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Abstract
The inheritance of resistance to the African stem borer, Busseola fusca, in maize was investigated by means of line x tester analyses in the F1 to F4 generations of crosses between 18 susceptible inbred lines and two resistant testers of common genetic background. Based on artificial infestation of plants followed by evaluation of leaf feeding damage, additive gene action was found to be significant for resistance, whereas dominance was nonsignificant in all cross combinations, using phenotypic assessment of gene expression in various generations. However, estimates of genetic components showed both additive and dominant gene action to be important. Significant additive x additive and dominance x dominance gene interactions were found, indicating non-allelic interaction and that resistance is controlled by several genes at different loci. Using a rating scale to test for absence of epistasis indicated one locus non-allelic interaction to be negligible, but did not exclude non-allelic interaction for two or more loci. Heritability in the broad sense was high, while the estimated narrow sense heritability was low, indicating non-additivity of gene effects. Estimates of combining ability showed greater SCA than GCA in most crosses, indicating that the inheritance depended both on the source of resistance and the susceptible inbred parent used in the particular combination. This suggests that each susceptible inbred line possesses one or more of the possible loci from the polygenic pool of resistant genes. Results confirmed that selection for resistance should not be initiated in the F2 generation but from the F3 and onwards, when the segregating variability should be reduced.