GENETICS OF RESISTANCE TO ASPERGILLUS FLAVUS Link ex
Fries IN GROUNDNUT (Arachishypogaea L.)
GENETICS OF RESISTANCE TO ASPERGILLUS FLAVUS Link ex
Fries IN GROUNDNUT (Arachishypogaea L.)
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Date
2012-06
Authors
BALA, DEBORAH
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Abstract
The mode of inheritance to surface seed colonization by Aspergillusflavus Link ex Fries and
aflatoxin contamination in groundnut (Arachishypogaea L.) was studied from four groundnut
varieties. Two varieties were reported to be resistant (J11 and 55-437) and the remaining two
susceptible (Samnut23 and Samnut 22). Each resistant variety was crossed to the two
susceptible varieties in a bi-parental mating design in the screen house of the Institute for
Agricultural Research, Ahmadu Bello University, Samaru Zaria. Six genetic populations (P1,
P2, F1, F2, BCP1 and BCP2) were developed which were evaluated for surface seeds
colonization by inoculation with conidia of Aspergillusflavus in the laboratory. The
inoculated seeds were incubated at 28oCfor 8 days, at the end of which the seeds were rated
for surface seeds colonization. Aflatoxins were extracted from the inoculated seeds by
column chromatography and analysed for aflatoxin content by thin layer chromatography
(TLC). The data collected were subjected to analysis of variance by the general linear model
(GLM) of the statistical analysis systems (SAS). The data was also subjected to scaling tests
to test the adequacy of the additive –dominance model. The A,B,C scaling tests used to test
the adequacy of the additive -dominant model to explain the within population variation were
not significant, indicating that the model was adequate. There was significant variation
among the parental genotypes for the mean surface seed colonization by Aspergillusflavus
and aflatoxin content.The genotypes J11 and 55-437 earlier reported to be resistant to invitro
seed colonization by Aspergillusflavus showed moderate to high surface seed colonization
and different levels of aflatoxin contamination. The means of the parents in relation to their
progenies revealed preponderance of dominance gene effects.The number of effective factors
estimated for surface seed colonization and aflatoxin content ranged from 1 to 2
respectively.Frequency distribution of the F2 and backcross populations and the number of
effective factors segregating for the two parameters studied indicated monogenic inheritance.
Heritabilitywas also estimated for surface seed colonization and aflatoxin content.Broad
sense heritability estimates ranged from 42.92% to 85.30 % and 56.31 % to 84.46 % for
surface seed colonization by Aspergillusflavus and aflatoxin content, respectively. Narrow
sense heritability also ranged from 9.38 % to 33.91 % and 18.85 % to 54.82 % for the two
parameters studied. The moderate to high heritability estimates revealed that the traits are
highly heritable and selection can be practiced to improve them
Description
A thesis submitted to the School of Postgraduate Studies, Ahmadu Bello
University, in partial fulfillment of the requirements for the award of Degree of
Master of Science in Plant Breeding
DEPARTMENT OF PLANT SCIENCE
FACULTY OF AGRICULTURE
AHMADU BELLO UNIVERSITY
ZARIA, NIGERIA
JUNE, 2012
Keywords
GENETICS, RESISTANCE, ASPERGILLUS FLAVUS Link ex Fries, GROUNDNUT, (Arachishypogaea L.)