) is recommended. This committee, composed of research and
extension workers, agency and University administrators, growers, processors, marketers, consumers, and others, will provide guidance to the staffs of the units that
comprise the California citrus genetic resources conservation and utilization system to assure the acquisition of
critical genetic resources and their long-term conservation and efficient distribution.
✦ Few granting agencies will fund baseline genetic resources conservation activities. Some successful proposals by the curator have furnished indirect support
for the CVC. However, short-term (annual) grants
cannot be a successful long-term strategy for conservation activities.
✦ The value of the CVC to the US National Plant
Germplasm System, operated by the US Dept. of Agriculture, is reflected by several points: (1) seed and
pollen requests to the NCGRCD are filled from material maintained by the CVC, (2) the CVC provides
field evaluation opportunities and vegetative material
for the NCGRCD, and (3) about 70% of the citrus
accessions listed publicly as available in the NPGS
are available only at the CVC. Some temporary
3. The dependence of the NCGRCD on the CVC for
seed and field evaluation facilities should be officially
recognized by the parent organization of each unit and
enhanced by a long-term commitment of support for the
CVC by the USDA NPGS.
4. Citrus genetic resource management for California
should expand to include resources such as DNA librarxiii
ies, probes, and clones. The appropriate unit and adequate funding for the effort should be topics for consideration by the proposed California Citrus Genetic Resources Advisory Committee. (Rec. 2 above).
Activities: Dissemination of information.
12. The CVC website is a potentially valuable distribution point for CVC collection characterization and
evaluation data. It may need relocation from its current
status on the UCR College of Natural and Agricultural
Sciences server. The website should include contact information for the staff.
The Citrus Variety Collection
Activities: Acquisition
5. There should be continued and enhanced linkages
with other national and international citrus genetic resources collections.
Personnel
13. Positions and staffing levels needed are a full-time
curator, full-time technical assistant/assistant curator,
part-time seasonal assistants, and a part-time database/
website specialist.
6. Acquisition of new accessions, both from within and
outside California and of wild or naturally occurring citrus relatives from their native habitats, is an important
function for the CVC. Acquisitions should be guided by
a plan developed with assistance of the recommended
advisory committee. Every effort should be made to acquire accessions for the CVC that are not currently
available in California, taking full advantage of the California system that allows importation of citrus genetic
resources.
Facilities and equipment
14. The CVC should have at least two up-to-date, networked computers and at least one laser-quality printer,
devoted to such activities as accessioning, data analysis
and exchange, equipment and budget monitoring, and
preparation of outreach materials.
Activities: Documentation and database management
15. Facilities and equipment needs include research
equipment, a vehicle, and a greenhouse/headhouse structure on or near the orchard site to facilitate propagation
of new or replacement accessions and field evaluation
activities, house equipment and tools, and offer a reception point for CVC visitors and tours.
7. The CVC database should be enhanced to include
digital representations of important accession characteristics such as photographs of flower, leaf, and fruit morphology, gels of biochemical and molecular genetic analyses, and disease susceptibility or resistance symptoms.
Financial resources
8. There should be continued exchange of information
between the CVC and the USDA NPGS GRIN databases.
16. The CVC needs an annual budget for operating expenses and outreach that reflects the full costs of these
activities including maintenance on facilities and equipment and depreciation on equipment (Executive summary table 1).
Activities: Maintenance
9. Full implementation of integrated pest management
techniques should be deployed in the CVC plantings
which, along with the full installation of the low-volume
irrigation system, would not only increase the efficiency
of tree cultivation in the CVC, but would also enhance
the unit as a showcase for California citrus.
17. The CVC needs funding for first-time and one-time
expenses to bring its physical facilities to a level adequate to meet its needs as a California repository of citrus genetic resources (Executive summary table 1).
18. Funding to enhance and sustain the CVC’s role in
conservation and utilization of citrus genetic resources
for California properly involves the US Government,
the State of California, the University of California, and
the citrus industry.
10. The CVC needs to monitor information about citrus
pathogens and keep in contact with citrus specialists to
anticipate disease threats to the collection.
Activities: Evaluation, characterization,
and research
19. An endowment fund should be established with interest earned being dedicated to meet annual operations
costs of the CVC. The fund should be organized under
the auspices of the UC Riverside campus with contributions from the diverse enterprises comprising the California citrus industry and individual donors. A committee
11. Users of the CVC should be encouraged to contribute to the maintenance of its collections.
xiv
composed of representatives of USDA NPGS, UC,
CDFA, and CRB and individuals having strong interest
in the preservation of citrus varieties and diversity
should be convened to develop this fund.
Administration
20. The relationship of the management of the CEBs to
management of the CVC should be formalized and the
extent of the effort required by the CVC curator to manage the CEBs needs to be defined to ensure that these
activities do not come at the expense of CVC activities.
Executive summary table 1.
Costs of personnel, equipment, and facility
requirements for the CVC.
Category
Initial and replacement
cost (dollars)
Annual cost (dollars)
Personnel
Curator (1.0 FTE)
65,000a,b
Technical Assistant (1.0 FTE)
40,000a,b
Database/website specialist (0.5 FTE)
21,000a,c
Temporary assistance
10,000a,d
Supplies
Nursery and lab supplies
5,000
25,000e
Acquisition, research, & evaluation
Equipment
Vehicle: minivan
20,000
Vertical illuminator and filter sets (Zeiss)
5,000
Computers (2)
5,000
Printer
600
Electric cart
5,000
Services received
Annual tree maintenancef
24,000
Annual tree pruning
2,000
Annual fruit reduction
7,000
Annual vehicle maintenance
2,000
Facility
Greenhouse (36’x60')/headhouse (20’x36')
200,000
Utilities for field facilities
Subtotal
2,000
235,600
203,000
235,600
227,360
Contingency fund reserve
12% of annual budget
Total
24,360
a
d
b
e
includes benefits;
estimate, actual amount will depend on job title;
c
based on Computer Resource Specialist II title,
entry level;
Work-study and summer students;
Reserved for supplies, travel, and staffing
f
Performed currently by UCR Agricultural
Operations, does not include pruning.
xv
xvi
➊
INTRODUCTION
CITRUS IS THE MOST IMPORTANT subtropical fruit crop
in North America. In California, citrus has been produced commercially since the mid-1800s. Currently approximately 275,000 acres in California are devoted to
citrus, yielding about 4.5 billion pounds of fruit annually.
In 1999, the gross on-farm value of California citrus was
about $734 million. In 1997, the export value for California citrus was approximately $454 million. Collectively, citrus is one of the top ten crops in the state. To
create new varieties, maintain a large diversity of commercial citrus varieties, and ensure healthy trees in the
field and desirable fruit in the marketplace, reliable
sources of citrus genetic resources are required. In addition, reliable collections of citrus genetic diversity are
crucial for the development of new compounds for human use, especially since wild citrus populations are rare
and habitat destruction threatens those that still exist.
One of the largest and most diverse assemblages of citrus
genetic resources in the world is maintained in California by what is, in essence, a conservation and utilization
system comprising three primary units: the Citrus Variety Collection (CVC) and the Citrus Clonal Protection
Program (CCPP) at the University of California and the
USDA National Clonal Germplasm Repository for Citrus and Dates (NCGRCD). Closely collaborating with
these three units are the UC Riverside Citrus Breeding
Program and the California Citrus Research Board.
The UC CVC is one of the most extensive collections of citrus diversity in the world, encompassing approximately 1,720 trees representing 865 accessions of
citrus and citrus relatives. This diversity is manifested
visually by types with fruits of unusual shapes, sizes, colors, and flavors growing on trees of varying heights,
forms, and foliage characteristics. In addition, in this
material there is great variation in the chemical compounds of the rind and flesh manifested by variation in
flavor, texture, and aroma. Underlying this visible and
tangible diversity is genetic diversity which can be manipulated, combined, and transferred for improvement of
citrus crops for productivity, flavor, and disease and environmental tolerance and for development of new food
and horticultural crops.
The primary users of the CVC are research scientists, plant breeders, nurserymen, growers, and citrus industry representatives. This collection was established in
1910 to provide genetic resources for citrus research in
California. In recognition of the perpetual need for genetic resources, the USDA National Plant Germplasm
System (NPGS) established the NCGRCD at UC Riverside in 1987 adjacent to the CVC. The CVC also provides genetic resources for the UC CCPP which currently provides the California citrus industry and researchers with a clean primary vegetative propagation
tissue (budwood) source of important citrus scion and
rootstock varieties.
This report reviews and summarizes the roles and
interrelationships of the programs in California (CVC,
CCPP, and NCGRCD) to recommend continued acquisition, conservation, and availability of citrus genetic
materials for California.
1
2
➋
BACKGROUND
they established in Pomona in 1890 devoted only two
acres to citrus and contained only 28 varieties.
Faced with insufficient citrus research at the
Pomona station, citrus growers in Riverside founded the
Riverside Horticultural Club to conduct cooperative research (REED 1895). In addition, they lobbied the
USDA to send citrus researchers to Riverside. In 1904,
USDA pomologist G. Harold Powell arrived to study
fruit decay (SHAMEL 1921). In 1905, the California Legislature appointed three commissioners to represent the
Regents of the University of California in selecting a
citrus experimentation site (STATUTES OF CALIFORNIA
1905). Riverside was selected, the Citrus Experiment
Station was established in 1906, and the station at Pomona was closed. The original site for the station, called
the Rubidoux Laboratory, was 23 acres on the eastern
slope of Mount Rubidoux near downtown Riverside. A
collection of citrus species and varieties was initiated at
this location in 1910.
In 1912, Herbert John Webber, a former USDA
researcher, was appointed director of the Citrus Experiment Station. Charged with selecting a site for an expanded Citrus Experiment Station, Webber inspected
many locations in California, but favored keeping the
station at Riverside. Many communities in southern
California competed for the station, but ultimately a new
475-acre site at Riverside was selected (UNIVERSITY OF
CALIFORNIA REGENTS 1914, Figure 1). Webber assembled what became known as the ‘original staff’ of the
experiment station, many of whom are regarded today as
pioneers in their field (LAWTON and WEATHERS 1989,
Figure 2). In June 1917, various experimental plots were
established at the new site (Figure 3), including 65 acres
of oranges for studies in cultivation and fertilization and
a five-acre collection containing 500 types of citrus from
all over the world. Types from the original Rubidoux
Laboratory collection (WEBBER 1918, METCALF 1963)
were included.
By its many contributions, the Citrus Experiment
Station established an international reputation for citrus
research. By act of the Regents of the University of California, the Riverside campus was declared a general campus in 1959 and graduate and professional programs were
added in 1960. In 1961, the Regents changed the name
HISTORY OF CITRUS IN CALIFORNIA
THE FIRST CITRUS TREES IN CALIFORNIA are believed to
have been planted from seed in 1769 with the founding
of the Mission San Diego de Acalá. With the establishment of additional missions, plantings of citrus trees in
mission gardens extended the presence of citrus throughout southern California (WEBBER et al. 1967). During
these early years, there were no commercial plantings of
citrus in California. In fact, it was reported that the mission padres refused to allow citrus to be planted outside
the mission orchards (LUGO 1950).
However, with the secularization of the missions in
1833, citrus became more available and small groves
were established outside the missions. In 1841, William
Wolfskill planted the first commercial orchard in Los
Angeles (EVANS 1874, DOWNEY 1874, WILSON 1965).
With the ceding of California to the United States in
1848 and the gold rush of 1849, the population of California increased dramatically, and with it, the demand
for fruit. By 1867, the USDA reported 15,000 orange
trees and 2,300 lemon trees in the Los Angeles area. In
1873, the first Washington navel orange trees were
planted at Riverside where a thriving citrus industry developed. Riverside groves contained more than 200,000
citrus trees by 1882 (ROE 1932). Inspired by the success
of citrus growers in Riverside, early California settlers
extended commercial citrus plantings to other suitable
regions of the state (LAWTON and WEATHERS 1989).
During these early years, individual citrus growers
conducted their own research on cultural and pest problems. However, with the rapid expansion of the citrus
industry came the need for more extensive agricultural
research. In 1868, the University of California was established as a land grant institution under the provisions of
the Morrill Act of 1862 (FERRIER 1930). In 1874, the
UC Agricultural Experiment Station was founded with
Eugene W. Hilgard as its first director. The passage of the
Hatch Act in 1887 and the second Morrill Act of 1890
provided additional support for agricultural science
(TRUE 1937). Hilgard and the Regents of the University
of California decided to establish four ‘regional culture’
stations in the state’s four main climatic regions (STADTMAN 1970, NYE 1983). However, the experiment station
3
rank 5th, 17th, and 30th, respectively, among the top 50
California agricultural export commodities. The total
1997 export value for oranges, lemons, and grapefruit
was about $454 million (CALIFORNIA DEPT. OF FOOD
AND AGRICULTURE 2000).
California enjoys a distinct advantage over other
citrus-producing areas of the world in terms of being able
to deliver fresh fruit to the market virtually every day of
the year. This is by virtue of California’s diversity of
mesoclimates, allowing a mix of citrus varieties to be
grown successfully in several distinct areas which are
scattered from the Sacramento Valley in the north to
San Diego County in the south.
The five main areas of production are: 1) the
southern and central San Joaquin Valley, which encompasses portions of Kern, Tulare, Fresno, and Madera
counties; 2) the coastal counties of San Diego, Orange,
Ventura, Santa Barbara, and, to a lesser extent, San Luis
Obispo and Monterey); 3) an inland area including
western Riverside and San Bernardino counties; 4) low
elevation desert areas of Coachella, Palo Verde, and Imperial Valleys; and 5) a relatively small northern California area that includes parts of Butte, Glenn, and Yolo
counties in the Sacramento Valley.
The combination of low humidity and varied climatic conditions enables growers in California to produce citrus which is consistently good in terms of both
eating quality and appearance. Accordingly, the crop is
grown primarily for fresh consumption, but excess fruit
or fruit not meeting fresh fruit standards is utilized for
juice and other processed products.
of the Citrus Experiment Station to the Citrus Research
Center and Agricultural Experiment Station (CRCAES). Today, the CRC-AES makes the largest commitment of any organization in California to citrus genetics,
breeding, physiology, and postharvest research.
ECONOMIC VALUE OF CITRUS TO
CALIFORNIA
THE COMMERCIAL PRODUCTION OF citrus in California
has grown tremendously since the mid-1800s. Today,
almost 275,000 acres are devoted to citrus, yielding
about 4.5 billion pounds of fruit annually. California accounts for 82 percent of the lemons produced in the
United States and is second only to Florida in the production of other major citrus types which include the
oranges, grapefruits, mandarin, mandarin hybrids, and
limes. In 1999, the most recent year for which comprehensive data are available, the gross on-farm value of
California citrus was about $734 million (CALIFORNIA
AGRICULTURAL STATISTICS SERVICE 2000).
The leading types of citrus produced in California
are oranges, lemons, and grapefruit, but mandarins and
hybrids including tangelos and tangors are also gaining
in importance. Oranges and lemons ranked 14th and
22nd, respectively, in 1999 among California agricultural
commodities. Figures from 1999 put the gross on-farm
value of navel and Valencia oranges combined at $416
million, followed by lemons at $214 million, grapefruit
at $81 million, and mandarins and hybrids at about $23
million. (CALIFORNIA AGRICULTURAL STATISTICS SERVICE 2000).
California is the sixth largest exporter of agricultural products in the world and citrus is a major contributor to that volume. Oranges, lemons, and grapefruit
Original Citrus Experiment Station staff on
the steps of the Rubidoux Laboratory building ca. 1916.
This was the first home of the Citrus Experiment Station. Front row from left: C.O. Smith, J.T. Barrett, L.D.
Batchelor, H.S. Reed, W.P. Kelley, and H.J. Webber;
Back row from left: H.J. Quayle, E.E. Thomas, W.M.
Mertz, H.B. Frost, H.S. Fawcett, W.D. Drew, and R.S.
Vaile. Photo courtesy of Special Collections, Tomás
Rivera Library, University of California, Riverside.
Figure 2.
December 23, 1914 headlines from the Riverside Daily Press announcing that the expanded Citrus
Experiment Station was awarded to Riverside, California. Photo courtesy of Special Collections, Tomás Rivera
Library, University of California, Riverside.
Figure 1.
4
polymorphism (RFLP) and random amplified polymorphic DNA (RAPD) molecular markers shows that citrus
accessions of hybrid origin can be identified, likely parents of hybrids can be identified, instances of gene introgression can be identified, and some differences between
the Swingle and Tanaka systems can be resolved (FEDERICI et al. 1998). The motivation for studies on citrus
species definition and relationships is not limited to understanding phylogeny. Accurate knowledge about phylogenetic relationships can guide searches of genetic
resources collections for specific genes. An example is a
recent successful search of citrus accessions for new
sources of resistance to the citrus tristeza virus (CTV)
(MESTRE et al. 1997b) which causes one of the most
damaging diseases in citrus crops worldwide.
Figure 3. A cultivation demonstration at Riverside, ca.
1917. The structures in the background are the main
laboratory and south wing of the Citrus Experiment Station building made possible by the expansion of the CES
to its new location authorized in 1914. Photo courtesy of
Special Collections, Tomás Rivera Library, University of
California, Riverside.
BIOLOGY OF CITRUS
CITRUS IS WIDELY CULTIVATED throughout the tropical,
subtropical, and borderline subtropical-temperate climatic regions of the world, and is one of the world’s major fruit crops. Most of the fruits commonly referred to as
citrus are classified in the genus Citrus. The genus Citrus
and 32 related genera belong to the subfamily Aurantioideae of the Rutaceae plant family. Diploid Citrus species have 9 pairs of chromosomes (2x=2n=18) and there
are some tetraploid (4x=2n=36) and triploid (3x=27)
accessions.
Most citrus species are diploid, that is, they have
two genomes (sets of chromosomes), one genome inherited from each parent. In citrus a genome consists of
nine chromosomes, therefore a diploid species will have
18 chromosomes. However, a low percentage of citrus
seedlings are polyploid, that is, they have more than two
genomes. For example, a species with four genomes is
referred to as tetraploid. Very few citrus cultivars are
polyploid, but those that are have been exploited by
plant breeders in attempts to produce seedless fruit.
When a tetraploid seed parent is crossed with a diploid
pollen parent, the anticipated result is triploid progeny
(three genomes) which produce seedless fruit due to the
lack of functional gametes. Seedless fruit is possible because a number of citrus types are parthenocarpic which
means they have the ability to produce fruit without pollination and/or seed development. Much of the information about the genetics and crossing relationships in the
genus Citrus is a result of knowledge accumulated over
the 80 plus years that citrus breeding has been conducted at UC Riverside.
Nearly all cultivars within the orange, grapefruit,
and lemon groups are believed to have originated either
by selection of budsports, which are mutations that arise
in single somatic cells in a branch, or by selection of nucellar seedlings (SOOST and ROOSE 1996). Nucellar
seedlings are derived from somatic embryos which originate from cell division in the ovary, outside the embryo
sac (Figures 4 and 5). Since these nucellar embryos de-
TAXONOMY OF CITRUS
FOR THE GENUS CITRUS, there are several taxonomic
treatments defining and ordering the component species.
The Swingle system (SWINGLE 1943, SWINGLE and
REECE 1967) recognizes 16 species. There are also modifications which recognize varying numbers of species: 17
species (BHATTACHARYA and DUTTA 1956, STONE
1994), 36 species (HODGSON 1961), or 31 species
(SINGH and NATH 1969). The Tanaka system recognizes
up to 162 species (TANAKA 1977). It has also been suggested that there are only three valid species of cultivated citrus (C. medica, C. reticulata, and C. maxima)
(SCORA 1975, BARRETT and RHODES 1976).
The Swingle system is more widely accepted than
the Tanaka system and will be used in this report. According to the Swingle system, the genus Citrus is divided into the subgenera Papeda, with six species, and
Citrus, with 10 species. Subgenus Citrus includes the cultivated types commonly referred to as citron, grapefruit
(or pomelo), lemon, lime, mandarin, pummelo (or shaddock), sour orange, and sweet orange.
The lack of agreement on a single taxonomic system reflects the complexity of citrus-type species. Opinions differ as to what justifies species status and whether
or not supposed hybrids among naturally occurring forms
should be assigned species status. It also is a manifestation of taxonomic treatments that must rely on morphological and biochemical characters (phenotype) without
having data on the genetic relationships of the organisms being classified. Features of citrus biology have produced an array of actual and apparent genetic diversity.
Molecular techniques that reveal the genetic relationships of genes and genotypes from one individual or type
to another are providing the genetic evidence that will
enable the development of taxonomic systems that more
clearly reflect phylogeny and evolutionary history. For
example, a recent study using restriction fragment length
5
velop asexually, with no male cells contributing to their
formation, they are expected to be genetically identical
to the seed parent. This means that, despite having
many named cultivars, there is relatively little genetic
diversity within the orange, grapefruit, and lemon
groups. In contrast, in the mandarin, pummelo, and, to a
lesser extent, citron groups, many cultivars have arisen
by sexual hybridization and levels of genetic diversity
within these groups are much higher (ROOSE et al.
1995). Table 1 summarizes our current understanding of
the origin, mode of reproduction, and level of genetic
diversity within these commercially important taxa. Under Swingle’s taxonomic system, some of these ‘species’
include cultivars derived from several different interspecific hybrids. Thus, the lemon group includes the cultivated lemon in which most cultivars are derived from a
single ancestor by mutation, but many others within the
group are hybrids, possibly having at least one parent in
common with the cultivated lemon. These hybrids include rough lemon, Meyer lemon, the limettas, karna,
and others. In addition, there are many citrus species
that are more distantly related to the cultivated groups,
and which represent additional genetic diversity. Such
groups include C. ichangensis, other subgenus Papeda species, and C. halimii.
trifoliate orange and kumquat are found in a line crossing south-central China in an east-west direction. More
recently, GMITTER and HU (1990) have proposed that
Yunnan, China, through which the Tanaka line runs, is
itself a major center of origin for citrus. Some related
Aurantioideae genera are native to Asia, Africa, and
Australia.
DOMESTICATION OF CITRUS
THERE IS LITTLE EVIDENCE for the timing of the domestication of citrus. Where ‘natural’ populations are located,
it is often difficult to determine whether they represent
wild ancestors or are derived from naturalized forms of
introduced varieties. Most authorities agree that citron,
mandarin, and pummelo are most similar to the ancestors of modern cultivated types. These species all reproduce sexually and if different cultivars within these species are hybridized, the progeny are relatively similar to
their parents. The other important cultivated types, including orange, grapefruit, lemon, and lime, are believed
to have originated by one or more generations of hybridization among these ancestral types (ROOSE et al. 1995).
The precise ancestry of these groups is not known.
GENETIC DIVERSITY OF CITRUS
ORIGIN AND DISTRIBUTION OF CITRUS
ONE GOAL OF CONSERVATION is to capture and maintain
genes responsible for traits important for human use.
The visible or tangible diversity in plants (phenotypic
diversity) usually reflects underlying genetic diversity.
What may not be apparent, however, is the complexity
of the genetics governing specific observable phenotypes. Highly diverse phenotypes may be closely related
genetically, with the divergence due to one or two critical gene differences. Phenotypic diversity is still the criterion most often used to characterize genetic resource
collections, however, molecular technologies to define,
determine, and monitor genetic diversity are rapidly being adopted for citrus and other crops.
The most obvious traits for which phenotypic diversity is apparent in citrus and citrus relatives is fruit
CITRUS AND RELATED GENERA are native to southeast
Asia (northeastern India, southern China, and the
Indochinese peninsula). This is the center of diversity
and most probable area of origin for these species
(DAVIES and ALBRIGO 1994). TANAKA (1954) proposed
a theoretical line (the Tanaka line) which runs southeastwardly from the northwest border of India, above
Burma, through the Yunnan province of China, to south
of the island of Hainan. Citron, lemon, lime, sweet orange, sour orange, and pummelo originated south of this
line, while mandarin, kumquat, and trifoliate orange
originated north of the line. Mandarin apparently developed along a line northeast of the Tanaka line, along the
east China coast, through Taiwan, and to Japan, while
Table 1.
Summary of taxa in subgenus Citrus.
Common name
Species name
Citron
C. medica
Known age
(years)
Probable origin
Seed
reproduction
Genetic
diversity
2300
nonhybrid
sexual
moderate
Grapefruit
C. paradisi
200
hybrid
nucellar
low
Lemon
C. limon
800
hybrid
partly sexual
moderate*
Lime
C. aurantifolia
700
hybrid
partly sexual
moderate*
Mandarin
C. reticulata
unknown
nonhybrid
variable
high
Pummelo
C. maxima
unknown
nonhybrid
sexual
high
Sour orange
C. aurantium
900
hybrid
nucellar
low
Sweet orange
C. sinensis
500
hybrid
nucellar
low
*This extent of genetic diversity is due to combining different interspecific hybrids under a single species name.
