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.)

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

GENETICS OF RESISTANCE TO ASPERGILLUS FLAVUS Link ex Fries IN GROUNDNUT (Arachishypogaea L.)

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