Screening of selected Soybean genotypes for resistance to the Adzuki bean bruchids (Callosobruchus chinensis L.)
Nakaziba, Shakira Kakaire
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Soybean as a legume is important for nutritional benefits (high protein and oil content), animal feed and soil fertility improvement. Despite its importance, it is constrained by storage pests such as bruchids for example Callosobruchus chinensis. The use of host resistance is one of the approaches for managing the bruchids in storage. Soybean germplasm in Uganda is, however, not fully explored for resistance to the bruchid. Thus there is a necessity for screening for resistance. Therefore, an experiment was conducted at Makerere University Agricultural Research Institute Kabanyolo to screen soybean genotypes for possible sources of resistance to Callosobruchus chinensis. The experiment was laid out in a completely randomized design with three replications. Fifty (50) seeds of each of the 32 genotypes were placed in petri dishes and artificially infested with 20 1-3 days old unsexed bruchids under a no choice test. The variables used to evaluate resistance/susceptibility of the 32 genotypes, included number of eggs laid, adult bruchid emergence (ABE), median development period, growth index, Dobbie susceptibility index (DSI) and percentage weight loss. Data obtained was analyzed using Genstat Statistical Package 14th edition. The analysis of variance showed that the 32 genotypes were not so different from each other as there were no significant differences (P > 0.05) for all the variables except for ABE (P = 0.048). Using means of DSI, the three most resistant genotypes were AVRDC84051-31-1, USA6(B1), and NAM11. Correlation and regression analysis indicated a positive relationship between ABE and percentage weight loss. Genotype AVRDC84051-31-1 was therefore the most resistant while the other 31 genotypes were moderately resistant. Genotype AVRDC84051-31-1 could therefore be used as a source of resistance, for future breeding for resistance to the bruchid.