6
size and morphology (Figure 6). For example, fruit ranges
in size from that of the pummelo which may be as large
as a person’s head and weigh many pounds to that of the
Chinese box orange, Severinia buxifolia, which is as small
as a pea and weighs only a fraction of an ounce. Most
fruits are either round, slightly flattened, or elongated in
shape, but those of the orange jessamine (Murraya paniculata) are oblong and small and those of the Australian
finger lime (Microcitrus australasica, Figure 7) are very
long and banana shaped.
Although most trees of citrus and citrus relatives
are evergreen, the trifoliate orange, Poncirus trifoliata,
sheds its leaves during the winter. There is tremendous
variation in leaf size and shape among the species of the
subfamily. Most types have a simple, single leaf which
may be long and narrow, but others have compound
leaves with three or more leaflets.
Diversity is also apparent in the variety of uses of
citrus and citrus relatives by humans. The flesh of citrus
such as lemons, limes, oranges, and pummelos are commonly consumed as fresh fruit or juice, but the flesh of
citrons is very acidic and generally not consumed. However, the rind is commonly used to make candied citron
peel and fruitcake ‘fruit’. In contrast, the leaves of Citrus
hystrix (see inside front cover) are consumed as herbs for
cooking in the Philippines and Thailand due to their
highly aromatic and volatile oils. Both the leaves and
flesh of the sour orange have numerous medicinal uses in
Asia and South America. In Japan and China, immature
and mature fruits of sour orange are common medicinals
considered to regulate vital energy and remove phlegm.
In Haiti, sour orange leaves and fruits are also used in
food preparation, agriculture, construction, and voodoo
as well as for 10 different medicinals (PAUL and COX
1995). These are just a few of the many uses of citrus and
citrus relatives around the world.
Diversity within citrus and citrus relatives can also
be illustrated by the differences in disease resistance
among them. For example, mandarins are symptom-less
carriers of CTV. In contrast, limes are so susceptible to
this virus that they are used as indicator plants for the
disease. Trifoliate orange is a source of genetic resistance
to CTV.
In addition to the use of molecular techniques to
elucidate phylogeny as described above, several techniques have been successfully applied to citrus to determine the genetic architecture of citrus genomes, evaluate the genetic basis for traits, determine the extent of
genetic variability within and between citrus types, identify specific genotypes, and link phenotypic traits to molecular markers.
It is important for plant breeding, genetic resource
maintenance, and commercial production of crops to be
able to unequivocally identify important genotypes and
to distinguish them from others that may be phenotypically similar. Molecular markers are useful for these purposes (ROOSE 1988, Figure 8). Inter-simple sequence repeat markers were recently shown to distinguish among
several closely related citrus cultivars (FANG and ROOSE
1997). These markers, in conjunction with isozymes and
RFLPs, will provide the needed tools to ‘fingerprint’ citrus accessions (FANG et al. 1997b), even closely related
ones that differ by mutations in a few genes. DNA fingerprinting techniques are also proving to be valuable for
defining and monitoring genetic diversity in the citrus
subfamily and in citrus genetic resource collections
(HERRERO et al. 1996a,b, FANG et al. 1997b).
One example of the use of markers is the current
understanding of the genetics of resistance to CTV in
trifoliate orange, which was initially thought to be controlled by a single dominant gene. Genetic linkage maps
of the region surrounding the CTV resistance gene have
been developed (GMITTER et al. 1996, FANG et al. 1998)
and recent work with RAPD molecular markers indicates that at least one other gene is involved (MESTRE et
Figure 4. Microscopic cross-section of developing seed
revealing the multiple nucellar embryos contained
within (polyembryony). Photo credit: Joseph L. Kepiro.
Figure 5. Germinating seeds revealing the multiple nucellar seedlings emerging from the seed at the left (polyembryony). Photo credit: Joseph L. Kepiro.
7
al. 1997a). Molecular markers will enhance the use of
these resistance genes in citrus rootstocks and cultivars
and may ultimately be used to clone and sequence genes.
Molecular markers were used to discover CTV resistance
in Fortunella crassifolia which is much more closely related to commercial citrus species than trifoliate orange
is, promising a route for gene transfer by sexual hybridization (MESTRE et al. 1997b). Another example of a
molecular marker involves a gene that controls fruit
acidity, a highly variable, commercially important phenotypic citrus trait. Three RAPD markers were found to
be tightly linked to this gene and will allow early selection for this trait in citrus breeding programs (FANG et
al. 1997a).
low-acid pummelo accession (CRC #2240) was the parent of two early-maturing, triploid pummelo-grapefruit
hybrids, ‘Oroblanco’ (1980) and ‘Melogold’ (1985), and
a hybrid pummelo ‘Chandler’ (1961). See SOOST and
ROOSE (1996) for a review of citrus breeding.
Development of these low-acid varieties provides
an excellent example of the value of genetic resources
and their use in crop improvement. The low-acid pummelo parent accumulates virtually no citric acid in juice
vesicles, and consequently has flavor that many consider
‘insipid’, although such fruit are prized in some cultures.
Hybrids between the pummelo CRC #2240 and highacid varieties such as grapefruit, orange, or pummelo
have intermediate acidity levels and early maturity.
Thus, genetic resource accessions that have little commercial value can be valuable as parents in breeding new
cultivars.
Rootstock breeding was initiated in the 1950s at
UC Riverside. Trifoliate orange has been the source of
resistance to citrus nematode and Phytophthora root rot
and gummosis (Figure 11). During the 1950s, CTV became widespread in southern California and killed millions of trees on sour orange rootstock. Hundreds of accessions in the CVC were tested for their performance as
rootstocks for scions infected with CTV (Figure 12).
Many accessions with acceptable tolerance were identi-
UTILIZATION OF GENETIC RESOURCES IN
CALIFORNIA
THE DEVELOPMENT OF NEW VARIETIES through breeding
is the major direct use of citrus genetic resources. Breeding at the UC Citrus Research Center, Riverside was
begun in 1914 by H.B. Frost (Figure 9). Of the several
species and varieties used, ‘King’ mandarin proved to be
an outstanding parent. Three King hybrids, ‘Kara’ (=
‘Owari’ Satsuma × King), ‘Kinnow’ (= King × ‘Willowleaf’), and ‘Wilking’(= King × Willowleaf) were introduced in 1935. These and other hybrids from the first
series of crosses were used in further breeding. Beginning
in the late 1940s crossing was expanded in three areas:
1) use of mandarin hybrids such as tangelos and tangors
as parents, 2) crossing tetraploids with diploids to produce triploids (which are seedless), and 3) crosses of
pummelos with mandarins, grapefruit, and other pummelos. Two mandarin hybrids, ‘Encore’ and ‘Pixie’, were
introduced in 1965 and most recently, in 1999, the mandarin hybrid ‘Gold Nugget’ was released (Figure 10). A
Figure 6. The strikingly distinct fruits of Buddha’s hand
citron (Fingered citron, Citrus medica, CRC #3768) is
highly valued in Japan and China where it is used for
perfuming rooms and clothing and as an offering on altars. The fruit is a horticultural curiosity due to its shape
which resembles a human hand, lack of flesh, and fragrant peel which can be candied for use in fruit cakes or
as a garnish. Photo credit: Ottillia J. Bier.
Figure 7. Fruit and branch of Australian finger lime
(Microcitrus australasica, CRC #1484). The species is endemic to the subtropical coastal region of eastern Australia and is used as ‘bushfood’. It has been investigated
for its contribution to rootstock breeding. Photo credit: J.
Rick Martin.
8
fied and some are used either as rootstocks or parents for
rootstock breeding (Figures 13 and 14). These experiments also resulted in identification of ‘Flying Dragon’
trifoliate orange (Figure 15) as a dwarfing rootstock for
citrus, another example of the value of a well-characterized genetic resources collection. Two citranges from the
UCR breeding program, C32 and C35, were released for
trial as rootstocks in 1986. Both have resistance to citrus
nematode, Phytophthora, and CTV. C35 is currently
widely used in California because of its combination of
excellent disease resistance, moderate tree size, and high
productivity relative to tree size.
A smaller-scale citrus breeding program was developed starting in 1948 at the USDA Date and Citrus Station in Indio, California. The objectives were the production of high-quality mandarin types; an early maturing, high-quality sweet orange; cold-hardy varieties; red
grapefruit of improved color; a virus-free ‘Temple’ orange
type; and rootstocks with particular characteristics, such
as tolerance to saline soils and Phytophthora root rot
(FURR et al. 1963, FURR 1969). This program was supported by a collection of over 200 accessions, the most
valuable of which were incorporated into the CVC or
other UCR plantings when the Indio station closed in
1982. This program lead to the release of ‘Fairchild’,
‘Fremont’, and ‘Fortune’ mandarins (FURR 1964), ‘Reinking’ pummelo, ‘Schaub’ rough lemon, ‘African shaddock × Rubidoux trifoliate’, and ‘Rangpur × Troyer’
rootstocks.
Breeding new cultivars is an ongoing effort at UC
Riverside in California and by researchers in Arizona
and Florida. Many crosses are made using accessions
within the CVC. In addition, field trials are presently
being conducted on many rootstock and scion hybrids
from the breeding program. Recent crosses for rootstock
breeding include pummelo × trifoliate, taiwanica × trifoliate, trifoliate orange selfed, crosses between trifoliate
hybrids, and crosses between trifoliate hybrids and citrus.
Recent crosses for scion breeding involve various tetraploid mandarins, oranges, and grapefruit crossed with diploid mandarins and pummelos. There is a continued effort
to develop early maturing cultivars with low fruit acidity
using the gene originally found in pummelo CRC #2240.
In the future, development of new cultivars will
involve a wide range of techniques that will enhance our
ability to manipulate citrus genetic resources. The creation of new hybrids by performing crosses and the selection of promising hybrids from these crosses will continue to be used to create varieties with novel combinations of traits. The power of this method will be increased by marker-aided selection of hybrid seedlings
that are likely to have desirable traits. In this technique,
hybrids are selected at the seedling stage based on their
genotype for molecular markers that are inherited with
desired genes. For example, DNA markers that allow
marker-aided selection for the low-acid gene have been
identified (FANG et al. 1997a). A high proportion of
Figure 8. Example of diversity at the molecular level:
Each vertical lane contains DNA from a different germplasm accession. A short DNA sequence was amplified,
hybridized with the DNA of these accessions, and visualized by tagging with a fluorescent dye. The fragments of
different sizes that the dye reveals are the dark areas
(bands) in the lanes. Among these accessions there are
five different bands revealed by this analysis. Differences
in number and pattern of bands from lane to lane indicate genetic diversity among the accessions. Photo credit:
Noelle A. Barkley.
Figure 9. Howard B. Frost (l.), first citrus breeder at UC
Riverside (beginning in 1914) and Robert K. Soost, who
succeeded Frost as citrus breeder in 1949 and was a curator of the CVC from 1982 until 1986. Frost’s hybrid citrus varieties and nucellar budlines revitalized the California citrus industry. Soost worked on nucellar embryony and citrus cytology and released several commercially successful citrus varieties. Photo courtesy of Special Collections, Tomás Rivera Library, University of
California, Riverside.
9
progeny having this gene can be identified without
growing the hybrids to fruiting, a long and costly process.
Marker-aided selection is already used in citrus breeding
programs and will become more important as markers
linked to additional genes are identified. It increases the
efficiency of breeding programs because those hybrids
grown into trees for evaluation can be preselected for
one or more desirable traits, increasing the likelihood
that hybrids with commercially acceptable combinations
of traits will be identified.
The direct introduction of DNA (transformation)
is also beginning to be used for citrus improvement
(GMITTER et al. 1992, BOND and ROOSE 1998). Specific
genes can be added to existing cultivars using genetic
engineering methods that are now established for some
important citrus varieties. This technique can be used to
correct defects in existing cultivars with minimal alteration of other characters, an objective that is difficult or
impossible by hybridization-selection methods because of
the long generation time and high heterozygosity of
most citrus. Each individual has two copies of each gene,
one received from each parent. If both copies are the
same, the individual is said to be homozygous for that
gene. If they are different, the individual is heterozygous
for that gene. The greater the number of genes for which
an individual has differing copies, the more heterozygous
that individual is. Many citrus cultivars are highly heterozygous because they originated by interspecific hybridization. Consequently, each parent contributes quite
different versions of many genes and few progeny from
such crosses are similar to their parents. Thus it is extremely difficult to develop new orange varieties or correct
defects in existing ones by hybridization and selection.
Transformation increases the economic importance of citrus genetic resources because it allows breeders to use genes from accessions that are difficult to use
as parents because of sterility or cross incompatibility or
because they contribute commercially undesirable traits
to hybrids. A good example of the difficulties encountered in such projects are attempts to develop cold-hardy
citrus by hybridization with a cold-hardy relative, the
Figure 10. Fruit and branch of Gold Nugget mandarin
orange (CRC #3913) released by M.L. Roose in 1999,
resulting from work initiated by R.K. Soost and J.W.
Cameron with a selection made in 1975. It is one of
many successes of the Citrus Breeding Program at UCR
to which accessions maintained in the CVC have contributed. Photo credit: J. Rick Martin.
Figure 11. Trunk of root-stock showing damage from
Phytophthora infection: blistering and cracking of bark
caused by damage in the active growing layer (cambium). Photo credit: Ottillia J. Bier.
10
trifoliate orange. Breeders have been crossing trifoliate
orange with citrus and selecting among the progeny to
develop cold-hardy citrus varieties since about 1900. In
1988, the USDA program in Orlando, Florida released a
backcross hybrid considered to have ‘moderate edibility’
(BARRETT 1990). Additional generations will be required to achieve commercially acceptable fruit. If the
individual genes responsible for cold-hardiness can be
identified and cloned, it should be possible to transfer
them to citrus cultivars. Other targets for transformation
are the genes for disease and insect resistance, salinity
tolerance, and many other important traits that exist in
citrus relatives, but cannot currently be exploited for
cultivars by hybridization-selection methods. Research
by the UC Riverside citrus breeding program is underway to identify and clone a trifoliate orange gene for resistance to CTV.
sources are in reality biological information passed down
through generations in an unbroken chain (WILKES
1988). Once this chain is broken that unique resource is
lost forever. This has lead to the necessity of protecting
and preserving plant genetic diversity for current and
future use.
The success of fruit and nut breeding programs in
the US has largely been due to the accessibility of a wide
range of genetic resources. Since much of the world’s
valuable fruit and nut genetic resources originated as
wild species outside the US, it is important that breeders
have access to these important resources through importation and maintenance in collections. For California,
the optimum situation is to have the genetic resources
accessible from collections maintained in the state.
Readily available genetic resources have enhanced the
progress of citrus breeding in California as described
above. The CVC accessions have provided parents and
sources of individual genes used in the breeding program.
The more well-characterized the accessions are, the
more efficient it is to select parents for crosses. Projects
such as investigating the phylogeny of citrus taxa
(FEDERICI et al. 1998) could not have been done if the
researchers had not had at hand the diversity of genetic
material maintained in the CVC.
‘Wild’ citrus populations are relatively rare. Most
often wild citrus exists as scattered trees in remote areas,
as opposed to pure-stand populations. Citrus trees incur
IMPORTANCE OF CITRUS GENETIC
RESOURCES CONSERVATION
THE GENETIC DIVERSITY OF PLANTS, developed by evolution, hybridization, and manipulation by humans, provides the basis for the food production which supports
the world’s population. This diversity is threatened by
numerous complex factors including human encroachment on natural ecosystems and the shift to cultivation
of a smaller number of advanced lines. Plant genetic re-
Figure 12. Trunk
with bark removed
to reveal damage
caused by the citrus
tristeza virus (CTV):
the lower grooved
and scarred region is
the damaged rootstock. Photo credit:
Ottillia J. Bier.
Figure 13. Successful graft: the scion (upper part) is the desired fruit variety and
the rootstock (lower part) is a genotype
selected for specific disease or pest resistance, environmental tolerance, or horticultural characteristics. Photo credit:
Ottillia J. Bier.
11
Figure 14. An incompatible graft shown
with bark stripped away: the scion has
overgrown the rootstock at the graft juncture. Photo credit: Ottillia J. Bier.
CENTER FOR PLANT CONSERVATION 1991, NATIONAL
RESEARCH COUNCIL 1993). Similar losses have occurred
in existing plant collections through inadequate maintenance.
In the future, the need for maintenance of citrus
genetic resources will become even greater because development and habitat loss in the tropical and subtropical areas where citrus is native will continue to erode
genetic diversity. Obtaining previously collected genetic
resources from other countries is also becoming more
difficult as genetic resources are increasingly seen as
commodities that should only benefit the nation in
which they are native or be made available to other
countries at a price.
mutations and many types hybridize readily. Some types
reproduce true-to-type from seed due to nucellar embryony. In addition, for thousands of years humans have
selected lines with desirable characteristics and preserved them by vegetative propagation. These factors have
led to the perpetuation of ‘elite’ lines, frequently at the
expense of the progenitor wild types.
Aurantioideae genera other than the genus Citrus
are utilized much less frequently and therefore exist most
often as wild, unselected types. These 32 genera, mostly
tropical, are generally not sexually compatible with Citrus and are of limited commercial importance. Consequently, they have received little attention except from
local inhabitants. It is in these genera, located in more
remote areas, that the threat of loss of genetic diversity
through habitat destruction is greatest.
It is generally conceded that there is much genetic
erosion in both wild and cultivated members of the Aurantioideae, but there are few hard facts available to illustrate this and in most cases there is no clear insight into
how much genetic variability has been lost and what the
value of the lost materials may be. This lack of knowledge should not preclude the collection and preservation
of threatened materials.
Preservation of the genetic diversity represented in
plant ecosystems throughout the world has become a
major issue of international concern. The loss of increasingly large numbers of plant species through habitat destruction threatens the availability of a diverse plant genetic resource base which will be needed for future generations (HOLDEN and WILLIAMS 1984, RAVEN 1988,
ACQUISITION OF CITRUS GENETIC
RESOURCES
WHILE THE DIVERSITY OF CITRUS genetic resources already maintained in California is great, there are several
reasons that new material needs to be acquired. For example, specific genotypes (e.g., with disease resistance or
environmental tolerances) or cultivars may not be present in California and thus need to be imported. Exchange of materials with other collections outside of
California is one route that may produce new genetic
resources. Collection expeditions to sites of wild citrus
diversity is another. In general, new material may potentially be obtained from existing collections, from commercial sources, or from wild or semi-wild populations.
An important concern when moving genetic resources from one location to another is the potential of
inadvertently introducing associated pathogens into a
geographic area where they were originally absent. There
are different amounts of risk associated with different
sources of materials. There generally is less risk associated with obtaining materials from an established collection or certification program than from a commercial
source or the wild. However, a number of scientific and
ethical issues need to considered and addressed when
plant exploration is to take place (BENNETT 1970,
HAWKES 1980, NAMKOONG 1988, PLANT EXPLORATION
OFFICE 1990, GUARINO et al. 1995, and HOAGLAND
and ROSSMAN 1997).
The USDA Animal and Plant Health Inspection
Service (APHIS) is responsible for preventing pests from
foreign sources from entering the US (USDA-APHIS
1977, 1988, 2000). The general guidelines and procedures for importing plant materials into the US are outlined by PARLIMAN and WHITE (1985) and FOSTER
(1988). Suggestions specific to citrus are detailed in
KNORR (1977), ROISTACHER et al. (1977), FRISON and
TAHER 1991, and NAVARRO (1993).
For citrus, the need for pathogen-free and/or tested
propagative budwood has long been recognized as crucial
to the establishment and maintenance of a viable citrus
industry. Virus, viroid, and mycoplasma pathogens in
Figure 15. Hiryu (Flying Dragon trifoliate orange,
Poncirus trifoliata, CRC #3795) is a dwarfing rootstock in
citrus production and is a source of genetic resistance to
citrus tristeza virus and other citrus pathogens. Photo
credit: Ottillia J. Bier.
12
be found in USDA-ARS (1968), ROISTACHER (1991,
1998), and IOCV (nd). The Rubidoux Quarantine Facility includes laboratory facilities and an insect-proof
greenhouse with temperature and light controls which
are required for biological indexing. This facility is located in the city of Riverside but isolated from the nearest commercial orchards and the UCR experimental orchards by about three miles.
Typically, when a new import is received by CCPP,
four propagations are made of that budline on Rough
Lemon rootstock to preserve the budline and produce
budwood for future indexing and/or therapy. The remaining portion of the import budline is used to graft
inoculate indicator seedlings in a screening called the
pre-index, which will indicate if the import budline is
infected with CTV, psorosis, or citrus viroids. A very
high percentage of new imports arrive infected with one
or more of these diseases.
If the pre-index shows that the newly introduced
variety is infected, it must be subjected to therapy procedures which can eliminate the disease or diseases from
the budline (ROISTACHER 1991, NAVARRO 1992). The
CCPP employs two methods of therapy: thermal therapy
and shoot-tip-micrografting. Thermal therapy (CALAVAN et al. 1972, ROISTACHER 1977) involves subjecting
infected buds to high temperatures (40ºC) for several
months. This has proven to eliminate some graft-transmissible diseases from an infected budline. Shoot-tipmicrografting (MURASHIGE et al. 1972, NAVARRO et al.
1975, NAVARRO and JUAREZ 1977, NAVARRO 1981a,b)
is a procedure in which several apical meristems from
new growth tips are taken from an infected import plant
and grafted into a healthy seedling grown under aseptic
conditions, and subsequently grown in vitro until it is
large enough to graft onto a conventional rootstock
seedling. If small enough when removed, the apical meristem does not contain the disease. This method has
proven superior to thermal therapy in eliminating some
pathogens, particularly the viroids. However, some
pathogens are better eliminated by thermal therapy, so
often both techniques are used.
Following therapy, the material must again undergo thorough indexing to determine the presence or
absence of disease. If subsequent testing shows that disease is still present, then the plant material must again
be subjected to therapy. When a budline tests negative
in the pre-index or after therapy, it enters the Variety
Introduction (VI) Index. All materials are indexed for
cachexia, Citrus-associated viroids, citrus exocortis,
CTV, concave gum, greening, infectious variegation,
psorosis, stubborn, tatterleaf, and vein enation/woody
gall. Depending upon the country of origin various other
diseases may be assigned. For instance, materials entering from Australia are also tested for blight.
If a budline is shown to be free of known diseases
in the VI Index, it is considered to be ready for release
from quarantine. CCPP will then apply for its release
propagative budwood can be deleterious to tree survival
and fruit production. These pathogens can be easily distributed by infected plants, infected budwood, or vectors
to areas free of them, where they become a potential
hazard to existing and future plantings. Consequently,
any new varieties introduced must be thoroughly tested
for the presence of pests and pathogens before being released to the public. Because of these factors, citrus materials are one of the most highly regulated plant materials in respect to international exchange, or even exchange between different states.
The introduction of new citrus varieties to California is a cooperative venture involving federal, state, and
county departments of agriculture and the University of
California. The CCPP has an import permits issued by
APHIS and the California Dept. of Food and Agriculture (CDFA) which allow, with specific requirements,
the importation of citrus budwood. The Federal and
State requirements are enforced by APHIS, CDFA, and
California County Agricultural Commissioners.
Foreign citrus material entering the US passes
through Beltsville, Maryland and is inspected by APHIS
for the presence of soil and pests. If clean, the material is
sent on. Seeds may be sent directly to any requestor,
such as the UCR Citrus Breeding Program, CVC, or
NCGRCD, but all vegetative materials entering California must be sent to CCPP and quarantined there before
being released to the public. In the past, quarantining of
citrus vegetative materials was done in Glenn Dale,
Maryland, at the Plant Germplasm Quarantine Office,
which was recently relocated to Beltsville. This facility is
responsible for all plant introductions to the US, and is
overburdened with a large backlog of materials that require
testing and cleanup. Consequently, it has evolved over the
years that almost all citrus vegetative materials entering
the US are sent directly to CCPP for quarantining.
The CCPP procedure for importation and distribution of disease-free propagative citrus materials starts
with a comprehensive indexing program to detect grafttransmissible diseases which may arrive in an imported
budline. Detection of graft-transmissible diseases of citrus is based primarily on biological indexing by grafting
tissue from the import test source to specific citrus indicator seedlings. Specific indicator seedlings are used to
detect specific diseases and have been selected over the
years for sensitivity to disease and ability to express disease symptoms. In each index, adequate positive and
healthy control seedlings of each indicator variety are
held under the same environmental conditions as the
test source seedlings, and are used for comparison with
the test source. Complementing this biological testing
are laboratory test techniques including: enzyme-linked
immuno-sorbant assay (ELISA) for the detection of
CTV, sequential polyacrylamide gel electrophoresis for
the detection of citrus viroids (exocortis/cachexia), and
culture in growth media for detection of stubborn disease. More detailed information on these procedures may
13
citrus seeds is still rare (MUMFORD and GROUT 1979),
however, progress has been made and preliminary guidelines are forthcoming (C. VERTUCCI-WALTERS, 1995
personal communication).
