Combining ability analysis for maydis leaf blight resistance in maize

Maydis leaf blight caused by Bipolaris maydis is one of the economically most important diseases and a major constraint in maize production in India. Inheritance of resistance to maydis leaf blight can be known through the value of heritability. The aim of this study was to determine the combining ability effects for disease severity to Bipolaris maydis, heritability and genetic advance for resistance to maydis leaf blight in maize crosses. The eight parental inbred lines were crossed in Line x Tester mating design to produce sixteen F₁ and were advanced to F₂ populations. Test plants were artificially inoculated with maydis leaf blight fungus. Analyses of variance for reaction of disease showed significant differences among 24 genotypes (16 crosses and 8 parents) for maydis leaf blight. The GCA and SCA effects were significant and indicated both additive and non additive genetic mechanisms contributed significantly in the inheritance of resistance to the maydis leaf blight disease. The estimates of heritability in broad sense and narrow sense varied in most of the crosses. The narrow sense heritability values were lower than those of broad sense heritability indicated that most of genetic variance was due to non-additive effects i.e., dominance or epistasis. The H_bs in sixteen crosses ranged from moderate to very high i.e., from 58.10% to 89.15%. The heritability in narrow sense estimates ranged from low in cross HKI 1332 x HKI 193-2-2 to high in cross HKI 209 x HKI 164D-4-(O). The higher estimates of heritability and genetic advance indicated that selection for maydis leaf blight resistance was likely to be more effective in crosses HKI 209 x HKI 164D-4-(O), HKI 209 x HKI 193-2-2, HKI 1332 x HKI 1128, HKI 325-17AN x HKI 193-2-2 and HKI 488-1RG x HKI 164D-4-(O).