karyomorphology and chromosome number confirmation in uraria

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Datta K. Animesh et al. IRJP 2012, 3 (7)
INTERNATIONAL RESEARCH JOURNAL OF PHARMACY
www.irjponline.com
Research Article
ISSN 2230 – 8407
KARYOMORPHOLOGY AND CHROMOSOME NUMBER CONFIRMATION IN
URARIA PICTA (JACQ.) DC.
Bhattacharya Arnab and Datta K. Animesh*
Department of Botany, Cytogenetics and Plant Breeding Section, University of Kalyani, Kalyani – 741235, West Bengal, India
Article Received on: 10/04/12 Revised on: 23/05/12 Approved for publication: 16/06/12
*Dr. Animesh K. Datta, Professor, Department of Botany, Cytogenetics and Plant Breeding Section, University of Kalyani, Kalyani – 741235, West Bengal,
India Email: [email protected]
ABSTRACT
Karyomorphological studies performed in Uraria picta (Jacq.) DC. (Family: Leguminosae, Subfamily: Papillionidae), an important Ayurvedic herb
(Ayurvedic name: Prishni parni), revealed 7 (2n = 22; 2Lsm + 2Lscsm + 4Mm + 2Msac + 2Ssm + 8Sm + 2Sac) morphologically distinct chromosome types. The
chromosomes in the species were graded (long: L - ≥ 2.0µm; medium: M - ≥ 1.0µm; small: S - < 1.0µm) on the basis of absolute chromosome length (0.59µm
to 2.625µm). The karyotype showed preponderance of chromosomes with metacentric (m) primary constrictions; although, it was asymmetric in nature (TF%:
37.65). Total haploid chromosome length was noted to be 12.63µm ± 3.73. Two pairs of chromosomes in the complement were with secondary constrictions
and they were associated both with short as well as long arms. The chromosome number (2n = 22) analyzed in root tip mitosis was in agreement to the number
noted in microsporocytes (n = 11). The confirmed number in the species is 2n = 22.
KEYWORDS: Uraria picta, Karyomorphology, meiotic analysis chromosome number confirmation.
INTRODUCTION
Uraria picta (Jacq.) DC. (Family: Leguminosae; Subfamily:
Papillionidae) is an important herb (also reported to be a
woody herb1, a perennial herb2-3 and a shrub4) in Ayurvedic
(Ayurvedic name: Prishni parni) medicine (used parts:
roots/leaves/whole plant)5-8. The chromosome number is
reported to be variable (n = 11 4, 9-11; 2n = 1612; 2n = 20 in the
genus Uraria13) in the species; although, chromosome
number alone does not provide any cytogenetical information
which may be used to design breeding strategies for crop
improvement. The present communication reports on the
karyomorphology of U. picta, which is previously
undescribed, with an objective to collect cytological
information for efficient breeding. The chromosome number
recorded in root tip mitosis was also confirmed from meiotic
preparations. Although, cytological studies are rather meager
in Ayurvedic plant species14-16, they often carry a wealth of
information for breeders, geneticists and other researchers.
MATERIALS AND METHODS
Root tips (generated from pre-soaked petri plate germinated
seeds of Uraria picta; seed samples were collected from
Medicinal Plant Garden, Narendrapur, Ramkrishna Mission,
Govt. of West Bengal) of about 2.0 to 3.0mm length were
pretreated in 0.1% colchicine for 3 hours 30 mins (room
temperature – 33.0°C ± 1.0°C) washed in distilled water and
kept in 0.01M KCl: 0.005M NaCl mixture (3:1) for overnight
before fixing in 70.0% alchohol and storage under
refrigeration. The root tips were stained in 4.0% aceto-orcein:
4N HCl mixture (9:2) for 2 hours and finally squashed in
45.0% acetic acid and observed under the microscope.
Suitable metaphase plates (3 properly and uniformly
condensed) were scored and measurements of the
chromosomes were taken from camera lucida drawings at the
magnification of 20×100x.