Trees such as citrus are considered to be ‘clonal’
crops because they are usually propagated from vegetative tissues since individual trees are often highly heterozygous and do not reproduce true-to-type from seeds.
Preservation of genetic resources of clonal crops presents
a different set of challenges and techniques than does
preservation of seed crops (SAKAI 1984, 1995; TOWILL
1988, 1989; TOWILL and ROOS 1989; BAJAJ 1995).
There are only a few reports of successful cryopreservation of embryonic axes (RADHAMANI and CHANDEL
1992), embryos (MARÍN and DURÁN-VILA 1992, MARÍN
et al. 1993), ovules (BAJAJ 1984), and cells (KOBAYASHI
et al. 1990, DURÁN-VILA 1995, SAKAI 1995). Pollen
storage has been marginally successful in citrus (SAHAR
and SPIEGEL-ROY 1980) but newer research (NIEDZ et al.
1992) shows greater storage success using freeze-drying
and cryostorage. DURÁN-VILA (1995) has reviewed
cryopreservation of citrus genetic resources in general.
Cryopreservation has not yet proved to be a practical
conservation method for citrus. Trifoliate orange is likely
to be the first citrus genetic resource that will be successfully stored at cryogenic temperatures (L TOWILL, 1996
personal communication).
The maintenance technique of choice for citrus
genetic resources continues to be ex situ plantings of living trees in orchards or in more controlled environments
such as greenhouses or screenhouses. Horticultural challenges to this procedure include pest control, irrigation,
fertilization, pruning, and appropriate repropagation.
Field trees are necessary for evaluation purposes and as a
seed source, but are subject to the vagaries of weather
and must be considered to be of unknown disease-status
unless rigorously tested at regular intervals. Trees maintained in greenhouses are more secure from an environmental standpoint and may be more readily kept in a
disease-free state, but are not suitable for evaluation and
must of necessity remain rather small in size. Maintenance of a collection in a screenhouse represents a compromise between a field collection and a greenhouse collection. Ideally, a citrus genetic resources collection
should include both a field planting, for evaluation purposes and as a seed source, and a protected block for the
production of virus-free budwood.
from both state and federal quarantine. The CCPP must
first obtain release from CDFA by outlining the testing
procedures and test results. Once released by the State of
California, an application for federal quarantine release
is sent to USDA-APHIS, containing a copy of the letter
of approval from the State of California for release from
state quarantine. The distribution of citrus material released from quarantine is also a highly regulated and
carefully executed procedure that involves close interaction between CDFA, CCPP, and citrus nurserymen. After a variety is released from quarantine, it becomes
available to the commercial citrus industry or, in the
case of citrus genetic resources, it becomes part of one or
more of the three major collections of citrus genetic resources in California.
CONSERVATION OF CITRUS GENETIC
RESOURCES
IN GENERAL, PLANT GENETIC RESOURCES can be maintained as living plants in nurseries (ex situ) or in their
natural habitat (in situ), as ex situ seed collections, or as
ex situ collections of vegetative propagules or other tissues. The maintenance conditions for seed, vegetative
propagules, and tissues vary greatly according to the biology of the organism. Typically, seeds are kept at low temperatures with low humidity, although the use of cryopreservation for seed is increasing. Cryopreservation is
becoming a viable option for maintenance of vegetative
propagules and tissue cultures for many species. The
choice of an appropriate method is guided by the biology
of the species in question, the costs of the various viable
techniques, and a consideration of the genetic changes
that can occur over time in a collection. These latter
include mutation, chromosomal aberrations, genetic
shifts, and genetic damage (ROOS 1988). The goal of
genetic resource maintenance is to minimize genetic
change and maximize long-term viability.
While methods for the handling of citrus seeds in
genebanks have been considered (ELLIS et al. 1985), traditional seed storage techniques are seldom used. The
extended preservation of citrus genetic resources as seed
has certain genetic implications since the variable occurrence of nucellar embryony among species precludes
general recommendations for seed preservation (FROST
and SOOST 1968). Other problems with seed storage including loss of viability in low temperature have been
reported (ROBERTS 1975). Successful cryopreservation of
14
➌
CITRUS GENETIC RESOURCES IN CALIFORNIA
ONE OF THE LARGEST AND most diverse assemblages of
citrus genetic resources in the world is maintained in
California by a de facto conservation and utilization system that involves the federal government, the state government, the University of California, and the California citrus industry as represented by the Citrus Research
Board (CRB). The three primary components of this
system are the UC Citrus Variety Collection, the UC
Citrus Clonal Protection Program, and the National
Clonal Germplasm Repository for Citrus and Dates. The
federal government is represented by the USDA ARS
research units and individual scientists who work with
citrus, the USDA NPGS which maintains repositories of
citrus (see below for details on the NCGRCD), the
USDA National Research Initiative which awards research funds to competitive research proposals that have
included citrus research, and the USDA APHIS office
which establishes and enforces US plant import and export regulations. The state government is represented by
the California Dept. of Food and Agriculture which enforces for California the APHIS and California plant
material import regulations (see below for details on the
CCPP), administers the citrus marketing order under the
California Marketing Act, and administers pathogen
testing facilities. The University of California is represented by individual faculty scientists, the Division of
Agriculture and Natural Resources and the Agricultural
Experiment Station, the UC Riverside CNAS and several member departments, the CVC and CEBs (see below for details), and the UC Citrus Breeding Program.
The CRB is the panel of growers and researchers who
establish research priorities and direct funds raised by a
California marketing order on citrus production toward
those priorities. The goal of the CRB is to enhance the
production and marketing of highest quality citrus fruits
while being totally competitive in the domestic and international marketplace.
USDA researchers soon after the establishment of the
Citrus Experiment Station (CES) at the original site in
Riverside on the slopes of Mount Rubidoux. In June of
1917, Webber, the first director of the CES, guided the
installation of the Citrus Variety Collection on five acres
of land adjacent to the new site of the CES in what is
now the UC Riverside campus. The purposes of the
CVC are threefold: 1) to conserve and evaluate trueness-to-type of citrus and citrus relatives; 2) to provide a
resource of citrus genetic diversity for research; and 3) to
extend knowledge about citrus diversity.
Over the 87 years since its founding, the collection
has been supervised by 11 persons with some overlap in
tenure between 1982 and 1995 (Table 2). From 1912 to
1936, under the direction of Webber, budwood was freely
introduced into the collection from virtually all the citrus-growing regions of the world. Since 1910, when the
collection began, it has included a total of approximately
4,000 citrus accessions. These field plantings were located adjacent to what is now UC Riverside. Initially
most of the accessions were propagated on sour orange
rootstock. In 1951, under the direction of W.P. Bitters,
the collection was consolidated and repropagated onto
sweet orange rootstock due to the failure of certain genotypes on sour orange rootstock (Figure 16). These new
trees, as well as all new accessions on sweet orange rootstock added to the collection, were planted adjacent to
Table 2. Chronology of UCR Citrus Variety Collection
supervision.
Curator
CITRUS VARIETY COLLECTION (CVC)
The CVC, curated by T.L. Kahn, is the oldest component of the de facto California citrus conservation and
utilization system. It was initiated in 1910 (SOOST et al.
1977) by staff of the Citrus Experiment Station and
Date
R. Smith
1909–1911
Superintendent of Whittier and Rubidoux Labs
E. Coit
1911–1912
Superintendent of Whittier and Rubidoux Labs
H.J. Webber
1912–1936
Director of Citrus Experiment Station
L.D. Batchelor 1936–1946
Director of Citrus Experiment Station
W.P. Bitters
1946–1982
Professor of Horticulture
R.K. Soost
1982–1986
Professor of Genetics
E.M. Nauer
1982–1989
Specialist
M.L. Roose
1986–1995
Professor of Genetics
R.W. Scora
1986–1995
Professor of Botany
K.D. Bowman 1990–1992
T.L. Kahn
15
Title
Senior Museum Scientist
1995–present Senior Museum Scientist
the older trees. In the mid-1950s, WALLACE (1956) indexed certain trees in the CVC and found CTV present
in six trees (ROISTACHER 1981b). This presence of CTV
and a later indexing of 98 trees from the collection by
C.N. Roistacher and E.C. Calavan in 1963 precipitated
the repropagation of the collection again in 1966 onto
CTV-resistant, appropriate rootstocks including Troyer
citrange and Carrizo citrange (ROISTACHER 1981b).
During the mid- to late-1960s, seedling yellows, a severe
isolate of CTV probably began to move within the CVC
and into some of the field trees surrounding the CVC
(ROISTACHER 1982). Annual inspections by Bitters of
all the trees in the CVC determined that the number of
trees declining each year was increasing at an exponential rate even though they were on CTV-tolerant
rootstocks. This dramatic spread of seedling yellows between 1970 and 1980 was found to be due to a change in
the transmissibility of CTV (ROISTACHER 1981a).
In 1981, with support of the UC Riverside CNAS,
the CRB, and the State of California Employment Development Funds, a committee of UCR researchers appointed by the CNAS Dean initiated an intensive effort
to index all citrus trees at the Citrus Research Center
and remove those found positive for seedling yellows.
The collection was again consolidated and repropagated,
this time onto Carrizo citrange, C35, or another appropriate rootstock. These new trees were planted in 1983
into their current locations in Fields 12A, 12B, 18A, and
18B. Additional land was allocated in these fields for
expansion. Throughout the history of the CVC, new
accessions have been added to the collection and others
have been removed because they were very similar to
other types present. A few were lost due to tree death.
At the time of Bitters retirement in 1982, the CVC contained approximately 1,200 accessions. Since then some
400 accessions have been lost to attrition and selective
removal of apparent duplication.
Currently, the CVC occupies 22.3 acres on the
UCR campus, 2 acres at the UC South Coast Research
and Extension Center (SCREC) in Irvine, California,
and 2 acres at the UC Riverside Coachella Valley Agricultural Research Station (CVARS) in Thermal, California. The Citrus Variety Collection contains 865 accessions (identified in Appendix) within the genus Citrus and within 27 of the 33 related genera in the subfamily Aurantioideae of the Rutaceae. Approximately 670 of
the 865 accessions are within the subgenus Citrus and
encompass virtually all of the commercially important
and historic citrus varieties of the world (Table 3 and
Appendix). The majority (98%) of the accessions in the
CVC have been assigned PI numbers by the USDA
NPGS, either before or after inclusion in the CVC. About
580 of the those accessions (68%) exist only in the CVC.
Thus, the CVC is a key resource for the NPGS.
CITRUS EVALUATION BLOCKS (CEBS)
THERE ARE THREE COLLECTIONS of commercially important citrus varieties maintained in California, currently
under the direction of the curator of the CVC. These
Citrus Evaluation Blocks (CEBs, also known as Demonstration Blocks) are each collections of approximately
200 trees which include varieties that are also present in
the CVC. One is located at the UC Lindcove Research
and Extension Center (LREC), the second at SCREC,
and the third at CVARS. The CEBs serve as demonstration material for periodic field days that allow industry
representatives to evaluate new varieties. In addition,
along with the CVC, they serve as sources of fruit for
research conducted by the CVC curator to evaluate fruit
quality traits for trueness-to-type and commercial potential and for fruit displays as part of CVC outreach activities. Funding for fruit evaluations comes from annual
grants from the CRB. These grant funds cover the cost
of a Staff Research Associate position whose duties include assistance with management of the CVC to the
extent such activities are relevant to the objectives of
both units.
The CEBs are maintained by the staffs of their respective centers or station. The CEBs at LREC and
SCREC are projects subject to approval by the Research
Advisory Committee for each center. Approved projects
are allocated specific numbers of hours of care by staff at
that center.
W.P. Bitters, curator of the Citrus Variety
Collection from 1946 to 1982, holding Ponderosa lemons (CRC #0294), ca. 1950. During his tenure, the CVC
collection was greatly increased in number and diversity
of accessions. Photo courtesy of Special Collections,
Tomás Rivera Library, University of California, Riverside.
Figure 16.
16
use of infested budwood and mechanically on pruning
tools. In 1937, a voluntary program to provide growers
with a source of psorosis-free budwood produced under
CDFA regulations in cooperation with UC was initiated.
In 1939, quick decline (CTV), the devastating
bud-transmitted infection, was discovered in California.
Spread by certain aphids as well as by humans, this disease wiped out millions of trees in the 1930s and 1940s.
The danger of psorosis proved to be less than that of
CTV (and stubborn disease), and use of the psorosis-free
program declined.
By the early 1950s, it had become increasingly
clear that many conclusions drawn from earlier citrus
production experiments, especially rootstock trials and
those involving orange scions, were not valid due to undetermined and random viral infections. Experimental
plantings by J.W. Cameron and R.K. Soost of the Citrus
Experiment Station comparing nucellar strains and old
lines of commercial varieties generally showed that the
nucellar strains which were virus-free were superior in
vigor and yield.
It was becoming abundantly clear that a reliable
source of virus-free, true-to-type budwood would be of
great value to both researchers and growers. This led the
Citrus Research Advisory Committee (a forerunner of
today’s CRB, composed largely of prominent growers and
nurserymen) to request in 1957 that UC assume primary
responsibility for developing and maintaining healthy
citrus genetic resources, which were called ‘primary
foundation blocks’ and to provide this material under
regulations promulgated by CDFA.
This led to the establishment of the Citrus Variety
Improvement Program (CVIP) in 1958. This was initially a cooperative project between the UC Riverside
Depts. of Plant Pathology and Horticulture. The project
leaders were initially Professors E.C. Calavan and W.
Reuther. The CVIP was renamed the Citrus Clonal Protection Program in 1977 to indicate its functions more
precisely and to make clear that the program is not concerned with variety testing and breeding, except to provide and maintain healthy plants. In 1979, Calavan retired and was replaced by D.J. Gumpf. In 1992, the Dept.
of Plant Pathology took over sole responsibility for
CCPP (see website at http://www.ccpp.ucr.edu/
index.html).
The CCPP citrus collection, often referred to as
the Lindcove Foundation Block, is a field planting of
about 14.5 acres located at LREC in Tulare County in
the San Joaquin Valley of California. This block contains over 1,000 trees of about 200 different scion and
rootstock varieties of commercial importance. In 1996, a
special CRB subcommittee charged with seeking a way
to protect CCPP budwood sources recommended that
the collection should be maintained in a screenhouse
facility constructed to meet CDFA quarantine standards.
The facility was completed during the summer of 1998
(Figure 17). It is anticipated that the trees propagated for
CITRUS CLONAL PROTECTION PROGRAM
(CCPP)
THE CCPP, DIRECTED BY D.J. Gumpf, has a two-fold
mission: 1) it provides a safe mechanism for the introduction of citrus varieties from other citrus-growing areas of the world for research, variety improvement, or
commercial production and 2) it provides the California
citrus industry and researchers with a collection of important fruit and rootstock varieties which are tested and
maintained free of bud-transmitted diseases. The history
of the CCPP mirrors the development of our knowledge
of citrus virus and viroid diseases (NAUER et al. 1967,
REUTHER et al. 1972, CALAVAN et al. 1978, REUTHER
1981, GUMPF et al. 1997, BASH 1999, KRUEGER 1999b,
DUNLAP 2000). Before 1930, no viral diseases of citrus
had been identified. However, they existed and were
common in citrus production areas in California and
around the world. These viral diseases caused decreases
in tree vigor, yields, and fruit quality. One of the most
severe citrus virus diseases present in California was citrus psorosis virus, which greatly reduced the profitability
of citriculture. In 1932, H.S. Fawcett of the Citrus Experiment Station, the father of citrus pathology, showed that
psorosis was due to a virus and could be transmitted by the
Table 3. Type and number of accessions in the CVC.
Type
Mandarin
Number
107
Lemon, lemon-type
91
Sweet orange and hybrid
75
Pummelo (shaddock)
62
Navel orange
48
Trifoliate
48
Sour orange and hybrid
47
Trifoliate hybrid
43
Citron and hybrid
39
Lime, lime-type
32
Grapefruit
30
Citrus subgenus Papeda and hybrid
27
Pummelo hybrid
25
Tangelo
20
Valencia orange
18
Blood orange
17
Kumquat and hybrid
17
Tangor
14
Rangpur type
11
Miscellaneous Citrus species
10
Calamondin and hybrid
Grapefruit hybrid
Miscellaneous species, not genus Citrus
Total accessions
6
6
72
865
17
the new screenhouse facility will be mature enough to
start serving as a replacement for the Foundation Block
as the primary source of budwood in 2001. Newly imported varieties are added to the collection each year
after having been released from quarantine and fruited.
The trees are registered by the CDFA and are retested
for the presence of diseases at regular intervals. Any trees
testing positive are pulled from the block. Evaluations of
the trees and fruit produced on the trees are also done
regularly.
The Lindcove Foundation Block is currently the
primary source of budwood for the California citrus industry. Budwood from registered citrus trees in this collection is available for sale in limited quantities by UC
in accordance with CDFA regulations for citrus registration and certification. Potential purchasers are supplied
with a list of available cultivars, order forms, cutting
date, and deadline for submitting orders. Budwood is cut
three times each year. Individual nurseries or growers
may use the trees produced from buds to propagate additional trees for 18 months (24 if the trees are re-tested
during the first year). They may also register their own
trees and then use those trees to propagate additional
trees from them in a similar manner if CDFA requirements are met. Any citrus trees for commercial sale in
California must be certified by CDFA as having met certain requirements before sale. These regulations and the
CCPP have resulted in California having overall the
lowest disease incidence and highest fruit quality of any
citrus producing area in the world.
genetic diversity within Citrus, the 32 related Aurantioideae genera, and date palms and their relatives (Phoenix species) and to do research which supports these objectives (WILLIAMS 1990, 1992a,b, KRUEGER 1999a).
The NCGRCD is a part of the USDA NPGS and is a
cooperative effort between USDA-ARS and the UC
Agricultural Experiment Station.
The NPGS emerged in 1974 as an umbrella system
which incorporated genetic resource-related activities
which had previously been parts of a wide range of agencies within and outside of ARS. Components incorporated into the NPGS included New Crops Research
Branch, the Regional Plant Introduction Stations, the
Plant Introduction Office, and other entities. The NPGS
was established with the goal of collecting, evaluating,
maintaining, and preserving plant genetic resources
(SHANDS et al. 1988, WHITE et al. 1991, SHANDS 1995).
Guidelines were developed for this system incorporating
ideas suggested by RAVEN (1976), NATIONAL RESEARCH
COUNCIL (1978), and others culminating in an operational program for the United States (SHANDS et al. 1988,
NATIONAL RESEARCH COUNCIL 1991, SHANDS 1995).
The NCGRCD was established in 1987 on the
UCR campus (see website at http://www.ars-grin.gov/
riv/). This location was chosen to take advantage of the
resources available at the Citrus Experiment Station,
particularly the CCPP and the CVC. D.J. Gumpf of the
CCPP was largely responsible for the conceptualization
and specifications which resulted in the design of the
facilities, and served as the University’s chief contact
and liaison with ARS. The first NCGRCD curator was
T.E. Williams, who served from 1987 through 1993. He
was succeeded by R.R. Krueger in 1994.
One of the NCGRCD’s primary purposes is to exchange genetic resources with scientists all over the
world. The stated mission of the NPGS is to facilitate
and encourage the free exchange of genetic resources.
Consequently, the NCGRCD distributes materials free
of charge to qualified scientists, as do other units of the
NPGS. Exchange of citrus genetic resources is highly
regulated. Most citrus-producing countries have restrictions on the introduction of new citrus materials to prevent the concurrent introduction of new pathogens or
strains of pathogens. Most countries will accept only
pathogen-free citrus budwood. Therefore, the NCGRCD
maintains a screenhouse collection of over 700 virus-free
trees which represent nearly 350 accessions. These are
the primary source of budwood for distribution. Approximately 55 accessions of citrus relatives are also maintained
in greenhouse or screenhouse chambers (Figure 18).
There are several ways that the NCGRCD obtains
new virus-free genetic resources. The CCPP was designated to be the primary vehicle for introduction and
quarantine of new accessions which are received as
clonal (vegetative) materials from sources outside California. The NCGRCD also receives material directly as
seed after inspection in Beltsville, Maryland. Material
NATIONAL CLONAL GERMPLASM
REPOSITORY FOR CITRUS AND DATES
(NCGRCD)
THE MISSION OF THE NCGRCD, directed by R.R.
Krueger, is to acquire, preserve, distribute, and evaluate
Figure 17. Budwood source trees for the Citrus Clonal
Protection Program in a screenhouse-protected planting
at the Lindcove Research and Extension Center. Photo
credit: David J. Gumpf.
18
received as seed is generally undeveloped or semi-wild
material, primarily citrus relatives, which usually come
true-to-type from seed. Finally, to increase the genetic
diversity of its virus-free collection, the NCGRCD is
introducing accessions from the CVC into the screenhouse collection. This is done by an internal quarantine
process similar to the one outlined above for the introduction of foreign materials. This allows the acquisition
of noncommercial types which are difficult to obtain and
have a low priority for processing by CCPP. NCGRCD
has submitted applications to APHIS to be permitted as
a quarantine program. If approved, this would alleviate
some of the pressure on the CCPP quarantine program
and also increase the capacity to acquire new germplasm.
NCGRCD collaborates and interacts formally and
informally with CCPP, CVC, and other researchers on a
regular basis. Collaborative projects have included horticultural and molecular characterization of accessions in
the CVC, development of improved anti-serum for increased sensitivity of ELISA testing, and varietal trials.
This continues a productive association between the
USDA and the Citrus Experiment Station that started
with the activities of G.H. Powell and A.D. Shamel in
the early 1900s (LAWTON and WEATHERS 1989).
INTERRELATIONSHIPS AMONG CVC,
CEBS, CCPP, AND NCGRCD
THE UNIQUE WORKING RELATIONSHIPS among the
CVC, CCPP, CEBs, and NCGRCD have evolved to produce a comprehensive citrus genetic resource conservation and utilization system for the State of California.
Their individual goals are very closely interrelated but
are not duplicative. Figure 19 illustrates the flow of genetic resources into and out of the system and among
these four units and the UC Riverside Citrus Breeding
Program which maintains some accessions used for
breeding that are not in any of the other collections.
New introductions that are to be incorporated into any
one of the collections and which are imported as budwood must be introduced to the California system by
way of the CCPP to prevent the inadvertent introduction of pathogens or pests not found in California. CCPP
quarantines incoming clonal material and supplies budwood to the commercial industry in California. New cultivars entering California that appear to have direct
commercial value are kept in the CCPP collection for
evaluation and possible distribution. The same materials
may be added to the CVC and NCGRCD collections
depending on their specific needs and requests. Materials
that are solely for germplasm enhancement are not kept
by the CCPP, but are moved directly after quarantine to
the CVC and NCGRCD facilities for maintenance. The
NCGRCD distributes clonal materials to the national
and international citrus research community. The CVC,
which maintains the largest number of accessions and
the largest amount of genetic diversity, is used as a resource for a myriad of research projects, extension activities, evaluation and characterization of accessions, as
well as a source of materials for indexing/clean-up and
nonclonal materials, and serves as a backup to the virusfree collections.
The CVC collection is a field planting exposed to
natural infections of a number of diseases, notably CTV,
which is pervasive in the area. Trees in the CVC are not
registered by CDFA and so cannot serve as a budwood
source for trees for commercial or experimental purposes
or for national or international distribution. However, a
permit was granted by the CDFA in 1996 to allow repropagation of citrus trees in the CVC that need to be retained in the collection from untested source trees in the
CVC since many of the accessions present in the collection are found nowhere else in North America. Seed and
pollen from CVC accessions can be distributed to researchers outside of California and the US, since seed
and pollen generally do not transmit diseases critical to
citrus production.
The CVC also has been a source for accessions
maintained in the NCGRCD virus-free genetic resource
collection. The CVC serves as a source of seeds, pollen,
flowers, etc. for distribution by NCGRCD and as a field
planting for NCGRCD accession evaluation and charac-
Seedlings of indicator plants for indexing,
growing in cool-temperature chamber of NCGRCD
greenhouse facilities. Photo credit: Polly M. Balance.
Figure 18.
19
Citrus clonal
material from
outside California
and the US
Citrus seed and pollen
from outside California
and the US
Imported into California directly to
the CCPP under US federal and
California regulations
Imported into California directly to the
CVC or the NCGRCD under US federal
and California regulations.
Citrus Clonal
Protection Program
(CCPP)
UC Riverside
Citrus Breeding
Program
Movement of citrus
genetic resources
within California
Citrus
Evaluation
Blocks (CEBs)
National Clonal Germplasm
Repository for Citrus and
Dates (NCGRCD)
Citrus Variety
Collection
(CVC)
Citrus genetic resources move to California citrus nurseries as virus-free budwood from the CCPP and
to national and international citrus researchers as virus-free budwood from the NCGRCD and as
seed and pollen from the CVC and NCGRCD.
