Document 6558334

OCCURRENCE OF F U S A R I U M HEAD BLIGHT, ASSOCIATED MYCOTOXINS
AND RESISTANCE OF WHEAT GERMPLASM
OLIVER OTIENO OKUMU
(B.Sc. Agriculture, University of Nairobi)
THESIS SUBMITTED IN PARTIAL FULFILLMENT OF T H E REQUIREMENT
FOR T H E DEGREE OF MASTER OF SCIENCE IN CROP PROTECTION
DEPARTMENT OF PLANT SCIENCE AND CROP PROTECTION
F A C U L T Y OF AGRICULTURE
UNIVERSITY OF NAIROBI
2014
DECLARATION
This is my original work and it has not been submitted for award of a degree in any other
University
Oliver Otieno Okumu
Signature:
Date:
This thesis has been submitted for examination with our approval as University supervisors
Prof. James W. Muthomi
Department of Plant Science and Crop Protection
University of Nairobi
Signature: - - - C M .
Date:
S^Stl!^
Dr. Maina Wagacha
School of Biological Sciences
University of Nairobi
7
Signature:
Date
Dr. Charity Mutegi
International Institute of Tropical AgricultHfe (IITA), Nairobi
Date:-J-^3.1MH
Signature:^^^
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ABSTRACT
F u s a r i u m head blight (FHB)
is an important disease of wheat that reduces yield and quality
through contamination with mycotoxins detrimental to human and livestock health. Major
wheat varieties grown in Kenya are susceptible to F H B and there is no known source of
resistance to the disease available. This study was carried out to determine the occurrence of
F u s a r i u m head blight, associated mycotoxins and the level of susceptibility of wheat
germplasm to FHB and deoxynivalenol (DON)
contamination.
A survey was carried out during the 2013 cropping season in four agro-ecological'zones
(AEZ)
in Nakuru County to determine wheat production practices and incidence and severity
of FHB in each farm. F u s a r i u m species and mycotoxins DON and T2-toxin were determined
in wheat heads and kernels. Nine wheat varieties and four C I M M Y T lines were evaluated for
susceptibility to F H B in field experiments at diverse agroecolgical zones in Nakuru and
Narok Counties and in the greenhouse. After inoculation with F . g r a m i n e a r u m susceptibility
was determined based on FHB
severity, reduction in grain yield, kernel infectionand DON
contamination in kernels.
Majority (47.4%) of the farmers used certified wheat seeds and variety Njoro BW2
was the
most widely grown. Most (63.4%) of the farmers used wheat straw to make hay for livestock
feed, applied soil amendments (100%), practiced crop rotation (81.3%) while only 6.5% of
the farmers practiced mixed cropping. Rust was the most important disease in all the farms
surveyed. Head blight was prevalent (100%) in all the agro-ecological zones and mean
incidence and severity ranged from 10.6 to 12.5% and 12.9 to 2 0 . 9 % , respectively with the
highest incidence and severity in agro-ecological zone LH3.
F u s a r i u m spp were F . g r a m i n e a r u m , F . avenaceum
contaminated with mycotoxins DON
The most frequently isolated
and F . p o a e . Most wheat samples were
and T-2 toxin upto 182ng/g and 37ng.g respectively.
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Ninety eight percent of the samples contained T-2 toxin above the limit of detection of
3.5ng/g while 46% of the samples contained DON above the limit of detection of 18.5ng/g.
Wheat varieties and lines varied in susceptibility to F . g r a m i n e a r u m with variety Kwale
showing least susceptibility while line 10155 was the most susceptible. Variety sunbird had
the highest mean F H B severity and A U D P C in Nakuru while line 10155 had the highest
mean severity and A U D P C in both the greenhouse and Narok trials. In Nakuru variety Kenya
Hawk had the highest yield of 878g while Kenya wren had the lowest (167g). In Narok, Kibis
had the highest grain yield of 128g while line 957 gave the lowest yield of 59g. A l l the wheat
varieties and lines accumulated DON
with variety Chiriku having the least concentration of
457ng/g while line 10155 had the highest concentration of 748ng/g. Deoxynivalenol
accumulation in grain samples from the greenhouse was lower compared to the samples from
the field trials.
Most grain samples were contaminated with DON
and T-2 toxin. Mycotoxin levels varied
depending on the A E Z and the pre-dominant F u s a r i u m species isolated from a region.
Variety selection and crop rotation influenced the occurrence of FHB
in the different agro-
ecological zones. Although host resistance is the best option in the management of FHB, the
varieties currently available do not confer resistance to both the FHB and DON accumulation.
Therefore, more research on developing resistant varieties should be done in the country.
Key words: Deoxynivalenol, F u s a r i u m , head blight, mycotoxins, T-2 toxin.
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