The centromeric nature in the chromosomes were classified
as metacentric (m), sub-metacentric (sm), sub-acrocentric
(sac) and acrocentric (ac) in accordance to Hirahara and
Tatuno17. On the basis of chromosome length (long: L - ≥
2.0µm; medium: M - ≥ 1.0µm; small: S - < 1.0µm),
centromeric position and the presence of secondary
constriction (sc), the chromosomes were morphologically
graded: type A: long metacentric chromosomes with
secondary constrictions associated to short arm, type A1: long
sub-metacentric chromosomes with satellites and it is with
long arm, type B: medium sized chromosomes possessing
metacentric primary constrictions, type C: medium sized
chromosomes with sub-acrocentric primary constrictions,
type D: small sub-metacentric chromosome, type E: small
metacentric chromosomes and type F: small chromosomes
with acrocentric primary constrictions. Total haploid
chromatin length, TF% (proportion of short arm in the total
chromatin length) and S% (relative length of shortest
chromosomes compared to the longest) were also analyzed.
Karyomorphological data was used to compute karyotype
formula.
Meiotic chromosome preparations were made as was
suggested by Bhattacharya and Datta11, 18. Microphotographs
for both mitotic and meiotic chromosomes were taken from
temporary squash preparations and subsequently magnified.
RESULTS AND DISCUSSION
Karyomorphological studies revealed 7 (2n = 22; 2Lsm +
2Lscsm + 4Mm + 2Msac + 2Ssm + 8Sm + 2Sac) morphologically
distinct chromosome types (Table 1, Fig 1.A-B). The
karyotype showed prevalence of chromosomes (14 out of 22)
with metacentric primary constrictions (F%: 40.27 to 48.47);
although, 4 chromosomes with sub-metacentric (F%: 32.62 to
37.84), 2 with sub-acrocentric (F%: 23.08) and 2 with
acrocentric (F%: 15.25) constrictions were also present.
Absolute chromosome length in the complement ranged from
0.59µm to 2.625µm. Two pairs of long chromosomes
(2.08µm to 2.625µm) were with satellites and the satellites
were associated with both the short arm (type A1) as well as
long arm (type A) of the chromosomes. Total haploid length
and S% in the species were 12.63µm ± 3.73 and 22.48
respectively. The karyotype was asymmetric in nature as
evident from TF% (37.65).
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Meiotic analysis revealed (study performed for 3 consecutive
years in 3 to 5 randomly selected plants every year; data
pooled over the plants) 2n = 22 chromosomes (1st year – 0.11
IV + 10.29 II + 0.98 I, 236 cells scored; 2nd year - 0.16 IV +
10.78 II + 0.98 I, 182 PMCs analyzed; 3rd year -0.14 IV +
10.63 II + 0.96 I, 164 meiocytes studied) always at
metaphase I (Fig. 2.A-D) and anaphase I (all cells were
cytologically balanced – 11/11 separation of chromosomes).
This result is in conformity to the chromosome number
observed in root tip mitosis, and therefore chromosome
number in the species is 2n = 22 as suggested earlier (n = 11,
x = 6) by Bhattacharya and Datta11.
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Table 1. Karyomorphological details in U. picta
No. of Chromosomes Length (µm)
F%
2
2.625
40.27
2
2.08
37.84
4
1.19 – 1.145
47.06 – 48.47
2
1.105
23.08
2
0.935
32.62
8
0.65 – 0.81
45.21 – 48.05
2
0.59
15.25
Cetromeric nature
Metacentric
Sub-metacentric
Metacentric
Acrocentric
Sub-metacentric
Metacentric
Acrocentric
Fig 1: Metaphase chromosomes of U. picta (2n = 22). A- Karyomorphology (secondary constrictions marked: →). B- Idiogram. Scale bar = 2.0 μm.
Page 163
Fig 2: Meiotic metaphase I. A-C- 11 II; D- 10 II + 2 I (univalents marked). Scale bar = 10.0 μm
Source of support: The work is financially supported by University of Kalyani, Kalyani, West Bengal, Conflict of interest: None Declared
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karyomorphology and chromosome number confirmation in uraria

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