Commercial citrus
nurseries
California
citrus growers
National and
international citrus
researchers
Consumers
Movement of citrus genetic resources into, within, and out of the Californa system for conservation and
utilization of citrus genetic resources.
Figure 19.
20
terization activities. Materials obtained by the NCGRCD
via exchange for incorporation into the virus-free collection need to be established in the field. Thus, both a virus-free collection maintained under screen and a field
collection will continue to be necessary for NCGRCD in
the future. Through the NCGRCD, the CVC has contributed to studies of cryopreservation of citrus seeds,
pollen, and vegetative tissue; citrus taxonomy and genetics; and blight-associated proteins. Thus, the CVC plays
an important role in fulfilling the NCGRCD mission
and in contributing to citrus research world-wide.
The NCGRCD screenhouse collection is a protected and tested collection that may serve directly as a
source for filling requests for budwood. NCGRCD distributes materials to scientists, scientific organizations,
and governmental agencies throughout the world but
does not distribute directly to citrus growers except under unusual circumstances. The long-range goal of the
NCGRCD is increasing the number of disease-free accessions of unimproved, wild-type genetic resources,
breeding lines, and other nonelite material that it maintains, rather than concentrating on varieties of potential
commercial importance, leaving that to the CCPP.
The small size of the NCGRCD trees and limited
amount of screenhouse space also makes distribution of
commercial quantities of budwood infeasible. The CCPP,
on the other hand, is a field planting of mature trees
which are capable of supplying commercial amounts of
budwood. The number of trees planted in the Foundation Block of the CCPP can also be increased readily if
demand increases.
21
22
➍
US CITRUS GENETIC RESOURCES OUTSIDE CALIFORNIA
WHILE CALIFORNIA IS HOME to the largest and most diverse collection of citrus genetic resources in the US,
there are several other collections of interest outside of
California. None of the collections described below approach the CVC in size or breadth of genetic diversity,
and none of them can supply virus-free budwood, as can
CCPP and NCGRCD. Additionally, the majority of the
collections are more vulnerable to pests, diseases, and
adverse weather conditions such as freezes and hurricanes than are the California collections.
The USDA-ARS National Germplasm Repository–Miami, located at the Subtropical Horticulture
Research Laboratory, maintains a limited number of accessions in the Aurantioideae. This collection is notable
for the age and size of some of accessions of genera related to Citrus. There is also a small collection of Citrus
and other Aurantioideae genetic resources maintained
at the USDA-ARS Tropical Horticulture Laboratory in
Mayagüez, Puerto Rico. Accessions maintained here are
not available as virus-free materials.
The Florida State Dept. of Plant Industry maintains the Florida Citrus Arboretum at Winterhaven.
This is a well-maintained and attractive collection of
over 250 accessions, and includes a good representation
of citrus relatives. However, most accessions are represented by only one tree; virus-free materials are not available; and the area is vulnerable to freezes and hurricanes.
Breeding collections are maintained by the citrus
breeders at the University of Florida Citrus Research
and Education Center in Lake Alfred. These collections
contain some unique and valuable accessions such as
recently described introduced species and polyploid accessions. However these collections are not generally
accessible, cannot supply virus-free material, and are not
always available for distribution or exchange. There is
also a small collection of Citrus and other Aurantioideae genetic resources maintained without regard to
virus status at the University of Florida Tropical Research and Education Center in Homestead.
Florida. The largest collection of citrus genetic resources
in Florida is the USDA-ARS A.H. Whitmore Foundation Farm Variety Collection (WFFVC). The WFFVC is
administered by the USDA-ARS-USHRL. The collection was started in the late 1950s by consolidation of
several other USDA collections (primarily in Florida,
but also including Indio, California) to support citrus
breeding programs at USHRL. The WFFVC, on its
Groveland, Florida site, served as a field facility for
USHRL breeders before being incorporated into the
NPGS in 1987 as a repository. It was decommissioned in
1992 and reverted to its previous status of a breeding collection. There were approximately 250 accessions maintained at the WFFVC Groveland site, about half of
which are not duplicated in any California collection.
Yet the WFFVC has few representatives of genera related to Citrus and virus-free materials are unavailable.
The USHRL moved from Orlando to Fort Pierce,
Florida in 1999. Accessions of the WFFVC testing negative or having only mild strains of CTV will be
repropagated at Fort Pierce, but accessions testing positive for severe strains of CTV will not be. There are no
plans for virus elimination via thermal therapy or shoottip grafting at this point. Therefore, virus-free materials
will still not be available from this collection. The Fort
Pierce WFFVC collection is thus initially smaller than
the original Groveland WFFVC collection, but additional accessions will be added over time. The Fort
Pierce site should be less subject to destructive freezes
than the original Groveland site, but it is also subject to
many endemic citrus diseases that may threaten the
phytosanitory status of many accessions.
Texas. The Texas A&M University, Kingsville Citrus
Center (TAMUK) at Weslaco has a collection of over
200 accessions. Some of these accessions are not present
in California, but overall this collection does not have
the diversity present in California. There are few citrus
relatives in this collection.
The Rio Farms Citrus Variety Collection is located approximately 10 miles from Weslaco in Monte
Alto. This collection was originally established by the
USDA in the 1960s and was taken over by Rio Farms, a
private organization, when the USDA discontinued citrus research in Texas in the 1970s. There are over 100
accessions in the Rio Farms collection, some of which
are not present in the California collections. This col23
lection has suffered more than the TAMUK collection
from freezes, and was recently damaged by gummosis.
Rio Farms is less interested in citrus production than in
the past, and this collection will probably be lost. Some
of the more valuable accessions are in the process of being incorporated into the CVC, CCPP, and NCGRCD
collections.
24
➎
INTERNATIONAL CITRUS GENETIC RESOURCES
THE CENTER OF ORIGIN and diversity of citrus is in
southeast Asia. Consequently, this is where the greatest
amount and diversity of citrus genetic resources may be
expected to be found, particularly in situ (REUTHER
1977, IBPGR 1982). Assessment of the genetic vulnerability of any species requires knowledge of the extent
and distribution of genetic diversity. Unfortunately, information on natural and semi-natural citrus genetic resources is limited. The information that is available is
often simply a catalog of plants present in an area, with
little more than names and phenotypic descriptions. Often even information on the frequency of occurrence is
lacking. More detailed characterization and evaluation
data are needed to assess adequately the actual amount
of genetic diversity present. These data should include
both descriptive information and molecular level genetic
analyses.
The report, The State of the World’s Plant Genetic Resources for Food and Agriculture (accessible at
http://web.icppgr.fao.org/wrlmap_e.htm), was prepared for the International Technical Conferences on
Plant Genetic Resources in Leipzig Germany in 1996. In
this report the number of citrus accessions worldwide
were listed at 6,000 which included a mixture of wild
species, old cultivars, and advanced cultivars and breeding lines. In an effort to better understand the nature of
these collections and promote conservation of citrus and
related genera, a global network on citrus genetic resources conservation and utilization was formally constituted under the aegis of the FAO in 1997. The Global
Citrus Germplasm Network (GCGN) will function on a
voluntary basis and will involve national institutions
and existing regional and inter-regional citrus networks.
The purpose of the network is to link different initiatives
in different parts of the world that deal with genetic resources exploration, conservation, and utilization. The
GCGN is chaired by a General Coordinator and guided
by Coordinating Board. Within the GCGN four working
groups were defined to conduct the scientific and technical work of the global network focused on genetic resource characterization; establishment of a global computerized citrus genetic resource information system;
conservation strategies; and utilization of citrus genetic
resources.
In the southern and southeastern Asian countries
to which Citrus and related genera are indigenous, development and consequent habitat loss is occurring due to
deforestation, population pressure, fire, and hydroelectric, agricultural, and other development pressures. Habitat loss results in a loss of genetic diversity. Efforts are
being made at habitat preservation in these areas, however, ex situ preservation of genetic resources has become
imperative due to the rapidity of habitat loss. Ex situ collections also make genetic resources more readily available to users and facilitate characterization and evaluation. What follows are brief descriptions of the status of
in situ and ex situ collections of citrus and citrus relatives
in selected countries and regions.
China. Southern China is one of the centers of diversity
for Citrus and related genera, and a wide range of genetic
diversity is apparently still present in situ (GMITTER and
HU 1990, ZHENG 1995, DENG et al. 1997, CHEN 1997).
However, some, although not all, areas are threatened
with habitat degradation or lack of proper management
that could result in decreases in genetic diversity. Chinese governmental surveys during the 1970s uncovered a
number of putative new species, including C. honghensis,
C. mangshanensis, C. daoxianensis, and Poncirus polyandra. These putative species are mostly unknown outside
of China and some may be endemic. There is use of indigenous genetic resources in China, and some attempts
at in situ preservation have been made. However, conservation of citrus genetic resources in China consists
mostly of ex situ collections at present. Beginning in the
early 1960s, a National Citrus Germplasm Repository
was established at Chongqing, Sichuan province, and
regional citrus genetic resources repositories were established in Huangyan, Zhejiang province; Guiling, Guangxi province; Zhangsa, Hunan province; and Guangzhou,
Guangdong province. As of 1996, the National Citrus
Germplasm Repository had 1,041 accessions, while the
Huangyan, Guiling, Zhangsa, and Guangzhou regional
repositories had 128, 216, 40, and 140 accessions, respectively. These current numbers represent substantial reductions in accessions since the repositories were established. The reductions were due to such factors as lack of
funds, disease, and freezing weather. The exact contents
25
of these collections is unknown, but a high percentage is
indigenous, and undoubtedly represents a substantial
amount of diversity not present in collections elsewhere
in the world. Some of the accessions, indigenous and
otherwise, consist of advanced lines or selections. The
collections in the repositories have had received only a
limited amount of characterization and evaluation.
Although not as large as some collections, these Southeast Asian collections have notable genetic diversity,
particularly in the pummelos and some of the related
non-Citrus genera, and appear to be fairly well maintained and curated.
Asia’s largest collections, outside of the centers of
origin discussed above, are in Japan (OMURA 1997). Citrus entered Japan in ancient times and some types became semi-naturalized. The federal Fruit Tree Research
Station in Tsukuba has a large collection maintaining a
number of citrus relatives. This station has been active
in collecting in Nepal (1983–1985) and Vietnam (1996)
in IPGRI-coordinated cooperative programs. Accessions
collected from these ventures are maintained in Japan.
The accessions at Tsukuba and in various other, smaller
collections total approximately 1,200 (OMURA 1997).
India. Northeast India is a center of origin and diversity
for Citrus and related genera. Genetic diversity of indigenous Citrus species in this region is gradually eroding
(RAI et al. 1997) and the area is experiencing civil unrest, making evaluation of genetic diversity and plant
exploration difficult. There are apparently a few stands
of wild citrus in these areas, but many of the wild populations consist of dooryard plantings. A long history of
cultivation and selection have produced many genotypes
and landraces, which are difficult to distinguish from
wild citrus populations. Still, a wide range of genetic diversity undoubtedly exists in these areas (SINGH 1981,
CHADHA 1995, SINGH and UMA 1995, RAI et al. 1997).
There is an in situ gene sanctuary for citrus in the Garo
Hills in the northeast of the state of Assam, which is a
field genebank with 627 accessions (SINGH 1981). Other
regions of diversity include the central and northwest
Himalayas, Maharashtra, and the southern peninsula. Ex
situ conservation of citrus genetic resources began in the
1950s in India, but the number of accessions maintained
has declined due to lack of maintenance and disease. Ex
situ collections consist of 451 or 521 accessions (depending on the source of the estimate) at eight sites (Chetalli, Bangalore, Rahuri, Tirupati, Abohar, Bhatinda, Yercaud, and Delhi). The ex situ collections in India are
mostly of rootstock varieties and a few local cultivars,
with not much diversity represented. There is a plan to
concentrate the various collections at the National Research Centre for Citrus in Nagpur. However, as of January 1996, there were only a small number of accessions
planted at Nagpur.
Australia. Indigenous citrus relatives include taxa in the
genera Eremocitrus and Microcitrus, for which Australia is
the center of origin. These taxa probably served as aboriginal foods. Organized ex situ citrus genetic resource
maintenance and utilization is conducted today by state
government departments of agriculture and primary industries, the federal Commonwealth Scientific and Industrial Research Organization (CSIRO), and various
arboreta, botanical gardens, and university plant collections (SYKES 1997). In total, these collections include
about 500 accessions and are rich in diversity of cultivated types. Most accessions are backed up by duplication in different sites. Acquisition of new material by
budwood is limited due to quarantine concerns, but seed
importation and subsequent characterization and evaluation of Citrus relatives from other Southeast Asian countries and materials with rootstock potential has been an
ongoing activity, especially of CSIRO as part of a program of genetic resources enhancement.
Elsewhere. Outside of the centers of origin and diversity,
collections consist mostly of advanced lines and commercial varieties in countries with citrus production and
citrus breeding programs. ROUSE (1988) and BETTENCOURT et al. (1992) have summarized the world citrus
collection situation identifying major and minor ex situ
citrus collections. Large ex situ collections of citrus are
found in Argentina, Brazil, Corsica, Morocco, New Zealand, South Africa, Spain, and Turkey. Although the
number of accessions reported for some of these collections exceeds the number maintained by the CVC in
California, the amount of genetic diversity present is
generally less than in the CVC. For example, some of
the larger collections contain many selections of the
same variety, and so the genetic diversity is less than
might be expected from the number of accessions. Representatives of genera related to Citrus are particularly
lacking in most of these collections. On the other hand,
some of the smaller collections worldwide may not offer
a large number of varieties or much diversity, but may be
Other Southeast Asian countries. The area is rich in
indigenous Aurantioideae genetic resources, with chance
seedlings, semi-wild, and wild types. There are three collections in Malaysia (JONES 1991, SAAMIN and KO
1996), the main one being the Malaysia Botanical Garden (over 100 accessions), three in Indonesia (498 accessions), three in Thailand (585 accessions), and two in
the Philippines (107 accessions). There are also some in
situ conservation efforts. In the period 1983 to 1988, the
International Plant Genetic Resources Institute (IPGRI,
then the International Board for Plant Genetic Resources) coordinated four collecting missions to Thailand,
Malaysia, Indonesia, and Brunei resulting in the addition
of 391 new accessions (these are maintained in Japan,
the organizer of the missions). In 1986, IPGRI invited
Malaysia to accept responsibility for maintaining a field
collection of Southeast Asian species of Aurantioideae.
26
tended for the preservation of diverse species encompassing the genus Citrus as well as related genera exist in
only a few places in the world besides the CVC. Most
collections in other countries consist of field plantings,
and, with a few notable exceptions, virus-free budwood
is not available. The Citrus Germplasm Bank, Instituto
Valenciano de Investigaciones Agrarias in Valencia,
Spain is one of those exceptions and virus-free material
is available. Spain’s quarantine and certification programs are among the world’s best and most respected
(NAVARRO et al. 1988).
important for indigenous local variation in Citrus or for
endemic species. For instance, BETTENCOURT et al.
(1992) list Cameroon as having some indigenous
Citropsis species in their collection.
These collections vary as to the purposes they
serve. Most of the collections are located in countries
where citrus is not native, so they serve a multiplicity of
functions including limited genetic resources maintenance for crop enhancement and breeding and as
mother trees for the production of trees for a commercial
fruit industry. Large genetic resources collections in-
27
28
➏
ANALYSIS AND RECOMMENDATIONS IN SUPPORT OF CITRUS
GENETIC RESOURCES IN CALIFORNIA
Recommendation 1. No changes in the management structure of the CVC, the CCPP, or the NCGRCD are advocated. The continued close collaboration among the three
units is essential to the functioning of a citrus genetic resources conservation and utilization system for California.
THE CALIFORNIA CITRUS GENETIC
RESOURCES CONSERVATION AND
UTILIZATION SYSTEM
THE THREE PRIMARY COMPONENTS of the California system for maintaining and providing citrus genetic resources are the UC Citrus Variety Collection (CVC), the
UC Citrus Clonal Protection Program (CCPP), and the
National Clonal Germplasm Repository for Citrus and
Dates (NCGRCD). Each unit has a different history and
origin and the interrelationships among them have been
ad hoc. However, this situation has been functioning
well in service to the California citrus industry and citrus
researchers providing one of the largest and most diverse
assemblages of citrus genetic resources in the world.
Each of these three components has distinctly different organizational and administrative structures. The
CCPP is managed within the Department of Plant Pathology, while the CVC is managed within the Department of Botany and Plant Sciences, both within College
of Natural and Agricultural Sciences, UC Riverside. The
NCGRCD is managed for the NPGS by ARS staff reporting to the Pacific West Area office in Albany, California. Each unit may also have responsibilities in addition to the focus on genetic resources for California. For
example, academic priorities may redirect staff activities
for the two UC units. For the NCGRCD, its role in the
NPGS gives it national responsibilities and its mission also
includes another crop entirely—dates (Phoenix spp.).
While this document focuses primarily on live tree
conservation, it is becoming increasingly apparent that
citrus genetic resource management will need to expand
to include such resources as DNA libraries (both cDNA
and genomic DNA libraries), molecular probes, and
clones. It is not clear what unit in the California citrus
genetic resources system should initiate such collections,
but concern for such material is put forward here as a
recommendation.
The remainder of this chapter consists of an analysis for the CVC of the operational aspects of a genetic
resources operation and recommendations to enhance
and facilitate the continued success of the CVC in conserving citrus genetic resources for California.
Recommendation 2. The establishment of a California
Citrus Genetic Resources Advisory Committee
(CACGRAC) is recommended. This committee, composed
of research and extension workers, agency and University
administrators, growers, processors, marketers, consumers,
and others, will provide guidance to the staffs of the units that
comprise the California citrus genetic resources conservation
and utilization system to assure the acquisition of critical genetic resources and their long-term conservation and efficient
distribution.
Recommendation 3. The dependence of the NCGRCD on
the CVC for seed and field evaluation facilities should be officially recognized by the parent organization of each unit and
enhanced by a long-term commitment of support for the
CVC by the USDA NPGS.
Recommendation 4. Citrus genetic resource management
for California should expand to include resources such as
DNA libraries, probes, and clones. The appropriate unit and
adequate funding for the effort should be topics for consideration by the proposed California Citrus Genetic Resources
Advisory Committee. (Rec. 2 above).
THE CITRUS VARIETY COLLECTION
Activities
Acquisition. With no budget directed to this activity,
the addition of new accessions into the CVC is slow, depending upon research collaborations and serendipity.
There is recognition that acquisition should be a continuing activity, but there is no strategy in place for
evaluating the collection for underrepresented taxa,
genotypes, or geographic origins and actively seeking out
acquisitions. Even with some new accessions, the collection has grown smaller overall since its peak size of some
1,200 accessions in the early 1980s. This was primarily
due to attrition loss and selective removal of duplicates.
29
Recommendation 5. There should be continued and enhanced linkages with other national and international citrus
genetic resources collections.
phasized and pesticide usage kept to a minimum is a
long-term goal for the CVC, but progress is slow with
available funding.
Care for the trees in the 22.3 acre portion of the
CVC located at UCR is done by UCR Agricultural Operations personnel. The Agricultural Operations office
estimated the annual costs of its services for the CVC at
about $24,000. In addition during 1997–98, the staff of
the CVC obtained voluntary assistance from the Riverside County UC Cooperative Extension Master Gardeners in fruit reduction and pruning in the CVC. The estimated annual costs for these services without volunteer
assistance are $2,000 for pruning and $7,000 for fruit
reduction.
Care for the three CEBs and the collection of citrus relatives at SCREC is conducted by the staff at the
respective location. The number of hours needed to
maintain the trees and funds for their care at LREC and
SCREC are allocated by the Reseach Advisory Committees for each center. If the amount of care needed exceeds the amount of funds allocated, the excess cost is
charged to the CVC budget and funded projects associated with the CEBs.
Recommendation 6. Acquisition of new accessions, both
from within and outside California and of wild or naturally
occurring citrus relatives from their native habitats, is an important function for the CVC. Acquisitions should be guided
by a plan developed with assistance of the recommended advisory committee. Every effort should be made to acquire accessions for the CVC that are not currently available in California, taking full advantage of the California system that
allows importation of citrus genetic resources.
Documentation and database management. Each accession in the CVC generates data beginning with the passport data from the acquisition stage and ultimately including evaluation and characterization data accumulated as the accession is utilized. Maps and records of the
varieties present in the CEBs are maintained separately
from those of the accessions in the CVC. Prior to 1996,
records for the CVC were kept solely on 4 × 6-inch
cards. This procedure, maintaining a card for each accession, had been followed since the inception of the collection. In 1996, the information was transferred to a
computer database which permits easy updating of information and manipulation of the data for record keeping
(see Appendix). From 1996 to 1998, the CVC received
funding to update and expand its database and to develop links between the CVC and other databases increasing its usefulness to a wider range of researchers and
other interested parties. CVC accessions are also entered
in the USDA Genetic Resources Information Network
(GRIN) database (http://www.ars-grin.gov).
Rootstock status. When an accession is represented by
two trees (which is the case with most of the 865 accessions), two different rootstocks are used: one instance of
the accession would be on Carrizo citrange and the other
would be on C-35 citrange or another appropriate rootstock.
Irrigation. All trees in the CVC will be on a low volume
micro-sprinkler irrigation system such as is used by most
commercial citrus operations in California. Although
furrow irrigation provides adequate water (Figure 20), a
low-volume irrigation system offers many advantages: it
can save water and labor and allows fertilizers to be injected into the irrigation water when needed (STATEWIDE INTEGRATED PEST MANAGEMENT PROJECT 1991).
During 1998, one-third of the trees were converted to
such a system with financial support ($1,000) from CVC
funds in combination with a donation of available irrigation supplies and 285 hours of labor from UCR Agricultural Operations. The remaining two-thirds of the trees
are being converted with funds from a one-year grant
awarded in 2000 from the California Citrus Nursery Advisory Board.
Recommendation 7. The CVC database should be enhanced to include digital representations of important accession characteristics such as photographs of flower, leaf, and
fruit morphology, gels of biochemical and molecular genetic
analyses, and disease susceptibility or resistance symptoms.
Recommendation 8. There should be continued exchange
of information between the CVC and the USDA NPGS
GRIN databases.
Maintenance. The CVC maintains at least two trees per
accession for each of the 865 accessions currently in the
collection. The cultural practices required for the trees
include: irrigation, fertilizer applications, pest control,
weed control, pruning, fruit reduction, tree care, and
frost control. Minimizing pesticide use in the collection
orchards is essential for a collection that is often used by
researchers and visitors who may consume fruit samples
as a means of evaluating new and commercial cultivars
in the collection. Full implementation of integrated pest
management techniques by which release and maintenance of beneficial insects and predatory snails is em-
Recommendation 9. Full implementation of integrated pest
management techniques should be deployed in the CVC
plantings which, along with the full installation of the lowvolume irrigation system, would not only increase the efficiency of tree cultivation in the CVC, but would also enhance the unit as a showcase for California citrus.
30
Recommendation 10. The CVC needs to monitor information about citrus pathogens and keep in contact with citrus
specialists to anticipate disease threats to the collection.
representatives in advance of crisis-driven needs. Information for such characteristics is available in the literature for some of the CVC accessions, but further confirmation and characterization is increasingly necessary as
the range of techniques available to manipulate citrus
genetic resources increases.
The CVC serves as a resource for a myriad of research projects from scion and rootstock breeding for the
improvement of commercial varieties to the study of the
biological activities of citrus limonoids as anticancer
agents. Since 1997, 38 different projects have used CVC
materials, conducted by researchers at UC Riverside,
University of Arizona, Auburn University, University of
Florida, and USDA (Table 4). These projects covered a
range of topics: eight focused on scion and rootstock
breeding; 11 involved characterization of accessions for
commercially important traits such as disease resistance/
susceptibility and anticarcinogenic activity of citrus
limonoids; eight focused on isolating, mapping, and
transferring specific genes; four investigated the phylogeny and genetic diversity of citrus and citrus relatives;
two focused on cryopreservation; and five others involved research on pathogens of citrus, stress reactions,
or biochemistry of citrus extracts. The CVC staff directly
conducts research: two projects utilize accessions in the
CVC and the CEBs and the third is a mandarin variety
trial for the California desert, being conducted at CVARS.
Evaluation, characterization, and research. Evaluation
and characterization of CVC accessions is driven by objectives of externally funded research projects, often crisis driven. For example, evaluation of a portion of the
accessions for resistance to a specific disease could only
be accomplished in conjunction with a funded project to
work on that characteristic. Several of the research
projects described below are of this nature. Ideally, maintenance of a field collection needs to be coupled with
periodic evaluations of accessions for trueness-to-type
and characterizations for traits of value to researchers
and the citrus industry. Information on traits such as disease resistance/susceptibility, monoembryonic or polyembryonic seed production, pollen viability, self-compatibility, cross-incompatibility relationships, and rootstock-scion incompatibilities would be valuable for researchers, citrus growers, nurserymen and other industry
Recommendation 11. Users of the CVC should be encouraged to contribute to the maintenance of its collections.
Dissemination of information. The CVC is used extensively as a resource for educational extension activities
on the UC Riverside campus. California citrus growers,
nurserymen, and other industry representatives as well as
students from University of California and California
State University campuses visit the CVC each year to
evaluate potential commercial citrus varieties and learn
about citrus diversity. Many visitors from other states
and countries also tour the CVC since it is internationally renowned for citrus diversity. In addition to tours of
the CVC, since 1995, the staff has provided numerous
fruit displays and oral presentations to disseminate information on the performance of various citrus cultivars
and on citrus diversity.
From March 1999 to March 2000, the staff conducted twenty-five off-campus presentations including
four oral presentations to growers groups sponsored by
the Citrus Research Board, fruit displays for the Sunkist
Annual Meeting, the Tulare Farm Equipment Show, and
the for members of the US Congress and their aides in
Washington DC, field days at the three evaluation
blocks, and poster presentations at the Orange Show and
a two-day citrus diversity fruit display and poster session
at the Riverside Orange Blossom Festival where over
150,000 visitors to the Festival had the opportunity to
ask questions about and taste 30 different types of citrus
Headstand of furrow irrigation system once
used at the CVC, now replaced by the more efficient low
volume micro-sprinkler irrigation system, typical of most
commercial citrus operations. Photo credit: Michael J.
Elderman.
Figure 20.
31
Table 4.
Research projects utilizing accessions in the CVC (1997–2001).
Project description
Investigator
Institution/Department
Citrus variety evaluation for trueness-to-type and commercial potential.
T.L. Kahn, M.L. Roose
UCR Botany & Plant Sciences
Preliminary evaluation of parthenocarpy of new Clementine mandarin selections.
T.L. Kahn
Evaluation of new citrus selections–Sensory evaluation.
T.L. Kahn, M.L. Arpaia
Characterization of lime accessions
T.L. Kahn, M. Harris
Development of a detailed genetic map of citrus, including genes for resistance to citrus tristeza
virus, Phytophthora tolerance, apomixis, and fruit acidity.
M.L. Roose
Identification and cloning of a gene that controls citric acid accumulation in citrus fruit.
M.L. Roose
Inheritance and molecular genetic analysis of apomixis (nucellar embryony) in citrus.
M.L. Roose
Positional cloning of a trifoliate orange gene that confers immunity to citrus tristeza virus.
M.L. Roose
Use of molecular markers including RFLPs, RAPDs, ISSRs, and SSRs to understand phylogeny
and genetic diversity of citrus. Current work emphasizes lemons.
M.L. Roose
A project initiated to identify a core collection of about 100 accessions, which represent a
large proportion of the genetic diversity present in citrus. First phase will involve screening the
entire germplasm collection for SSR (single sequence repeat or microsatellite) markers.
M.L. Roose;
R.R. Krueger
UCR Botany & Plant Sciences;
USDA-ARS-NCGRCD. Riverside CA
Development of improved methods for genetic transformation of citrus and their application
to develop cultivars resistant to citrus tristeza virus.
M.L. Roose
Development of new, early maturing grapefruit cultivars and seedless mandarins by hybridization
and mutation breeding.
M.L. Roose
Development of new rootstock cultivars which reduce tree size, have improved disease
resistance, broader soil adaptation, and desirable effects on fruit quality.
M.L. Roose
Development of citrus cultivars with enhanced characters using the tools of molecular genetics.
Current efforts focus on reducing seed set and enhancing tolerance to pathogens and pests.
L. Walling
Regulation of flowering in sweet oranges
L. Pillitteri, C. Lovatt,
L. Walling
Explorations of stress proteins as indicators of freeze damage in oranges.
T.J. Close
Screening of citrus lines for susceptibility to Agrobacterium rhizogenes.
O. Becker
UCR Nematology
Detection and characterization of citrus tristeza virus strains in Field 12B, with emphasis
on severe strains.
A. Dodds, D. Matthews
UCR Plant Pathology
Characterization of basic morphological and fruit quality factors for the entire NCGRCD collection.
R.R. Krueger
USDA-ARS-NCGRCD, Riverside CA
Characterization of trifoliate accessions for basic morphological characteristics and seasonal
growth characteristics.
R.R. Krueger
Screening sour orange hybrids and newer accessions for CTV tolerance and other characteristics.
R.R. Krueger
Screening rootstocks for micronutrient and salt uptake.
R.R. Krueger
Pathogen screening of CVC accessions.
R.R. Krueger
Development of efficient genetic transformation procedures for one or several commercially
important citrus cultivars in California.
A. Dandekar, D. Burger
UCD Pomology
Development of new rootstock cultivars for the desert citrus growing areas that are suitable
for lemons.
G. Wright;
K. Bowman
Univ. of Arizona, Tucson AZ;
USDA-ARS-USHRL, FL
Development of hybrid mandarin cultivars for the desert with excellent fruit quality, yield, size,
and consumer acceptance.
G. Wright
Univ. of Arizona, Tucson AZ
Revision of the taxonomy of the subfamily Aurantioideae of the Rutaceae based upon
analysis of the chloroplast and nuclear genomes.
C. Morton
Auburn Univ., Auburn AL
Genetic improvement of lemon cultivars for fresh and processed use.
B. Nielsen, B. Castle
Univ. of Florida, Lake Alfred FL
Evaluation of unique lime oils for commercial utilization.
M. Morris
A.M. Todd Company, Jefferson OR
Project initiated to increase the diversity of germplasm used in breeding Citrus scions.
J. Chaparro
USDA-ARS-USHRL, FL
Development of new rootstock cultivars.
K. Bowman
USDA-ARS-USHRL, FL
Studies on Citrus genetics
K. Bowman
USDA-ARS-USHRL, FL
32
Table 4.
Continued.
Project description
Investigator
Institution/Department
Creation of transgenic citrus trees that have fruits free from limonoid bitterness and
increased concentrations of limonoid glucosides that have pharmacological activity.
S. Hasegawa
G. Manners
USDA-ARS,
Western Regional Research Center,
Albany CA
Isolation and characterization of new limonoids from the Rutaceae plant family.
S. Hasegawa
G. Manners
USDA-ARS,
Albany CA
Evaluation of Citrus and its closely related genera using limonoids as chemotaxonomic markers.
S. Hasegawa
G. Manners
USDA-ARS,
Albany CA
Evaluation and isolation of natural products from citrus seeds which inhibit Aspergillus
growth and aflatoxin production.
G. Takeoka
USDA-ARS
Albany CA
Anticarcinogenic activity of citrus limonoids.
S. Hasegawa
G. Manners
USDA-ARS
Albany CA
Evaluation of the cyropreservation of seeds of Citrus and Citrus relatives.
C. Walters
USDA-ARS,
National Seed Storage Laboratory,
Fort Collins CO
Evaluation of the cyropreservation of vegetative materials of Poncirus trifoliata.
L. Towill
USDA-ARS
National Seed Storage Laboratory,
Fort Collins CO
document), photographs of common citrus varieties, and
a list of the CVC accessions (Appendix, this document).
and citrus relatives. Increasing demand for oral presentations and fruit displays, especially labor-intensive displays such as the Riverside Orange Blossom Festival
have necessitated hiring students as well as assembling a
group of volunteers from the Riverside County UC Cooperative Extension Master Gardeners program to help
conduct large fruit displays. Volunteers provided over
100 person-hours collecting and washing fruit in addition to hours spent setting up and taking down tents and
tables, cleaning the booth, and providing questions and
answers to the general public.
The staff of the CVC also receives numerous
phone calls, letters, and email messages from local and
international growers, nurserymen, industry representatives, state officials, and the general public requesting
access to its database on characteristics, genetic identity,
and history of specific cultivars and strains of citrus and
citrus relatives. The staff also provides fruits, and other
materials to UC faculty, specialists, and advisors as a
source of demonstration materials for their activities. In
March of 2000, the staff of the CVC provided support
for a two-day Citrus Celebration, which culminated in a
reception and dinner which honored 23 UCR researchers and two programs, the CCPP and the CVC, for their
commitment to furthering science and the advancement
of California’s Citrus Industry.
A website (http://cnas.ucr.edu/~citrus/index.
htm) has been established through the auspices of the
UCR CNAS and consists of multiple pages of basic information about the CVC including, history, goals, research projects utilizing the collection (Table 4, this
Recommendation 12. The CVC website is a potentially
valuable distribution point for CVC collection characterization and evaluation data. It may need relocation from its current status on the UCR College of Natural and Agricultural
Sciences server. The website should include contact information for the staff.
Personnel
The current curator of the CVC and the three CEBs is
employed as a Senior Museum Scientist (67% time) in
the Dept. of Botany and Plant Sciences. This position is
currently held by T.L. Kahn.
The other members of the CVC staff are a Staff
Research Associate (100% time) and work-study students who are employed 5 to 10 hours a week during the
school year and full time during the summer. The numbers of students employed varies from year to year. The
Staff Research Associate position (held by O. Bier) has
been supported on a yearly basis since 1992 by grants
from the CRB. Grants were to M.L. Roose from 1992 to
1995, since then, grants have been to T.L. Kahn and
M.L. Roose. The on-going objective of these grants is to
evaluate trueness-to-type and commercial potential of
citrus varieties distributed by the CCPP, therefore, the
SRA position only supports the CVC to the extent the
duties of evaluation coincide with CVC objectives. The
major evaluation emphasis of the CRB-supported work is
on fruit quality traits of varieties in the major production
33
regions of the state. The short-term nature of work-study
employment (and subsequent high turnover) and the
indirect service of the SRA position are not optimal arrangements for technical support for the CVC.
Financial resources
Office space, laboratory, greenhouse space, screenhouse,
administrative support, and a budget of $3,000 per year
for operating expenses for the CVC are provided by the
Dept. of Botany and Plant Sciences, UC Riverside. Miscellaneous administrative expenses such as phone calls,
photocopying, and FAX charges are paid by the CVC by
recharge. Vehicles needed for travel to and from the lab,
CVC, greenhouses, and CEBs are rented by the CVC
from the Dept. of Botany and Plant Sciences. These vehicles are expensive and only available on a first-comefirst served basis limiting planned use. The modest operating expense budget limits the quality of maintenance
and the scope of evaluation and extension activities that
can be undertaken each year.
For most of its existence, the CVC was supported
almost entirely by the host institution, the University of
California. In the past, there were small amounts of additional indirect support from research grants to E.
Nauer, D.J. Gumpf, and M.L. Roose from the CRB for
projects that utilized the CVC. Since T.L. Kahn became
curator of the CVC and the CEBs, the University of
California has provided direct support to the CVC as
salary (to T.L. Kahn, now as a 67% time Senior Museum
Scientist), as operating expenses, as office and laboratory
facilities, as administrative services, as tree maintenance
services via the UCR Agricultural Operations and the
field stations, and as funds to update and expand the
Recommendation 13. Positions and staffing levels needed
are a full-time curator, full-time technical assistant/assistant
curator, part-time seasonal assistants, and a part-time database/website specialist.
Facilities and equipment
Computers accessible for work of the CVC are one
Pentium 100MHz computer at the curator’s desk that
must serve her other activities as well and a Pentium
133MHz computer in the laboratory space provided to
the CVC by the Dept. of Botany and Plant Sciences.
Each machine has a copy of the CVC database on it, but
each is maintained separately. Currently the CVC web
page is housed on a server belonging to the UCR CNAS
and staff of the CVC do not have direct access to it.
Recommendation 14. The CVC should have at least two
up-to-date, networked computers and at least one laser-quality printer, devoted to such activities as accessioning, data
analysis and exchange, equipment and budget monitoring,
and preparation of outreach materials.
Laboratory facilities for the CVC are provided by the
Dept. of Botany and Plant Sciences. Equipment comes
from the Dept. or was purchased by T.L. Kahn with research start-up funds. However, some CVC activities
require other arrangements for equipment. For example,
for evaluations of pollen viability (Figure 21), CVC staff
currently borrows a Zeiss epifluorescent microscope from
the Dept. of Botany and Plant Sciences that is otherwise
used for teaching courses in the department. If there
were funds, a vertical illuminator could be purchased
that would update the standard microscope in the CVC
laboratory for use in fluorescence microscopy.
The main CVC field plantings are physically located about 2 miles (and 5 minutes by vehicle) from the
offices of the curator and technical assistant and the lab
facilities used by them in the Dept. of Botany and Plant
Sciences. The secondary sites (2 acres each) at Irvine
and Thermal are 1 and 1.5 hours away, respectively. Any
tools and field equipment must be stored in the laboratory and carried to the field for each use. The laboratory
size is 288 sq. ft. and not much storage is possible.
The squashed, softened stigma, one day after
pollination, reveals germinating viable pollen grains.
Pollen tube growth can be used as a measure of pollen
viability. Abnormal growth of the pollen tube structure
would be indicative of pollen-stigma incompatibility.
The pollen tubes are stained with aniline blue that is
specific for the callose which lines the walls of pollen
tubes. They are visualized with fluorescence microscopy,
a technique for which the CVC should be equipped.
Photo credit: Tracy L. Kahn.
Figure 21.
Recommendation 15. Facilities and equipment needs include research equipment, a vehicle, and a greenhouse/
headhouse structure on or near the orchard site to facilitate
propagation of new or replacement accessions and field evaluation activities, house equipment and tools, and offer a reception point for CVC visitors and tours.
34
computer database of CVC accessions ($1,500) via a
T.L. Kahn and O. Bier to provide ideas and review of
1997–98 award from the UC Genetic Resources Conserplans developed by the Walt Disney Imagineering staff
vation Program.
produced $1,000 for CVC activities. A donation of
In addition, direct extramural support for CVC
$8,000 (1999–01) from the A.M. Todd Company was
activities has come from funds awarded to T.L. Kahn
received in support of the CVC’s research program on
from USDA ARS as a Specific Cooperative Agreement
the characterization of lime varieties. While the fund
with the NCGRCD (1997: $10,000; 1998: $4,000) to
currently has only $7,378, it could serve as seed money
assist in the conservation and evaluation activities of
for an endowment fund in support of the CVC.
CVC and from the California Citrus Nursery Advisory
Board (a one-year grant in 2000 to complete conversion
Recommendation 16. The CVC needs an annual budget
of the CVC main plantings to a low-volume irrigation
for operating expenses and outreach that reflects the full costs
system and to provide remedial fruit removal and prunof these activities including maintenance on facilities and
ing and development of a brochure in preparation for an
equipment and depreciation on equipment (Table 5).
endowment fund-raising campaign). The absence of
other direct extramural support is primarily a reflection
Recommendation 17. The CVC needs funding for firstof the fact that there are not funding sources whose mistime and one-time expenses to bring its physical facilities to a
sion entails support of genetic resources acquisition and
level adequate to meet its needs as a California repository of
maintenance directly on a time scale that facilitates
citrus genetic resources (Table 5).
long-term conservation.
Other extramural funds indiTable 5. Costs of personnel, equipment, and facility requirements for
rectly support activities of the CVC.
the CVC.
The CRB awards that support the
Initial and replacement
SRA position for evaluation of acCategory
cost (dollars)
Annual cost (dollars)
cessions were described above. For
Personnel
the 1998–99 season ($12,010) and
Curator (1.0 FTE)
65,000a,b
1999–00 season ($16,841), T.L.
Kahn and M.L. Arpaia received
Technical Assistant (1.0 FTE)
40,000a,b
CRB funding for a related project
Database/website specialist (0.5 FTE)
21,000a,c
that provides a sensory evaluation of
Temporary assistance
10,000a,d
a selection of new varieties (see
Supplies
Table 4). The CVC serves as one
Nursery and lab supplies
5,000
source of fruit for these taste panels.
Acquisition, research, & evaluation
25,000e
The CVC is also the site of research
conducted by T.L. Kahn to evaluate
Equipment
factors controlling seedlessness in
Vehicle: minivan
20,000
new Clementine mandarin selecVertical illuminator and filter sets (Zeiss)
5,000
tions (see Table 4). This project
Computers (2)
5,000
which is funded by the California
Printer
600
Citrus Nursery Advisory Board
Electric
cart
5,000
(1998–99: $3,365, 1999–00: $4,125,
Services received
2000–01: $4,215) provides funding
for work-study students who are
Annual tree maintenancef
24,000
members of the CVC staff. Another
Annual tree pruning
2,000
cooperative CRB-funded mandarin
Annual fruit reduction
7,000
variety trial, being conducted by T.L.
Annual vehicle maintenance
2,000
Kahn and P. Mauk to provide the
Facility
industry with information on tree
Greenhouse (36’x60')/headhouse (20’x36')
200,000
growth, fruit quality characteristics,
Utilities for field facilities
2,000
and timing of legal maturity for selected mandarin varieties in the
Subtotal
235,600
203,000
California desert, also indirectly supContingency fund reserve
ports the CVC.
12% of annual budget
24,360
Finally, a UC Riverside FounTotal
235,600
227,360
dation account for the CVC was esa
d
includes benefits;
Work-study and summer students;
tablished in the 1980s and has reb
estimate, actual amount will depend on job title; eReserved for supplies, travel, and staffing
ceived donations in support of the
c
f
based on Computer Resource Specialist II title,
Performed currently by UCR Agricultural
CVC. For example, participation by
entry level;
Operations, does not include pruning.
35
Recommendation 18. Funding to enhance and sustain the
CVC’s role in conservation and utilization of citrus genetic
resources for California properly involves the US Government, the State of California, the University of California,
and the citrus industry.
pus, at the Research and Extension Centers (South
Coast and Lindcove), and at the Coachella Valley
Agricultural Research Station. For the UCR campus,
grant requests for land, labor, and facilities, and
progress reports must be submitted annually. For the
Research and Extension Centers, research project
proposals must be submitted for each collection at
three-year intervals and project review reports must
be submitted annually.
Recommendation 19. An endowment fund should be established with interest earned being dedicated to meet annual
operations costs of the CVC. The fund should be organized
under the auspices of the UC Riverside campus with contributions from the diverse enterprises comprising the California
citrus industry and individual donors. A committee composed
of representatives of USDA NPGS, UC, CDFA, and CRB
and individuals having strong interest in the preservation of
citrus varieties and diversity should be convened to develop
this fund.
✦ Providing the general direction and guidance for the
physical maintenance of CVC trees and accessions
maintained in portions of two greenhouses on the
UCR campus.
✦ Providing the curation, accessioning, and guidance
for the physical maintenance of the CEBs.
✦ Facilitating research projects which utilize accessions
from the CVC.
Administration
✦ Conducting research directly.
The CVC is administered by a curator employed by the
Department of Botany and Plant Sciences in the UC
Riverside College of Natural and Agricultural Sciences.
The curator has direct responsibility for the CVC collections. Close collaboration with the curators of the CCPP
and the NCGRCD provides mutual guidance for genetic
resource management issues, however, a more formal
advisory arrangement would benefit the curator.
The curator’s responsibilities include:
✦ Coordinating and, in most cases, conducting outreach
activities related to the collection and citrus genetic
diversity in general. The time required from the curator necessitated by this task has significantly increased in recent years.
Recommendation 20. The relationship of the management
of the CEBs to management of the CVC should be formalized and the extent of the effort required by the CVC curator
to manage the CEBs needs to be defined to ensure that these
activities do not come at the expense of CVC activities.
✦ Organizing, applying for, and reporting on the project
support that allows for the physical maintenance of
trees in the CVC and CEB acreage on the UCR cam-
36
➐
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40
41
42
APPENDIX
HOLDINGS OF THE UNIVERSITY OF CALIFORNIA, RIVERSIDE
CITRUS VARIETY COLLECTION (CVC)
5. Tangor
6. Tangelo
7. Calamondin and hybrid
8. Rangpur type
9. Navel orange
10. Valencia orange
11. Blood orange
12. Other sweet orange and hybrid
13. Sour orange and hybrid
14. Pummelo (shaddock)
15. Pummelo hybrid
16. Grapefruit
17. Grapefruit hybrid
18. Miscellaneous Citrus species
19. Citrus subgenus Papeda and hybrid
20. Kumquat and hybrid
21. Trifoliate
22. Trifoliate hybrid
23. Miscellaneous species, not genus Citrus
THE TABLE ON THE FOLLOWING PAGES lists the 865 accessions currently maintained in the CVC. The accessions are identified in the CVC by a unique Citrus Research Center (CRC) number. In addition to an Accession name or description field, the table also provides a
Variety Introduction (VI) number given to accessions
cleaned by the Citrus Clonal Protection Program
(CCPP) and a Plant Introduction (PI) number assigned
to accessions listed in the US Dept. of Agriculture’s Genetic Resource Information Network (USDA GRIN)
database. The Source field provides information on the
source, intermediary, and geographic origin when
known. The Date field identifies the year in which the
accession was acquired by the CVC.
The accessions are grouped by the major citrus
type to which they are assigned and ordered by CRC
number within these groups. The groups are presented in
the following order:
1. Citron and hybrid
2. Lemon, lemon-type
3. Lime, lime-type
4. Mandarin
43
44
Appendix. Holdings of the University of California, Riverside Citrus Variety Collection
Category
CRC
numbera Accession name or descriptionb
Other identifiers
VI
PI
numberc numberd Sourcee
Datef
1. Citron and hybrid
0138-A
0138-B
0294
0648
0661
1795
2456
2847
3055
3174
3190
3241
3487
3518
3519
3520
3521
3522
3523
3526
3527
3529
3530
3531
3532
3533
3534
3535
3536
3546
3654
3655
3723
3755
3768
3798
3819
3878
3891
Indian citron (ops)
Indian citron (ops)
Ponderosa “lemon” (probable Citron ´ lemon hybrid)
Orange-citron-hybrid
Indian sour citron (ops) (Zamburi)
Corsican citron
Citron or citron hybrid (came in as Djerok which is Dutch word for “citrus”
Yemen citron
Bengal citron (ops) (citron hybrid?)
Unnamed citron
Dabbe (ops)
Citrus megaloxycarpa (ops) (Bor-tenga) (hybrid)
Kulu “lemon” (ops)
Citron of Commerce (ops)
Citron of Commerce (ops)
Corsican citron (ops)
Corsican citron (ops)
Diamante citron (ops)
Diamante citron (ops)
Etrog citron (ops)
Hiawassie citron (ops)
Indian citron (ops)
Italian citron (ops)
Mexican citron (ops)
Papuan citron (ops)
Philippine citron (ops)
Sicily citron (ops)
Spadifora citron (ops) (Citrus medica var. Spadifora)
Yemen citron (ops)
South Coast Field Station citron
Dulcia citron (ops)
Odorata citron (ops) (Tihi-Tihi)
Badhri “lemon” (ops)
Limau Mata Susu (ops)
Fingered citron (Buddha’s Hand citron)
Citrus medica var. Yunnanensis
Citron type
Arizona 861 S-1 citron seedling (Etrog type)
Ethrog citron
409
369
357
426
539413
539414
539491
539238
31981
539415
539416
105957
539417
230626
539418
539446
539207
539419
539420
539421
539422
539423
539424
539425
539426
539427
539428
539429
539430
539431
539432
539433
539434
539435
539436
539437
539438
539439
539445
600630
539440
600651
508265
India
India
Fawcett’s #127, Florida collection
Mr. Flippen, between Fullerton and Placentia CA
USDA, Chico Garden
W.T. Swingle, USDA
From CPB
Bureau of Plant Introduction
Ed Pollock, NSW, Australia
H. Chapot, Rabat, Morocco
Fruit Research Station, Burnihat Assam, India
A.G. Norman, Botanical Garden, Ann Arbor MI
John Carpenter, USDCS, Indio CA
SCFS 25-3-17
L.C. Knorr, US-AID, Punjab Agr. Univ., Ludhiana, India
Richard A. Hamilton, University of Hawaii
Budwood import from Hawaii, via CCPP
Prof. Tsuin Shen, Peking Agric. Univ., Peking, China
1912
1912
1914
1915
1915
1924
1930
1954
1955
1959
1957
1963
1966
1966
1966
1966
1966
1966
1966
1966
1966
1966
1966
1966
1966
1966
1966
1966
1966
1968
1968
1969
1971
1975
1980
Selected seedling of Ariz. 861 citron
Israel, via Glenn Dale & CCPP
1983
539292
600625
539268
539313
539281
539325
539211
539257
539193
539204
539287
539258
539315
539316
539288
539289
539290
103496
539444
539317
539179
133875
133731
539318
539319
539293
Grove in Glendora CA
Fawcett’s #175. Seed rec’d from A. Melson, Florida
J.W. Mills, Pomona CA
J.W. Mills, Pomona CA buds from tree 1195
Chase lemon grove, Corona CA
Riverside Station grounds (see notes below)
A.C. Turner, Salisbury, Rhodesia
Philippine Islands (via CPB)
CPB
CPB
South Africa?
Home garden, D.W. Field, Burbank CA
Detweiler grove, Alta Loma CA
M.H. Brayard, Marrakech, Morocco
Rabat, Morocco
Simla Hills, India (via CPB & Florida)
India (via PI, USDA)
Beverly Hills CA
Cascade Ranch 8-16-1
UCLA
Fd 21, R-47, CRC, Riverside
Lasscock’s Nursery, South Australia
2nd budded generation from sdlg of o.l. Rubidoux No. RT 765
Sloop, Oceanside
Mr. Kipp, Upland CA
2. Lemon, lemon type
0280
0390
0400
0565
0569
0599
0710
1222
2317
2322
2323
2325
2367
2429
2477
2489
2544
2557
2695
2703
2881
2899
3001
3005
3007
3009
Villafranca lemon
Villafranca lemon
Florida rough lemon (ops)
Genoa lemon (Eureka type)
Millsweet lemon
Eureka variegated lemon
Chinese lemon
Mazoe lemon (ops)
Limon Real
India- lemon
India lemon
South African rough lemon
Variegated Pink Fleshed Eureka lemon
Amber lemon (Eureka type)
Khobs-el-arsa
Rhobs-el-arsa (ops)
Indian rough lemon (ops)
Gomiri rough lemon (ops)
Faris sweet lemon
Cascade Eureka lemon
Bergamot
Italian pink fleshed lemon
Seedless Lisbon
Frost nucellar Eureka lemon
Allen Variegated Eureka (Sloop)
Messina lemon
76
486
77
420
492
21
45
1914
1914
1914
1914
1914
1914
1909
1919
1930
1930
1930
1931
1932
1933
1935
1932
1933
1938
1939
1951
1953
1953
Category
CRC
Other identifiers
VI
PI
Datef
2. Lemon, lemon type (cont.)
3010
3013
3043
3045
3050
3060
3063
3093
3154
3155
3159
3162
3173
3176
3185
3193
3194
3199
3200
3261
3265
3300
3385
3386
3387
3388
3389
3390
3392
3396
3491
3492
3496
3498
3499
3500
3501
3504
3505
3506
3590
3591
3593
3737
3748
3834
3835
3836
3837
3838
3839
3840
3841
3879
3885
3892
3893
3894
3924
3925
3970
3989
3996
4005
4014
Kaweah #1 Lisbon lemon (1-1-1)
Lupe Lisbon lemon (ops).
Corona (Foothill) old budline Eureka lemon
Kulu lemon seedling (Gombru)
Volckamer lemon (ops)
Citrus jambhiri (ops)
Jullundri Khatti (ops)
Sweet lemon (ops)
Citrus species (ops) (Lemon- Morocco)
Citrus species (ops) (lemon type)
Lunario lemon (ops)
Iran lemon
Citrus assamensis (lemon ´ citron?)
Frost nucellar Lisbon lemon
Stow red rough lemon
Paak ling mung lemon (ops)
Kusner lemon
Soh long lemon (ops)
Limoui sangui (ops)
Soh synteng lemon (ops)
Bitrouni lemon (ops)
Wild lemon (ops)
Florida rough lemon “A” (ops)
Estes rough lemon (ops) (Florida ro. lem.“B”)
Arancino (Coccuzzaro) lemon (ops)
Femminello Ovale lemon (ops)
Femminello Sfusato lemon (ops) (elongate)
Lo Porto lemon (ops)
Monachello lemon (ops)
Milam lemon (ops) (Clone X- rough lemon type)
Primofiore lemon (ops)
Iraq lemon (ops) (Sweet)
Allen-Newman #4 op Eureka seedling
Cascade op Eureka seedling #1
Blanchard op Eureka seedling
Femminello (ops) (Lisbon type)
Limoneira Olivelands 8-A Lisbon (ops)
Dr. Strong Lisbon (ops) #28
Prior Lisbon (ops) #1
Bergamotto (ops) #18 (Lisbon type)
Berna lemon (ops)
Corpaci lemon (ops)
Interdonato lemon (ops)
Improved Meyer lemon
Citrus species (ops), lemon type
Limoneira rough lemon (ops)
Galligan Lisbon lemon (ops)
Foothill Lisbon (ops)
Cook Eureka (ops)
Ross Eureka (ops)
Monroe Lisbon (ops)
Rosenberger Lisbon, old budline
Nicaraguan lemon
Schaub rough lemon
Local variety of lemon from Iran
Mesero lemon
Ricote lemon
Santa Teresa #1 lemon
Peretta
Lumia
Limonero Fino
Limonette de Marrakech (Marrakech Limonette)
Vangasay rough lemon
“Local” lemon from Cyprus (Lapithiotiki lemon)
Taylor Eureka lemon
347
407
280
346
68
345
319
194
232
228
108
113
372
406
423
444
445
480
573
493
512A
528
539326
539327
539320
539294
539335
539259
539260
539278
230834
230832
218009
539295
235991
539328
539261
93379
119828
254729
539214
254730
539297
241118
539262
539263
539298
539299
539300
539301
539302
539264
539303
539314
539304
539321
539322
539329
539305
539306
539330
539180
539307
539308
230373
539447
539208
539265
539331
539332
539323
539324
539333
539334
539209
539266
431462
209862
209863
227692
539210
539310
539311
539280
539267
539312
600661
46
Kaweah Lemon Co., Lemon Cove CA
Claremont CA
Foothill Ranch, Corona CA. R-25, T-1, Hill St.
J.F.L. Childs, USDA Station, Orlando FL
Acireale, Sicily
Dept. of Agric., Lyallpur, Punjab, India
Dept. of Agric., Lyallpur, Punjab, India
H.S. Gentry, Shiroz, Iran
Vientiane (Laos) Indo China through Rabat, Morocco
Vientiane (Laos) Indo China through Rabat, Morocco
Frank Russo, Acireale, Sicily Italy
Joe Furr, USDCS, Indio CA
Mr. Mawsing Rharasti, Shilbong, Assam
Seedling clone from Rubidoux Tract old-line Lisbon
Stow Ranch, Goleta, CA
Seeds from fruit grown at plant introd. GH, Riverside
UCLA Variety block, originally from Russia
Fruit Exp. Sta., Shillong, India
Govt. Fruit Exp. Sta., Shillong, India
Drs. Grassl & Warner, Kusawun, near Wewak, N. Guinea
Harry Ford, Cit. Exp. Station, Lake Alfred FL
Harry Ford, Cit. Exp. Station, Lake Alfred FL
Acireale, Sicily, Italy (via L.J. Klotz, CRC)
Acireale, Sicily, Italy (via L.J. Klotz, UCR)
Acireale, Sicily, Italy (via L.J. Klotz, CRC)
Harry Ford, Lake Alfred FL
Joe Furr, USDCS, Indio CA B1-5-1-3
Bagdad, Iraq, via Beltsville as cuttings.
Domingo Hardison, La Campana Ranch, Fillmore CA
Domingo Hardison, Olivelands 4-B, R-7, T-28, Limoneira R.
Domigno Hardison, La Campana Ranch Fillmore CA
Joe Furr, USDCS, Indio CA B1-5, R-1, T-7
Joe Furr, USDCS, Indio CA 5-1-11
CCPP VI 319 stock plant at Rubidoux screenhouse.
Lindcove Field Station
Santa Barbara C.V.O. via CCPP
Willits & Newcomb, Thermal, via CCPP
Willits & Newcomb, Thermal, via CCPP
Hardison Ranch, Santa Paula, via CCPP
Limoneira Olivelands, via CCPP
Utt Development Co., Oxnard CA, via CCPP
Import by W. Reuther, probably from Nicaragua
“Mother” tree, J. Carpenter, USDCS, Indio CA
Iran, via Glenn Dale & CCPP
Spain, via Glenn Dale & CCPP
Sicily, via Glenn Dale & CCPP
Glenn Dale Quarantine Facility, import from Italy
Glenn Dale Quarantine Facility import from Italy
Spain?
Morocco
Florida - Budwood Registration Program- Winter Haven
N. Vakis, Ministry of Agric., Cyprus
Australia
1953
1953
1954
1954
1955
1954
1954
1955
1956
1956
1956
1957
1956
1917
1959
1958
1960
1959
1959
1959
1959
1957
1963
1961
1962
1962
1962
1962
1962
1959
1965
1963
1966
1966
1966
1966
1966
1966
1966
1966
1965
1968
1965
1971
1971
1962
1963
1963
1960
1960
1978
1976
1983
1979
1955
1955
1959
1984
1984
1987
1987
1988
1989
1989
Category
CRC
Other identifiers
VI
PI
Datef
3. Lime, lime type
0363
0391
0449
0450
0919
0921
1482
1684
1710
1813
2188
2315
2449
2450
2458
2459
2484
2683
2709
2883
3051
3069
3070
3072
3172
3603
3604
3762
3772
3776
3822
3997
Sweet lime
Tahiti lime
Ponds seedless lime
Wilder seedless lime
Citrus limettoides (sweet lime)
Citrus limettoides- Risso (sweet lime)
Palestine sweet lime (Indian sweet lime)
Weirick sweet-red lime
Mexican lime (West Indian, Key)
West Indian lime (Mexican, Key)
Key lime (ops) (Stow #7) (West Indian, Mexican)
Page lime (Tahiti type)
Everglade lime (West Indian type)
India lime
Perrine lemon (lemonime)
Lemonime
Sniff sweet red lime
Thornless Mexican lime
Otaheite red acidless lime (Citrus tahitensis)
Egyptian lime (ops)
Mitha-Tulia
Warren limequat
India lime sport
Addanimma (ops)
Tavares limequat
Eustis limequat (ops)
Lakeland limequat (ops)
Abhayapuri lime
Bearss lime
Bakrai (acidless lime)
Mexican lime type
Rangpur lime ´ Troyer citrange [814-12-47-X-E]
81
419
175
358
483
539285
539273
539274
539275
539286
37772
539283
539284
539151
539152
539153
539271
539154
539155
539205
539206
539282
539156
539343
185427
539277
539802
539213
539212
539804
539806
539807
539157
539272
539279
600629
539267
Fawcett’s #15 sel.-F.S. Earle, Herradura, Cuba
Hart’s grove, San Dimas CA
Webber’s #17, from garden of Mr. Damon, Moanalua Gardens, Honolulu
Webber’s #18, from Garrett Wilder, Honolulu
Fortunato da Silva’s grove, Cabulla, Bahia (thru USDA)
from USDA
W.T. Swingle, USDA
Mrs. W.C. Weirick, Box 254, Lincoln CA (Placer County)
Mel Anderson, Fruit Growers Supply Co.
Tree on ranch S.W. of Indio CA
Harvey grove, West Palm Beach FL
Residence of Mrs. A.D. Page of Fallbrook CA
From CPB
From CPB
From CPB
From CPB
Sniff Date Gardens, Indio CA
Marcy Ranch, Tustin CA
Y.Carmon, Tel Aviv, Israel
Dept. of Agric., Lyallpur, India
Mavro Warren Ranch, Foothill Rd., Ventura CA
Sport lime from India lime, Fld. 18A R-33 T-2, CRC
Ed Pollock, Parkes, N.S.W., Australia
Lyndon Maxwell, Sunnymead CA
Richard A. Hamilton, Univ. of Hawaii
Willits & Newcomb, Thermal, via STG and CCPP
Kaserun, Iran
Tree in UCR Field 21D
Florida - Budwood Registration Program, Winter Haven
1914
1914
1914
1914
1916?
1916?
1924
1927
1927
1928
1928
1932
1931
1930
1931
1931
1933
1937
1937?
1949
1943?
1956
1957
1956
1957
1968
1968
1971
1977
1975
1988
4. Mandarin
0279
0300
0303
0602
0696
1851
2331
2376
2448
2485
2590
2692
2710
2893
3019
3020
3021
3022
3026
3085
3143
3144
3147
3150
3177
3178
3226
3228
3239
3260
3280
3292
3297
Clementine (Algerian) mandarin
Parson’s special mandarin
King mandarin (tangor?)
Dancy mandarin (Weshart nucellar)
Kinokuni mandarin (ops) (Citrus kinokuni)
Kawano Wase Satsuma mandarin
Unnamed mandarin
Tien Chieh mandarin
Citrus depressa (C. pectinifera) (Shekwasha)
Citrus amblycarpa seedling (Nasnaran)
Tien Chieh mandarin seedling
Tim Kat mandarin (Timkat, Citrus oleocarpa?)
Citrus depressa (C. pectinifera) (Shekwasha)
Laranja Cravo (Tangerine Cravo, Cravo)
Kara mandarin
Wilking mandarin
Kinnow mandarin
Frua mandarin
Dancy mandarin (Frost nucellar)
Szinkom mandarin (ops)
Citrus sunki mandarin (ops)
Citrus keraji (ops)
Citrus leiocarpa (ops) (Koji)
Citrus tachibana (ops)
Honey mandarin
Satsuma, Frost nucellar #1 (Owari)
Scarlet Emperor mandarin (ops) Pankan
Citrus nippokoreana (ops) (Korai Tachibana)
Citrus reticulata (ops)
Soh niamtra mandarin (ops)
Citrus succosa (ops) (Jimikan)
Citrus erythrosa (ops) (Kobeni-mikan)
Citrus tardiva (ops) (Giri-mikan)
9
154
2
66
1
32
133
33
539183
539497
539456
13005
539270
539688
539493
539494
109754
93602
539495
14007-A
539189
539496
539498
539499
539500
539501
539683
539502
539678
539269
539276
539679
539503
539689
539454
254732
254779
539675
539190
539684
47
Chico Gardens, Chico CA
P.J. Wester, Lamao, Bataan, Philippine Islands
French Gilman, Banning, CA
PR China (via CPB)
From CPB
From CPB
From Beltsville MD
USDA, Washington DC
USDA, Torrey Pines CA
Plant Introduction growing in Fld. 12 nursery
Hybrid produced at CRC
Nucellar produced at CRC
Bureau of Plant Industry, Manila, Philippines
Hiroshi Yoshimura, Univ. of Osaka, Japan
Ted Frolich, UCLA
H.B. Frost hybrid of King ´ Willowleaf
H.B. Frost seedling from Rubidoux Tract old-line Satsuma
Ted Frolich, UCLA
Y. Tanaka, Shizuka Pref., Japan
Ted Frolich, UCLA
Ted Frolich, UCLA, originally from Japan as seed.
Ted Frolich, UCLA, originally from Japan
1914
1914
1914
1914
1915
1928
1930
1930
1930
1932?
1935
1938?
1937?
1954
1956
1956
1956
1958
1915
1916
1960
1957
1959
1959
1960
1960
1960
Category
CRC
Other identifiers
VI
PI
Datef
4. Mandarin (cont.)
3329
3346
3363
3367
3405
3466
3558
3559
3560
3564
3568
3569
3576
3577
3613
3615
3616
3649
3659
3727
3731
3738
3752
3773
3794
3809
3812
3813
3816
3817
3820
3843
3844
3845
3846
3847
3848
3849
3850
3851
3852
3853
3880
3887
3895
3897
3906
3910
3913
3953
3956
3958
3960
3965
3972
3973
3974
3975
3986
3987
3988
3990
3991
3992
3999
4003
Richard’s Special mandarin (ops) (Ponkan)
Kunembo mandarin (ops)
Beledy mandarin (ops)
Mandarine sanguine seedling
Mandarinette, (ops)
Citrus yatsushiro (ops)
Fremont mandarin
Fairchild mandarin
Fortune mandarin
Citrus lycopersicaeformis (ops) (Monkey orange)
Pixie mandarin
Encore mandarin
Canton mandarin
Changsha mandarin (ops)
Empress mandarin (ops)
Nova mandarin (ops)
Page mandarin
Bower mandarin hybrid seedling
Batangas mandarin (ops)
Nagpur “orange” (Ponkan)
Clementine ´ Silverhill Satsuma
Necked “orange”, seedling #1 (Som-Chuk)
Som Keowan (ops)
Clementine Monreal mandarin
Dobashi Beni Satsuma mandarin
Sunburst mandarin
Kinkoji Unshiu
Kobayashi Mikan
Okitsu-wase Satsuma mandarin
Willowleaf mandarin nucellar
Cleopatra mandarin (ops)
King tangor (mandarin) (ops)
Murcott mandarin (ops)
Hill mandarin (ops)
Nepolitana Satsuma mandarin
Ponkan mandarin (ops) (Swatow)
Robinson mandarin (Clementine x Orlando)
Lee mandarin (Clementine ´ Orlando)
Som Kaeo II (Crystal mandarin)
Som Saa mandarin
Citrus yatsushiro
Citrus kinokuni - ‘Mukakukishu’ (Kinokuni mandarin)
“Yellow Rind” mandarin
Huang Yen Man Chieh mandarin
Seedless Kishu
Daisy mandarin (Fortune ´ Fremont)
Gold nugget mandarin (6D-32-1, Pixie-like)
W. Murcott (Afourer) mandarin
Novelty ´ Ellendale mandarin
Koster mandarin (Ellendale?, Ellendale Beauty?) (tangor?)
Ellendale mandarin (tangor?)
NISSV E (mandarin hybrid)
(Temple ´ Dancy) ´ Encore— JWC Priority #1
Citrus erythrosa (Kobeni-mikan)
Clementine Caffin mandarin
Clementine Sidi Aissa
Fallglo mandarin (USDA 88-1)
Lee ´ Nova (USDA 88-2)
Robinson ´ Lee (USDA 88-3)
Clementina Fina (Sodea)
Sun Chu Sha mandarin
247
246
248
10
156
282
58
281
360
366
377
392
393
389
118
329
235
147
365
311
200, 416
198
395
402
433
382
422
462
523
499
464
482
485
490
506
509
491
508
484
501
488
498
497
539504
539455
120523
105006
263547
539712
539507
539508
539509
539347
539510
539511
133733
539512
539513
539514
539710
539515
539516
49851
539517
539518
539519
247751
358061
539520
433931
433932
433260
433261
436688
539188
539492
539457
539521
539522
539690
539523
539524
539525
539526
539527
433272
433259
539528
539529
539530
539531
539532
539533
539534
539535
539536
539216
539537
539538
539539
539540
539191
539184
539185
539541
539542
539543
539186
539544
48
Ted Frolich, UCLA
Variety Coll., USDA Station, Orlovista, Florida
Ted Frolich, UCLA Var. Coll. R-5, T-2
Okitsu, Shizuoka Pref., Japan (via W.P. Bitters, CRC)
D. Singh, Indian Agr. Research Inst. New Delhi, India
CRC 12D-2-7, new cultivar dev. At CRC
Hybrid of King ´ Willowleaf produced at CRC, Riverside
Ted Frolich, UCLA Var. Block R-6, T-16.
John Cree, Jr., Texas AES #19, Crystal City TX
South Africa, Dept. of Agric., Nelspruit
Seedling from CRC 2333, 8A-26-29
Nagpur, Central Provinces, India (via Glenn Dale & CCPP)
USDCS, Indio CA
Thailand – Imported as seed by W. Reuther, CRC
Dept. of Agric., Bangkok, Thailand
Import from Sicily, via Glenn Dale and CCPP
Budwood import from Japan, via Glenn Dale, Thrmo, CCPP
Florida, via CCPP
PR China, via Glenn Dale
Japan, via Glenn Dale & CCPP
Nucellar seedling budline produced at CRC
Seedling derived from CRC 1461
Seedling produced by Plant Breeding at CRC
USDCS Indio CA – via CCPP
Seed import, probably from India
Seed import from Colombia, South America, via W. Reuther
Seedling from Ponkan, CRC 2593
Florida
Florida
Thailand, via W. Reuther, CRC
Thailand, via W. Reuther, CRC
PR China, via R. Scora, CRC
Seedling of PI 71233, an import from China
Japan via Glenn Dale (requested by W.P. Bitters)
USDCS (Fortune ´ Fremont)
CRC – Budwood supplied by J.W. Cameron
Morocco
South Africa
South Africa
Australia
South Africa
UCR breeding plot: 6D-11-14
PR China
Morocco
Morocco
Florida – A.H. Whitmore Foundation Farm, Leesburg
Florida – A.H. Whitmore Foundation Farm, Leesburg
Florida – A.H. Whitmore Foundation Farm- Leesburg
Morocco (sent by Ray Copeland)
Florida (Jack Hearn, Orlando)
1962
1960
1960
1960
1960
1963
1966
1966
1966
1962
1966
1966
1960
1963
1964
1968
1968
1968
1966
1969
1971
1971?
1970
1977
1979
1979
1979
1979
1979
1979
1980
1933
1961
1931
1961
1965
1967
1961
1962
1962
1970
1970
1979
1979
1984
1970
1983
1980
1985
1985
1985
1985
1987
1987
1987
1987
1987
1987
1987
1988
1988
1988
1987
1989
Category
CRC
Other identifiers
VI
PI
Datef
4. Mandarin (cont.)
4010
4011
4012
4019
4020
4021
4030
4031
Clementina Oroval
Clementina Fina
Clausellina
Temple ´ Minneola
Clementine ´ Pearl
Temple ´ Dancy
Kuno Wase Satsuma
Rubidoux mandarin
517A
518B
516A
545
546
547
555
572
600644
600645
600646
600655
600654
600653
600666
600664
Luis Navarro, Valencia, Spain IVIA 8-34
Thermal Plaza
Thermal Plaza
Thermal Plaza
1990
1990
1990
330
539239
539685
Received from CPB
F. Heiney, Brawley CA
1930
1935
149464
539240
539241
539178
539242
539195
539243
539244
539245
539256
539246
539247
Glenn Dale MD
CRC, Riverside
H. Yoshimura, Univ. of Osaka, Japan
H.B. Frost hybrid
Ted Frolich, UCLA
Ted Frolich, UCLA
Florida, via CCPP
Seed from CRC 2224, old budline Tankan
Japan
Japan
Japan
1945
539695
539696
539697
539698
539699
539700
600633
539701
539702
539703
539704
539705
539706
132372
149429
149430
539707
539708
539709
539711
Date Gardens, Indio CA
Gordon Wallace, Nurseryman
Sexton place, Vero Beach FL
CPB, USDA
CPB, USDA
USDA, WashingtonDC
USDA, Sacaton AZ
USDA, Torrey Pines CA
USDA, Sacaton AZ
USDA, Sacaton AZ
Collected by H.J. Webber
Jamaica
Glenn Dale MD
Glenn Dale MD
Hybrid produced at UCR
Originally from USDA, Sacaton AZ. See CRC 2610
USDCS, Indio CA, via CCPP
539349
539840
539215
539803
539350
539351
USDA, Washington DC
USDA, Sacaton AZ
W.C. Cooper, Weslaco TX
Bureau of Plant Industry, Manila, Philippines
Paul Peters, Altadena CA
Budsport from CRC 2592, 12D-24-13
1935
1936
1946
1954
1954
1968?
539338
539345
539158
539339
600626
539341
539342
600631
539336
539337
539344
Hale’s ranch, Santa Barbara CA
Webber’s #20, from Garrett Wilder, Honolulu
J. Sexton, Santa Barbara CA
From CPB
New South Wales, Australia (via CPB)
From CPB
Roy K. Bishop, Orange CA
G.J.A. Terra, Buitanzorg, Java
1912
1914
1915
1930
1930
1930
1930?
1948
1975?
1975?
1985
5. Tangor
2224 Tankan tangor (also considered a mandarin)
2598 Temple tangor (called Temple orange and
Royal mandarin in commercial trade)
2792 Altoona
3018 Dweet tangor
3096 H-56 tangor (Willowleaf mand. x Valencia or.)
3149 Citrus benikojii (ops) (tangor)
3183 Mency tangor (Mediterranean swt ´ Dancy mandarin)
3274 Citrus funadoko (ops)
3368 Ortanique tangor seedling
3810 Sue Linda Temple tangor
3875 Tankan tangor
3946 Miyauchi Iyo (Citrus iyo, Iyo, Miyauchi Iyokan)
3952 Kiyomi tangor H-12
3980 Iyo (Iyomikan tangor)
412
343
370
455
461
538
1957
1956
1915
1960
1960
1978
1958
1984
1985
1987
6. Tangelo
2011
2012
2013
2418
2543
2559
2560
2586
2603
2604
2606
2609
2746
2780
2787
2788
2849
3331
3340
3874
San Jacinto tangelo
Wekiwa tangelo
Thornton tangelo
Sampson tangelo seedling
Sexton tangelo (ops)
Yalaha tangelo
Early tangelo
Siamelo seedling
Clement tangelo
Seminole tangelo
Sunrise tangelo
Sacaton tangelo
Webber tangelo
Ugli tangelo (ops)
Williams tangelo
Sunshine tangelo
Pearl tangelo
Sacaton tangelo (ops)
Minneola tangelo seedling
Orlando tangelo nucellar
201
138
128
174
19
1930
1930
1933
1932
1934
1934
1937
1936
1936
1936
1936
1937
1942
1945
1945
1960
1961
1958
7. Calamondin and hybrid
2592
2619
2867
3073
3087
3656
Calamondin seedling (Citrus mitis, Chi Chieh)
Citraldin (trifoliate ´ Calamondin)
Calashu (ops)
Philippine Calamandarin (ops)
Variegated calamondin
Calamondin sport
408
475
8. Rangpur type
0131
0452
0712
2318
2319
2424
2451
2875
3919
3920
3932
Santa Barbara Rangpur lime
Kusaie lime
Santa Barbara red lime
Philippine red lime (Rangpur type)
Australian red lime (Rangpur type)
Borneo Rangpur lime
Bishop red lime (Rangpur type)
Japansche citroen (ops). (Rangpur lime type)
Citrus limonia
Citrus limonia
Citrus limonia V. hangleson
49
Import, probably from Turkey
PR China
Category
CRC
Other identifiers
VI
PI
Datef
9. Navel orange
0065
0287
0574
0588
0609
0956
0969
0983
1203
1241-A
1241-B
1379
1381
2008
2853
3014
3017
3033
3135
3181
3305
3306
3307
3315
3320
3328
3354
3406
3645
3732
3791
3792
3803
3808
3903
3964
3971
3994
4013
4015
4022
4023
4024
4037
4038
4039
4040
4041
Seedy navel orange (ops)
Navelencia orange
Smith’s early navel orange
Golden Buckeye navel orange
McFadden ribbed navel
Washington navel seedling (seedy)
Thomson navel orange
Thomson navel orange
Vari navel orange
Parent Washington navel
Parent Washington navel
Golden Nugget navel
Corrigated Thomson navel orange
Carter navel orange
Paradise navel orange
Newhall Navel
Gillette navel orange (Washington)
Frost Washington navel orange, nucellar
Fischer navel orange (aka Fisher navel)
Ruvel orange (Frost nucellar line) (Rubidoux navel)
Navel orange (ops) [44944-A]
Navel orange (ops) [44944-B]
Dream navel (ops)
Rio Grande navel (ops)
Workman navel (ops) (Summernavel)
Solid Scarlet mandarin (ops)
Dry navel orange (seedling of Navelencia)
Bey navel orange (ops)
Fischer navel (ops)
Cluster navel sport
Atwood navel, old budline
Robertson navel, old budline
Lane Late navel
Leng navel
Fukumoto navel orange
Palmer navel (nucellar)
Skaggs Bonanza navel
Cara Cara pink fleshed navel [104 (STG S-1-11)]
Palmer navel orange
Navelina navel orange
Navelate navel orange
Robertson navel
Spring navel
Autumn Gold
Barnfield
Chislett
Powell
Summer Gold
338
363
364
352
353
430
507
515
471
539584
539601
600659
539582
539583
539585
539586
539587
539558
539559
539560
539561
539562
539563
146569
539564
539565
539566
539567
539604
539568
539569
539570
539571
539572
539505
539573
262348
539574
539575
600627
539576
362329
362330
539577
539578
539579
539580
526
532
548
563
567
600662
600660
600652
600672
600673
376
15
387
381
27
106
350
437
348
Pomona Experiment Station
Rubidoux Tract variety block buds from tree 1125
Rubidoux Tract variety block- buds from tree 53
T.L. McFadden, RFD #2, Fullerton CA
USDA #2—thru A.D. Shamel, Agt., Riverside
USDA #16—thru A.D. Shamel. Agt., Riverside
George C. Roeding
Buds taken from Parent Washington navel tree (see below)
Buds taken from Parent Washington navel tree (see below)
A.D. Shamel, USDA
A.D. Shamel, USDA
Armstrong Nurseries
Plant Introduction
Newhall Ranch
Fay Gillette, Hemet
Seedling produced at CRC
Armstrong Nurseries, Ontario CA
Seedling from Rubidoux Tract tree of unknown origin
William Cooper, USDA, Weslaco FL
William Cooper, USDA, Weslaco FL
Phillip Reece, USDA, Orlando FL (2-10-7)
William Cooper, USDA, Weslaco TX (Source: TAES 9-13)
East Highlands Orange, Co. East Highlands CA
Ted Frolich, UCLA Variety Block R-8, T-2a
Variety block, Rubidoux – tree 52. See CRC #585, dead file
Seedling from CRC, 8A-26-11
CRC Field 7D, R-32, T-9
Russ Davis, Ivanhoe, via STG & CCPP
Cairns orchard via STG & CCPP
Australia, via Glenn Dale & CCPP
Australia, via Glenn Dale & CCPP
Japan via Glenn Dale (requested by W.P. Bitters
Import from South Africa
Lindcove plot – originally from Willits & Newcomb
Florida (originally came to FL from Venezuela from:
Budwood Registration Prog., Winter Haven)
South Africa
Spain
Spain
1910
1914
1914
1914
1914
1916?
1916?
1916?
1919
1918
1920
1923
1923
1930
1945
1954
1953
1958
1915
1959
1959
1960
1959
1959
1960
1960
1960
1968
1967
1978
1978
1973
1973
1983
1985
1988
1988
1985
1990
Australia via B&Z Nursery
10. Valencia orange
0272
0314
0570
1240
1518
2689
2750
2776
3025
3030
3031
3032
3339
3872
3955
3963
Valencia orange (probably)
Hart’s late Valencia orange
Hart’s Tardiff (Valencia) orange
Fuzzy Valencia orange-bud sport
Valencia coarse orange
San Marino Valencia orange
Olinda Valencia orange seedling
Seedless Valencia orange
Lue Gim Gong sweet orange (ops) (Valencia)
Cutter Valencia nucellar seedling
Frost nucellar Valencia
Campbell Valencia seedling
Werley Valencia orange o.p seedling
D. Joao (Don Juan) sweet orange (Valencia type)
Midknight Valencia
Delta Valencia (Delta Seedless)
30
240
28
301
460
474
339655
539662
539668
539652
539653
539654
539656
539657
539658
539659
539660
539661
539663
210341
539664
539665
50
J.W. Mills, Pomona CA buds from tree 1199
Laidlaw grove between Ontario & Pomona Ca
Limoneira Ranch, Santa Paula Ca
San Marino Ranch, San Marino CA
Ollie Smith Olinda, CA (Carbon Canyon)
Buds from tree east of Director’s residence
Riverside, CA
Earl Campbell, Fairhaven Street, Orange CA
J.C. Werley, Bailey Flats CA
Portugal, imported by J.W. Cameron via Glenn Dale
1914
1914
1914
1918?
1925
1938
1939
1942
1942?
1960
1963
1985
1985
Category
CRC
Other identifiers
VI
PI
Datef
10. Valencia orange (cont.)
3995 Rhode Red Valencia
4001 Variegated Valencia orange
487
539666
539667
UCR Field 5B-3-1 – sport on high southeast
1988
1989
539547
238796
218019
539548
539549
230388
229987
539620
539550
539551
539552
539553
539554
539556
539557
600656
600665
Burris grove, Riverside CA
Inst. Nacional de Investigaciones Agronomicas, Spain
Plant Introduction greenhouse, Riverside (CRC)
Field 6A, R-6, T-9, CRC
Seedling from CRC #2796, produced at CRC
USDCS, Indio CA
Seedling budline grown by W.P. Bitters at CRC
USDCS, via CCPP
1933
1957
1959
1960
1967
1968
1968
1981?
539651
539594
539597
539599
539602
539606
539615
539616
539649
539650
37793
37782
539588
539589
539590
539591
539592
539593
539595
539596
539598
539600
539603
539605
539607
105009
123983
539608
539609
539610
105008
262347
539687
539546
539611
539612
539613
539614
230379
230080
539617
539618
539619
539621
C.D. Hubbard, San Fernando CA
Fawcett’s #58, from Soar’s nursery, Miami FL
Fawcett’s #63, from Heintz, City Point FL
Col. J. de Tieve e Argollo, Agua Comprida, Bahia, Brazil – through USDA
Miguel de Teives e Argollo’s grove, Roma, Bahia, Brazil – through USDA
E.R. Koethen grove, Brockton Ave., Riverside
H.E. Drobish, County Agent, Oroville CA
From progeny in 1924 nursery
From progeny in 1924 nursery.
East Highlands Orange Co.- Winn 58-7
Wetumpka Fruit Co., Lowell FL
USDA, Sacaton AZ
Santa Ana Mission, North Argentina
UCLA
Seedling from the Rubidoux Tract “Washington navel”
Ted Frolich, UCLA Variety Coll. R-1, T-6
Ted Frolich, UCLA
Cooper, Delta Lake TX
Shizuoka Prefecture, Japan (via W.P. Bitters, CRC)
Shizuoka pref., Shimizu-shi, Japan (via W.P. Bitters, CRC)
De Citricos De ICA Tulio, Ospina, Medellin, Colombia
Seedling of CRC #3276, 8A-12-39
Alfredo Ferrand, Peru
Budwood importation from Israel via Glenn Dale & CCPP
Seedling from 8A-5-21, CRC 1045
Guillermo Colon, Majorca, Baleric Is., SPAIN via Beltsville
Turkey, via W. Reuther
1910
1914
1914
1914
1914
1914
1914
1914
1914
1914
1916?
1916?
1917
1925
1927
1927
1931
1930
1932
1936
1940
1945?
1954
1915
1960
1960
1960
1960
1960
1961
1958
1960
1963
1963
1962
1967
1966
1966
1968
1968
1971?
1970
1978
1968
11. Blood orange
2561
3152
3242
3401
3596
3627
3650
3801
3811
3827
3828
3829
3830
3977
4000
4018
4032
Burris blood Valencia orange
Doble Fina blood orange (ops)
Vaccaro blood orange (ops)
Sanguine grosse ronde (ops)
Tarocco blood orange (ops) #7
Vaccaro blood orange (ops)
Entre Fina blood orange (ops)
Vainiglia Pink fleshed sweet orange
Moro blood orange
Ruby blood orange (ops)
Sanguinelli blood orange (ops)
Sanguinello a pignu (ops)
Moro blood orange (ops)
Washinton Sanguine (Doublefina Amelioree)
Sanguina Doble Fina
Tarocco blood orange
Bream Tarroco blood orange
384
442
272
413
265
362
521
510
544
576
1965
1960?
1965
1975
1987
1987
12. Other sweet orange and hybrid
0071
0245
0274
0281
0292
0321
0366
0371
0590
0591
0950
1045
1106
1512
1693
1696
2369
2373
2550
2602
2802
2856
3083
3182
3245
3246
3249
3251
3272
3347
3373
3403
3467
3476
3584
3599
3624
3625
3630
3632
3746
3754
3787
3802
Jaffa orange
Bessie sweet orange
Maltese oval sweet orange
Joppa late sweet orange
Homosassa sweet orange
Imperial variegated sweet orange
Star sweet orange
Orange of Heaven (Laranga de Ciel) (acidless orange)
Maltese Oval orange
St. Michael Paperrind sweet orange
Lima sweet orange (acidless)
Selecta sweet orange (Laranja selecta)
Koethen sweet orange
Bidwells Bar sweet orange seedling (Oroville sweet)
Bessie sweet orange seedling
Homosassa sweet orange seedling
East Highlands sweet orange
Dalandan sweet orange
Wetumpka sweet orange (ops)
Dillar sweet orange
Argentina sweet orange (ops)
Cadenera Fina sweet orange
Sathgudi sweet orange (ops)
Trovita strain A (Early sweet orange)
Capucin sweet orange
Cadena Punchosa sweet orange
Espagnole sans pepins sweet orange (ops)
Khailily (white) sweet orange
Berna sweet orange (ops)
Curry early sweet orange seedling
Precoce de Valence? (ops)
Aziza sweet orange (ops)
Citrus ujukitsu (ops)
Citrus shunkokan (ops)
Shamouti seedling (seedling of Sarah)
Perao orange #1 (ops)
Orange de Nice (ops)
Ovale orange (ops)
Biondo Riccio sweet orange (ops)
Cadenera orange (ops)
Shamouti orange, Israeli seedling #1
Selecta orange (ops)
Fuya Menuda sweet orange (ops)
Akcay Sekeri orange (Crescent)
428
116
284
316
394
51
Category
CRC
Other identifiers
VI
PI
Datef
244968
433933
539622
539623
539624
539625
539626
539627
539628
539629
539630
539631
539632
539633
539634
539635
539636
539637
244965
539638
539639
539640
539641
539642
539643
539644
539645
539646
539647
539832
539648
USDCS, Indio CA
Seedling from CRC 3555, old budline Indian River
Seedling of CRC 1414, old budline Catlin
USDCS, Indio CA
Seedling from CRC 2884, old budline Olivelands sweet
Seedling from CRC 2696, old budline Pera
Frank Russo, Sicily, via Glenn Dale & CCPP
Rotuma Island, via Capt. Polkinghorn & W. Reuther, CRC
Seed from Tahiti
Seed supplied by W.P. Bitters
John Carpenter, USDCS, Indio CA, via CCPP
Seed from USDCS 54-81, Indio CA
Brazil via John Carpenter & George Quesada, Novato CA
Seedling of PI 244965, an import from Spain
Import, country of origin not known.
PR China
PR China
PR China
PR China
PR China
PR China
PR China
PR China
PR China
Florida (brought back by D. Gumpf)
Jack Hearn, Orlando FL
1961
1979
1963
1958
1961
1967
1961
1960
1960
1962
1961
1961
1963
1964
1963
1966
1961
1984
1970
1975?
1985
1985
1985
1985
1985
1987
1987
1987
1987
1988
1989
539174
539175
539176
539681
31881
539237
539177
539159
539161
539162
539451
85728
539160
539680
539163
124169
539164
213224
539225
539348
539453
539677
539166
539450
539545
539181
539226
316538
316537
539227
539228
539229
539230
539231
Buds from hedge in rear of building of Old Station
Murphy Oil CO. nursery, Whittier CA
Murphy Oil CO. nursery, Whittier CA
C.C. Chapman grove, Fullerton CA
USDA, Chico Garden
Oroville CA
W.W. Youthers, USDA, Orlando FL
From progeny in 1924 nursery.
J.W. Porter grove near Hypoluxo, Palm Beach Co. FL
From CPB
Nabeuil, SE of Tunis, collected by Fawcett (No. 45)
Florida
USDA, Washington DC
Bonita CA
Fawcett #425, Bella Vista, Argentina
Faw. #363 Olivelands Jensen 6C-54-3
H.S. Gentry, Wandriker Farms, Poona, Mahhamaristra State (India?)
Ted Frolich, UCLA Blk D, R-28, T-1.
Hiroshi Yoshimura, Tanaka Inst., Univ. of Osaka, Japan
Ted Frolich, UCLA
12D-22-6, CRC
12D-22-15, CRC
Ted Frolich, UCLA
Hort. Res. Sta., Okitsu, Japan (via W.P. Bitters, CRC)
Hort. Res. Sta., Okitsu, Japan (via W.P. Bitters)
Joe Furr, USDCS, Indio CA (from Yuma AZ)
12. Other sweet orange and hybrid (cont.)
3807
3814
3858
3859
3860
3861
3862
3863
3864
3865
3866
3867
3868
3869
3870
3871
3873
3896
3898
3921
3933
3934
3935
3936
3937
3982
3983
3984
3985
3998
4002
Verna orange (ops)
Citrus sinensis (ops)
Pineapple sweet orange (ops)
Indian River sweet orange (ops)
Catlin sweet orange (ops)
Madam Vinous sweet orange (ops)
Hamlin orange (ops) (Norris)
Olivelands sweet orange (ops)
Pera orange (ops)
Marr’s Early sweet orange (ops)
Biondo Comune sweet orange (ops)
Rotuma Island sweet orange (ops)
Salustiana orange (ops)
Tahiti sweet orange (ops)
Finike sweet orange (ops)
Macetera sweet orange (ops)
Parson Brown sweet orange (ops)
Cipo orange (ops)
Blanca Macetera orange
Ovale o Calabrese orange
Citrus sinensis
Citrus sinensis
Citrus sinensis “:Jincheng”
Citrus sinensis “Xuegan”
Citrus sinensis “Xinhuicheng”
Xianfengcheng
Jincheng
Xuegan
Xinhuicheng
US 119 (Duncan gft ´ trifol.) ´ Succory sweet orange
Ambersweet orange
222
494
307
173
317
221
285
495
500
574
575
489
496
13. Sour orange and hybrid
0571
0622
0628
0656
0660
0693
0760
1588
1689
2192
2375-B
2438
2541
2588
2624
2715
2717
3059
3079
3225
3235
3257
3289
3290
3473
3565
3578
3607
3611
3681
3683
3684
3702
3703
Bouquet des Fleurs sour orange
Variegated sour orange
Standard sour orange
Daidai-double calyx sour orange
Paraguay bittersweet orange
Orogold sour orange hybrid (ops)
Citrus vulgaris (ops) (Japanese orange)
Orlando bittersweet orange seedling
Brazilian sour orange seedling
Stow #20 bittersweet orange (ops)
Chinotto orange
Tunisian sour orange (ops), Nabeul
Dummett bittersweet orange (ops)
Citrus taiwanica (Nansho daidai)
Keen sour orange #1-10
Granitos sour orange seedling, op, Argentina
Olivelands Sour orange
Citrus Kharna (ops)
Gabbuchinee (ops)
Citrus maderaspatana (ops) (Kichili)
Citrus natsudaidai (Kawano Strain) (ops)
Citrus sulcata (ops) (Sanbokan)
Citrus aurantium var. Salicifolia
Myrtifolia sour orange
Citrus rokugatsu (ops) (Rokugatsu-mikan)
Citrus canaliculata (ops) (Kikudaidai)
Pursha lime ´ Chinotto
Tosu (ops) (Citrus neo-aurantium)
Konejime (ops) (Citrus neo-aurantium)
(53-1-16 Clem ´ Hamlin) ´ Chinotto, F1
(53-1-16 Clem ´ Hamlin) ´ Chinotto F1
95
52
1914
1914
1914
1915
1915
1915
1916
1926
1927
1928
1930
1930
1932
1935
1936
1937
1954
1954
1959
1957
1960
1963
1962
1962
1966
1966
1968?
1968?
1968?
1968?
1968?
Category
CRC
Other identifiers
VI
PI
Datef
539232
539233
539234
539235
539236
539167
539168
539169
539452
539170
539171
539172
539173
Joe Furr, USDCS, Indio CA (Furr’s Salt plot)
Seedling from CRC 711, old budline Rubidoux sour
Seedling budline from CRC 1589, old budline Seville
Seedling of CRC 2375, old budline Chinotto
PR China
PR China
PR China
1968?
1968?
1968?
1968?
1968?
1970
1961
1961
1961
1985
1985
1987
1981
539386
539407
539408
600632
539409
539352
46132
46121
539353
539354
539355
539356
539357
539358
539359
539360
539361
539362
539363
539364
539365
539366
539367
539369
539370
539371
539372
539373
Webber’s #16, from Mr. Damon, Moanalua Gardens, Honolulu
Rubidoux Tract variety block – buds from tree 1187
USDA Plant Introduction Garden, Chico
P.J. Wester, Lamao Bataan, Phillipine Islands
George C. Roeding’s nursery
Ichang, Hupeh, China
Frank N. Meyer, FHB #23783, Hupeh, China
American Consul, Changsha, China- FHB #15097
Sunshine Ranch, San Fernando CA
From CPB
From CPB
Siam (via CPB)
Siam (via CPB)
From CPB
From CPB
From CPB
From CPB
Siam (via CPB)
From CPB
From CPB
From CPB
From CPB
From CPB
From CPB
From CPB
Siam (via CPB)
From CPB
From CPB
From CPB
From CPB
From CPB
From CPB
From CPB
From CPB
Suriname, South America?
USDA, Washington DC
F. Heiney, Brawley CA
Source: Robinson
Ed Pollock, Molong Road, N.S.W. Australia
H. Yoshimura, Univ. of Osaka, Japan
CRC 11B-5-4, A hybrid of Siamese Pink ´ Siamese Sweet
prod. at CRC, Riverside
Dept. Agr, Stock & Fisheries, Port Moresby, Papua New Guinea
Hawaii, via CCPP
Import from Hawaii (Special permit from Sacramento
Import from Hawaii (Special permit from Sacramento)
Glenn Dale Quarantine Facility, import from Japan
Import from Japan
Import from Japan
13. Sour orange and hybrid (cont.)
3705
3706
3709
3712
3715
3728
3855
3856
3857
3929
3930
3981
4004
Chinotto hybrid
Rubidoux sour orange (ops)
Seville sour orange
Chinotto sour orange (ops)
Citrus aurantium “Goutoucheng” (Leather-head sour)
Citrus aurantium “Zhuluan”
Zhuluan
Gou Tou sour orange (Leather-head sour) (Goutoucheng)
427
554
14. Pummelo (shaddock)
0302
0448
0578
0640
0644
1208
1212
1224
1225
2236
2240
2241
2242
2243
2244
2245
2246
2248
2249
2338
2340
2341
2342
2346
2347
2348
2349
2350
2351
2352
2353
2355
2356
2421
2453
2487
2583
2596
2752
3067
3148
3224
Tresca “grapefruit” pummelo
Moanalua pummelo
Fleming’s shaddock
Siamese pummelo
Philipine pummelo (ops)
Roeding’s Pink pummelo
Chinese pummelo
Chinese pummelo
Hunan pummelo (ops)
Sunshine pummelo
Siamese pummelo (acidless) (aka Siamese Sweet)
Unnamed pummelo (Siam)
Kao Panne pummelo (Kao Pan)
Pink pummelo (Java)
Red pummelo (Java)
Pink pummelo
Unnamed pummelo
Kao Panne pummelo
Red Fleshed pummelo
Citrus grandis- Unnamed
Karn Lau Yau pummelo
Pong Yau pummelo
African pummelo
Deep red pummelo
Pin Shan Kong Yau pummelo
Kao Ruan Tia pummelo
Kau Ruan Tia pummelo
Kao Phuang pummelo
Nakon Chaisi pummelo
Unnamed pummelo, Siam
Kao Panne pummelo, Siam
Siamese pummelo
Citrus grandis- Unnamed
Alemoen pummelo (ops)
Tau Yau pummelo
Arajon pummelo
PanDan Pummelo
Sweet pummelo (ops)
Citrus sino-grandis (ops) (Otomikan)
Chandler pink pummelo
3282
3805
3806
3926
3927
3928
3940
3944
3945
Citrus grandis? (unknown) (ops)- New Guinea
Reinking pummelo
Tahitian pummelo
Kao Phuang pummelo
Thong Dee pummelo
Itoshima Bankan
Haiku B pummelo
Kawachi-bankan pummelo
Mato Buntan (Mato) pummelo
159
443
161
160
11
539375
539376
539377
539378
539379
539380
97930
539382
539383
539385
539388
539669
539389
274
342
446
447
448
449
453
454
539390
539391
539392
539393
539394
539395
539369
539397
539398
53
1914
1914
1914
1915
1915
1919
1919
1919
1919
1930?
1930
1929?
1930
1930
1929/30
1929
1930
1930
1930
1930
1930
1930
1930
1930
1930
1930
1930
1930
1930
1930
1930
1930
1930
1930
1932
1935
1935
1938?
1954
1956
1959
1956
1965
1971
1984
1984
1984
1984
1984
1984
Category
CRC
Other identifiers
VI
PI
Datef
14. Pummelo (shaddock) (cont.)
3947
3948
3949
3950
3951
3959
3961
3978
3979
4027
4028
Suisho Buntan (Suisho) pummelo
Kao Pan pummelo
Pauthel pummelo
Banokan
Hirado Buntan (Hirado) pummelo
Egami Buntan (Egami, Ogami) pummelo
Banpeiyu (Pai You from Taiwan) pummelo
Kinokawa Buntan
Anseikan
US 145 Thong Dee pummelo
Rubidoux pummelo
456
457
458
459
467
477
478
522
479
569
570
539399
539400
539401
539402
539403
539404
539405
539406
539673
600670
600663
Import from Japan
Import from Japan
Import from Japan
Import from Japan
Improt from Japan
Japan
Japan
Florida
1984
1984
1984
1983
1983
1985
1985
1987
1987
539224
539691
539410
539411
539412
539368
539384
539387
539682
539165
539201
539686
539458
539459
539218
539219
214012
539221
539200
539150
539199
539222
539223
600667
F. M. Reed, Riverside CA
W.T. Swingle, USDA
W.T. Swingle, USDA
N/A
From CPB
USDA, Torrey Pines Station CA
Ed Pollock, Molong Road, N.S.W., Australia
J.R. Creech, Kurume, Kyushu, Japan
Dept. of Agric., Lyallpur, India
Ted Frolich, UCLA
Shizuoka Prefecture, Japan (via W.P. Bitters (CRC))
Shizuoka Prefecture, Japan (via W.P. Bitters, CRC)
Yuma Mesa Citrus Exp. Station, Yuma AZ
Hybrid developed at CRC, original code: 11C-38-4
India via Plant Intro. Station, Glenn Dale MD
Joe Furr, USDCS. Indio CA. ?
Japan
South Africa
1910
1914
1924
1924
1927
1930
1936
1954
1955
1954
1960
1963
1963
1963
1964
1966
1954
1974
1983
1983
1983
1984
1984
539465
539469
539475
539488
539460
539461
539462
539463
539466
539467
539468
539470
539471
539472
539473
539474
539476
539477
539478
539479
539480
539481
539482
433294
433293
539483
539484
539485
George Roeding Nurseries
Dixon Ranch
Mr. Jochimsen, Baseline Ave., La Verne FL
Texas
New Zealand
Hall Orchard, Upland CA
J.F. Reed, Taft CA
12C-15-1, CRC (Shoot from root)
H.B. Frost nucellar seedling
D.J. Nicholson, Orlando FL
Seedling of CRC #2014, 8A-2-29
USDCS, Indio CA via CCPP
Limb sport of Marsh, found at Yuma AZ
Whitney Ranch, Oasis CA, via CCPP
Willits & Newcomb, Thermal CA
Florida, via W. Reuther, UCR
Hawaii, via Glenn Dale & CCPP
Hawaii, via Glenn Dale & CCPP
Texas
Texas – see note on CRC 3914 card.
Texas – see note on CRC 3914 card.
1914
1914
1914
1914
1919
1925
1930
1930
1942
15. Pummelo hybrid
0042
0579
1462
1481
1775
2343
2608
3066
3092
3133
3275
3464
3465
3470
3488
3555
3556
3781
3904
3905
3907
3941
3942
4026
4029
Shaddock x St. Michael or. seedling
Moli Kurikuri (Citrus grandis ´ C. macroptera?) (Citrus vitiensis?)
Cuban shaddock
Lemelo
Lemon shaddock seedling (Lemelo)
Philippine pummelo hybrid
Red Aranyan pummelo
Sour pummelo (ops)
Citrus tamurana (ops) (Hyuganatsu) (New Summer or.)
Gadadehi (Pummelo or pummelo hybrid?)
Citrus hiroshimana (ops) (Natsuzabon) hybrid
Citrus tengu (ops) (Shigetomi, Kinkunebu)
Citrus obovoidea (ops) (Marumero, Kinkoji)
Citrus otachibana (ops) (large tachibana)
Yuma Ponderosa “lemon”
Frua mandarin x low acid pummelo hybrid (Cocktail grapefruit)
Citrus rugulosa (Attani)
Tahitian pummelo ´ Star Ruby grapefruit
Citrus hiroshimana (Natsuzabon)
Asahikan
Hassaku (Citrus hassaku, Beni Hassaku)
Puma hybrid (Pummelo ´ grapefruit)
Hassaku
Pomlit pummelo hybrid (Djeroek Deleema Kopjor)
Unnamed grapefruit/pummelo hybrid
410
127
431
432
434
450
451
566
571
16. Grapefruit
0248
0297
0343
0596
1198
1565
2010
2014
2784
2850
2885
3068
3128
3139
3184
3398
3637
3638
3770
3774
3804
3831
3832
3883
3886
3914
3915
3916
Royal grapefruit
Triumph grapefruit
Grapefruit seedling
Imperial grapefruit
Foster Pink grapefruit
Marsh seedy grapefruit
Marsh pink grapefruit
Cecily grapefruit
Jochimsen grapefruit (ops)
Redblush grapefruit (ops) #3
Wheeny grapefruit
Hall grapefruit
Reed Marsh grapefruit (ops)
Camulos grapefruit
Frost nucellar Marsh grapefruit
Nicholson “navel” grapefruit (ops)
Cecily grapefruit (ops)
Hudson Foster grapefruit (ops)
Star Ruby grapefruit
“Genetic Dwarf” grapefruit
Whitney Marsh grapefruit, old budline
Shambar grapefruit (ops)
Duncan grapefruit
Perlis #2 grapefruit
Perlis #1 grapefruit
Henderson Ruby grapefruit
Ray Ruby grapefruit
Rio Red Grapefruit
245
31
142
29
308
355
361
148
269
398
401
465
466
440
54
1943
1955
1958
1957
1915?
1960
1966
1968
1977
1977
1961
1965
1962?
1979
1979
1985
1985
1985
Category
CRC
Other identifiers
VI
PI
Datef
470
539486
539487
CRC Breeding project- Field 6E, Stand 25, tree 3
1987
1988
309
323
354
436
511
539464
539202
539203
372058
539489
539490
From CPB
Hybrid developed at CRC, original source: 6C-26-20
Hybrid produced at CRC, original designation: 6C-26-18
Import from New Zealand, via Glenn Dale & CCPP (budwood)
Puerto Rico via Glenn Dale (request, W.P. Bitters)
South Africa
1930
1968
1975
1977
1983
1985
38388
539713
539254
213349
539198
539255
539448
539196
539672
539197
From CPB
Ted Frolich, UCLA
H.S. Gentry, Chettalli, Coorg State, India
Phil Reece, Orlavista Field Sta., Orlando FL
Malaysia, via R. Scora, CRC
Prof. Tsuin Shen, Peking Agric. Univ., Peking, PR China
BOH Plantation, Fairley Estates, Cameron Highlands, West Malaysia
1930
1956
1958
1954
1963
1963
1962
1971
1980
1985
539250
539449
45534
45945
P.J. Wester, Philippine Islands
Frank N. Meyer, FHB #23067, PR China
Frank N. Meyer, FHB #23721 & 23942, PR China,
in Hubei Prov. along Yangtze river.
Frank N. Meyer, FHB #23790, PR China
W.T. Swingle, USDA
W.T. Swingle, USDA
From CPB
From CPB
PR China (via CPB)
From CPB
F.E. Gardner, Orlando FL
Khasi Hills, Assam, India
Rupchand, Mawknland via Schillang, Assam, India
Punjab Agr. College, Lyallpur, Pakistan
Fruit Exp. Sta., Shillong, India
College of Agric., College, Laguna, Philippines
Phil. Coll. of Agric., Los Banos, Philippine Islands
Dick Hamilton, University of Hawaii
Dick Hamilton, Hawaii
Willits & Newcomb, Thermal CA, via CCPP
PR China
Japan
Dick Hamilton, Hawaii
1914
1916
1919
1919
Hale’s ranch, Santa Barbara CA
USDA
W.T. Swingle, USDA
W.T. Swingle, USDA
Joe Furr, USDCS, Indio CA. From Yuma NF
W.B. Chapman, League City TX
Bruce Bartholomew, Berkeley Botanic Garden, CA
1912
1916?
1924
1924
1957
1958
1957
1960
1963
1968
1972
1975
1978
1979
1967
16. Grapefruit (cont.)
3968 Tetraploid grapefruit
3993 Flame grapefruit seedling [800-1-26-71]
17. Grapefruit hybrid
2381
3602
3764
3769
3909
3962
Poorman orange (Cudebeck strain) (New Zealand gft.)
Oroblanco grapefruit hybrid (Patented by U.C.)
Melogold (UC patented hybrid)
New Zealand grapefruit (Poorman orange)
Chironja
Rex Union
18. Miscellaneous Citrus species
2434
3146
3163
3175
3469
3474
3574
3780
3797
3900
Citrus pennivesiculata (C. moi, Gajanimma)
Citrus yuko (ops)
Citrus indica (ops) (hybrid)
Citrus species (ops)
Citrus hanayu (ops)
Citrus intermedia (ops) (Yamamikan)
Citrus miaray (ops)
Citrus halimii
Citrus hongheensis (ops) (Honghe papeda)
Citrus halimii
19. Citrus subgenus Papeda and hybrid
0432
0767
1215
1216
Citrus hystrix, Cabuyao
Citrus webberii var. Montana (Weeping Philippine hybrid) (ops)
Ichang lemon (ops) (Shangyuan)
Citrus junos (Yuzu or Kansu)
1219
1455
1456
2316
2320
2327
2427
2431
2454
2892
3052
3056
3103
3203
3471
3605
3612
3765
3793
3842
3931
3943
4016
Ichang lemon seedling
Citrus webberii (Kalpi, Nogapog) (cutting A)
Citrus webberii (Kalpi, Nogapog) (cutting A)
Citrus excelsa
Citrus longispina (Talamisan) (probably not C. longispina)
Citrus ichangensis
Davao lemon (Citrus davoensis)
Citrus ichangensis
Citrus hystrix
Citrus excelsa?, Philippines
Citrus latipes (ops) (Khasi papeda)
Citrus species (ops) (Papeda type)
Citrus hystrix
Soh niangrang (ops)?
Citrus sudachi (ops)
Samuyao (microcarpa (ops))
Kulobot (ops) (Papeda hybrid)
Citrus excelsa
Unknown species of papeda
Citrus macrophylla seedling
Citrus ichangensis
Kabosu
Unknown species of papeda (papeda hybrid)
187
313
452
46128
539692
539693
539192
539346
539251
539187
539252
539248
539194
230987
214467
539249
254733
539676
539694
539217
539670
539671
539182
539253
539674
1919
1924
1930
1930
1930
1930
1930
1930
1947
1954
1954
1955
1959
1963
1967
1966
1972
1978
1968
1985
1984
1978
20. Kumquat and hybrid
0132
1044
1440
1471
3237
3259
3295
3360
3475
3642
3759
3789
3790
3818
3833
Nagami kumquat
unnamed-probably a kumquat hybrid
Thomasville citrangequat
Meiwa kumquat seedling (F. crassifolia)
Fortumella japonica (ops) (Marumi, Maru-kinkan)
Citrangequat 19-15-7
Procimequat?
Nippon orangequat seedling
Fortunella obovata (ops) (Fukushu kumquat, Chojukinkan)
Sinton citrangequat (ops)
Nagami cross (with Dancy?) AKA: Indio mandarinquat
Fortunella hindsii
Fortunella hindsii
Fortunella crassifolia (Meiwa)
Meiwa kumquat (ops)
355?
306
539728
539725
539849
539721
539727
539851
539805
149453
539730
539853
539726
539723
539724
433934
539722
55
Category
CRC
Other identifiers
VI
PI
Datef
20. Kumquat and hybrid (cont.)
3877 Nagami kumquat
3901 Fortunella polyandra
276
539729
539731
John Carpenter’s yard, Indio CA, via CCPP
Botanic Garden, Univ. of Kuala Lumpur, Malaysia
1965
1985
83
539791
539750
539751
539572
539573
539755
539756
240121
539757
539758
539759
539760
539761
539762
539763
539764
539765
539766
539767
539768
539769
539770
539771
539773
539774
539775
539776
539777
539778
539779
539780
539781
539782
539783
539784
539785
539786
539671
539788
433262
433263
539789
539790
600647
600648
600649
600650
600657
Rubidoux Experiment Station
W.T. Swingle, USDA
Pomeroy’s
Experiment Station, Gainesville FL
L.B. Barnes grove, Gainesville FL
E. Mortensen, Winter Haven TX
Dept. Agr. Sydney, N.S.W. Australia
Joe Furr, USDCS, Indio CA from Yuma AZ
Domingo Hardison, Santa Paula CA
Domingo Hardison, Santa Paula CA
L. Jacobson Ranch, Placentia CA
Yamaguchi grove, Ontario CA
SCFS Bl. 24, R-23, T-3
SCFS Bl. 24, R-20, T-6
SCFS Blk 24, R-21 T-2
SCFS 24-23-12
SCFS 24-20-25
SCFS 24-23-24
SCFS 24-20-22
SCFS 24-21-24
SCFS 24-20-14
SCFS 24-21-5
SCFS 24-22-3
SCFS 24-23-11
Iwamassa, Saga, 840, Japan
English Ranch, Lindsay CA
PR China
PR China
Hunan Horticultural Institute, PR China
Guandong, PR China
PR China
1916
1924
1927
1932
1932
539812
539813
539814
13002
539833
539834
539835
539809
539836
539837
539838
539822
539810
W.T. Swingle, USDA
W.T. Swingle, USDA
W.T. Swingle, USDA
W.T. Swingle, USDA
W.T. Swingle, USDA
W.T. Swingle, USDA
W.T. Swingle, USDA
W.T. Swingle, USDA
W.T. Swingle, USDA
1914
1914
1914
1914
1924
1924
1924
1924
1924
1924
1924
1924
1924
21. Trifoliate
0838
1498
1717
2552
2554
2861
2862
3151
3206
3207
3209
3210
3211
3212
3213
3215
3217
3218
3219
3330-A
3330-B
3338
3345
3411
3412
3484
3485
3486
3547
3548
3549
3570
3571
3572
3586
3587
3588
3795
3876
3882
3888
3938
3939
4006
4007
4008
4009
4017
Rubidoux trifoliate orange
USDA trifoliate ( lf )
Pomeroy trifoliate seedling (lf)
Webber-Fawcett #22 trifoliate orange seedling
Barnes trifoliate orange seedling (sf)
Texas trifoliate (ops) (sf)
Florida trifoliate (ops)
Australian trifoliate (ops)
Argentina trifoliate (lf)
Towne G trifoliate (lf)
Rich 12-2 trifoliate (lf)
Kryder 16-6 trifoliate
Rich 22-2 trifoliate (sf)
Kryder medium trifoliate (lf)
Kryder 60-2 trifoliate (lf)
Kryder 55-5 trifoliate
Flying Dragon trifoliate (ops) (Poncirus trifoliata var. Monstrosa)
Flying Dragon trifoliate variant (ops) (Poncirus trifoliata var. Monstrosa)
Benecke (Beneckie) trifoliate (ops) (lf)
Christiansen trifoliate (ops) (lf)
Jacobson trifoliate (ops) (sf)
Yamaguchi trifoliate (ops) (lf)
Frost tetraploid 4x trifoliate
Rich 16-6 trifoliate
Benoit trifoliate orange
English large trifoliate orange (sf)
Simmons trifoliate seedling
Ronnse trifoliate (sf)
Taylor trifoliate (sf)
Towne “F” trifoliate (lf)
Rich 7-5 trifoliate (lf)
Marks trifoliate
Hiryo (Flying Dragon trifoliate)
English Dwarf trifoliate (ops)
Poncirus trifoliata var. Hiryo (Flying Dragon)
Monoembryonic Poncirus trifoliata
Poncirus trifoliata #27
Poncirus trifoliata #26 “Nanjing”
“Big-leaf” trifoliate
“Little-leaf” trifoliate
“Little-leaf” trifoliate
Trifoliate (open pollinated)
Small Leaf trifoliate
84
164
383
397
403
541
1957
1958
1958
1958
1958
1958
1958
1958
1958
1958
1958
1958
1958
1958
1958
1958
1961
1961
1965
1965
1965
1965
1965
1965
1965
1965
1965
1965
1965
1965
1978
1958
1979
1979
1985
1985
1989
1989
1989
1989
1990
22. Trifoliate hybrid
0271
0275
0276
0301
1436
1437
1438
1441
1447
1448
1449
1452
1459
Cunningham citrange
Savage citrange
Sanford citrange
Rusk citrange
Citradia hybrid (cutting A)
Rusk citrange
Citrangor seedling
Citremon
Citremon (cutting B)
Citrumelo seedling
Troyer citrange (Citruvel) seedling
249
233
150
105
86,88
56
Category
CRC
Other identifiers
VI
PI
Datef
22. Trifoliate hybrid (cont.)
1463
2618
2748
2863
2865
2866
3205
3336
3337
3341
3348
3351
3414
3415
3417
3552
3566
3573
3767
3771
3821
3881
3889
3908
3911
3912
3954
3957
3969
4025
Morton citrange
Citrandarin (Trifoliate ´ mandarin)
Morton citrange
Carrizo citrange (ops)
Uvalde citrange
Citrange #1416 (ops)
Yuma citrange
Spanish sweet orange ´ Poncirus trifoliata seedling
Sacaton citrumelo seedling
Citrumelo, CPB 4475? (Swingle?)
Citrumelo
Fairhope trifoliate seedling
Sacaton citrumelo (ops)
Citranguma (ops) (S-302)
Sacaton citrumelo (ops)
Citrangelo seedling (S-281)
Microcitrus ´ trifoliate or.
Glen citrangedin (ops) (Altamaha)
Swingle (?) citrumelo
Swingle citrumelo
Citrumelo (Hall grapefruit ´ trifoliate)
Poncirus trifoliata x Satsuma (citrondarin)
Hall gft. x Rubidoux trifoliate (Code C-190)
Benton citrange
C-32 citrange
C-35 citrange
Minneola ´ trifoliate (MXT or Trifeola)
Cleopatra mandarin ´ trifoliate (X639)
African shaddock ´ Rubidoux trifoliate
Hamlin + Flying Dragon
97
143
356
396
435
287
293
468
469
476
533
539811
539839
539754
150916
150917
539815
539816
539817
539823
539824
539825
539772
539826
539841
539827
539842
539854
539843
539844
539828
539845
433930
539829
539819
539820
539821
539846
539847
539830
600676
W.T. Swingle, USDA
USDA, Sacaton AZ
CPB?
Plant Introduction
Plant Introduction
W.C. Cooper, Weslaco TX
Joe Furr, USDCS, Indio CA. Originally from Yuma AZ
Albert Newcomb Ranch, Thermal CA
Albert Newcomb Ranch, Thermal CA
Ted Frolich, UCLA
Del Rio Farms, Weslaco TX
Albert Newcomb, Thermal CA
Texas sub-station #19, Winter Haven TX
A. Newcomb Ranch, Thermal CA
Domingo Hardison, La Campana Ranch Fillmore CA
W.C. Cooper, 2120 Camden Rd., Orlando FL
USDCS, Indio CA via CCPP
Hybrid seedling produced at CRC
Russia via Glenn Dale & CCPP
Australia via Glenn Dale (request by W.P. Bitters)
CRC 11C-80-7 (trif. ´ Ruby orange)
CRC 8C-15-7 (trif. ´ Ruby orange)
USDCS
1924
1936
1940
1945?
1943
1947
1958
1962
1962
1961
1961
1960
1962
1962
1962
1962
1966
1962
1975
1977
1978?
1979
1983
1983
52801
539145
539716
539855
539734
539740
539793
539794
539795
539796
539797
539746
539801
539143
539748
539808
231073
231240
539142
539745
235419
539747
263640
127866
246335
539144
231241
247137
539149
266043
236991
539717
539800
600674
109758
George Walder, Dir. of Agric., Sydney, NSW, Australia
W.T. Swingle, USDA (cutting A)
W.T. Swingle, USDA
W.T. Swingle, USDA
W.T. Swingle, USDA
W.T. Swingle, USDA
W.T. Swingle, USDA
W.T. Swingle, USDA
W.T. Swingle, USDA
W.T. Swingle, USDA
W.T. Swingle, USDA
W.T. Swingle, Date Garden, Indio CA
From CPB to Indio
Ted Frolich, UCLA
Charles Knowlton, Fullerton CA
Bill Stewart, Arboretum, PasadenaCA
Ed Pollock, Malong Rd., Parkes N.S.W., Australia
Hort. Dept., Hawaii Agr. Exp. Station
Harold Winters, Beltsville MD
USDA Plant Introd. Station, Glenn Dale, MD
Yangambi State of INEAC, Belgium
H. Chapot, Ravat, Morocco
G.R. Bates, Causeway, Salisbury, Rhodesia
Dept. of Agric., Port Moresby, Papua New Guinea
E. Pollock, Parkes, N.S.W., Australia
Henry Nakasone, Univ. of Hawaii
Oscar Clark, CRC
U.S. Plant Introd. Garden, Glenn Dale MD
1921?
1924
1924
1924
1985
1985
1988
23. Miscellaneous species, not genus Citrus
1260
1430
1460
1466
1484
1485
1491
1492
1494
1495
1497
1637
2439
2878
2879
2891
3117
3126
3140
3165
3166
3171
3284
3285
3286
3287
3288
3294
3296
3298
3299
3463
3507
3508
3509
Geijera parviflora
Atlantia citroides
Clausena lansium seedling (Wampee)
Faustrimedin (Microcitrus australasica ´ Calamondin)
Microcitrus australasica var. sanguinea seedling (Finger lime)
Microcitrus virgata seedling (Sydney hybrid)
Severinia buxifolia (Chinese box orange)- cutting A
Severinia buxifolia (nearly spineless)- cuttings E & F
Severinia buxifolia seedling
Severinia buxifolia seedling
Severinia buxifolia (brachytic) seedling
Murraya paniculata (Orange Jessamine)
Eremocitrus glauca hybrid
Aeglopsis chevalieri seedling
Hesperethusa crenulata
Faustrime
Pleiospermium species (ops)
Citropsis schweinfurthii (ops)
Aegle marmelos (ops) (Bael fruit)
Murraya koenigii seedling
Clausena excavata (ops)
Murraya paniculata (ops) (Hawaiian Mock orange)
Clymenia polyandra (ops)
Glycosmis pentaphylla (ops)
Citropsis gabunensis (ops)
Atalantia ceylanica (ops)
Swinglea glutinosa (ops)
Citropsis daweana (ops)
Citropsis gilletiana (ops)
Microcitrus warburgiana (ops)
Feronia limonia (Wood Apple)
Eremocitrus glauca
Triphasia trifolia
Ruta graveolens
Paramygnia scandens (?)
57
1924
1924
1924
1924
1924
1924
1926
1930
1950
1950?
1948?
1957
1956
1954
1956
1955
1960
1960
1958
1957
1956
1958
1960
1960
1957
1962
1956
1961
1965
Category
CRC
Other identifiers
VI
PI
Datef
23. Miscellaneous species, not genus Citrus (cont.)
3510 Feroniella oblata (ops)
539720 Agric. Exp. Sta., Rio Piedros, Puerto Rico
3511 Pamburus missionis
539749 U.S. Plant Introduction Station, Miami FL
3514 Balsamocitrus daweii
539147 Prof. K. Mendel, Volcani Institute Rehovoth, Israel
3517 Calodendron capense (Cape Chestnut)
Wishing Well Nursery, Riverside
3538 Esenbeckia runyoni
Dave Dryer, Fruit & Veg. Lab., Pasadena CA
3661 Microcitrus australasica
306115 Joe Furr, USDCS, Indio CA (from Yuma AZ)
3663 Microcitrus australis
539736
3724 Severinia buxifolia
539798 Republic of China
3725 Atalantia zeylanica
539146 Royal Botanic Gardens, Peradeniya, Ceylon
3726 Severinia buxifolia?
539799 Royal Botanic Gardens, Peradeniya, Ceylon
3782 Microcitrus warburgiana
539743 D.J. Hutchinson, Orlando FL
3784 Microcitrus inodora
539741 D.J. Hutchinson, Orlando FL
3785 Microcitrus inodora
539742 New Guinea via John Carpenter, USDCS, Indio CA
3786 Merrillia caloxylon
539733
3788 Clausena anisata
358849 Ag. Tech. Serv., Pretoria, South Africa, via Plant Intro Office
3800 Atalantia monophylla
109613 China, via Glenn Dale & CCPP
3824 Esenbeckia hartmanii
3899 Clausena excavata
539715 Lohan, Sabah, Borneo, via R. Scora
3902 Micromelum minutum
539744 Kampong (Village), Takutan, Sabah, Borneo
3917 Clymenia ´ Procimequat
539848 Hybrid produced at UCR
3918 Hardshelled Citrus relative
539732
3966 Wenzelia dolichophylla
277411 New Guinea via Glenn Dale
3967 Clausena lansium,“Kai Sum Wampee”
296321 Glenn Dale Quarantine Facility
4033 Afraegle paniculata
607466
4034 Clausena hardmandiana
4035 Glycosmis perakensis
4036 Severinia disticha
607467
a
The CRC (Citrus Research Center) number is the identification number used for CVC purposes.
b
(ops)=open pollinated seedling.
c
A VI (Virus Introduction) index number is assigned to an accession by the CCPP after it has been cleaned.
d
The PI (Plant Introduction) number is assigned by the US NPGS for items it has accessioned.
e
Source of accession, intermediary, and origin, if known. Glenn Dale is the location in Maryland of a USDA quarantine facility. Abbreviations used: CPB=Crop Plant Breeding-USDA.
f
Date the accession was received by the CVC.
58
1964
1964
1966
1965
1967
1968?
1968?
1968?
1968?
1968?
1968?
1968?
1968?
1968?
1968?
1968?
1967
1967
1967
1976
1976
1977
1969?
1977
1960
1985
1985
1966?
1983
1983
59
60

Citrus Genetic Resources in California

Transcription

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