Genetic analysis of drought tolerance and earliness in tropical maize (zea mays l.) germplasm

Abstract

Drought is a major production constraint limiting maize production in sub-Saharan Africa. Adoption of improved hybrid maize cultivars with resilience to drought stress is necessary for enhanced productivity in the semi-arid areas. The objectives of this study were; (i) identify elite single-cross maize hybrids that are drought tolerant and early maturing for semi-arid Kenya and (ii) to estimate the combining ability effects for drought tolerance and earliness among single-cross maize hybrids in semi-arid Kenya. Two experiments were carried out at the Kenya Agricultural and Livestock Research organization Katumani Research Centre and Kiboko sub-Centre. The first experiment involved evaluation of ninety-one single-cross maize hybrids alongside seven commercial checks for drought tolerance under random and managed drought conditions in two replications. In the second experiment, eleven parents were crossed a half diallel mating design excluding self’s and reciprocals to generate fifty-five crosses. The fifty-five crosses were evaluated alongside two commercial checks in an alpha-lattice design with two replications. Results from the first experiment revealed significant differences (p<0.05) for genotypes, locations and genotype by location interactions for yield and yield related traits studied. Broad sense heritability for grain yield trait of 61.93% was recorded under managed drought and 1.95% under to random drought while anthesis-silking interval recorded 3.02% and 8.2% respectively. Genotypes KAT-DT-EE-02, KAT-DT-EE-04 and KAT-DT-EE-05 recorded the lowest cultivar superiority values of 0.20, 0.23 and 0.26 respectively on the cultivar superiority index hence were consistently well ranked across the test environments. From the second experiment, crosses KAT-DT-EE-07×KAT-DT-EE-14 (6.18t ha-1) and KAT-DT-EE-07×KAT-DT-EE-04 (6.16t ha-1) had superior grain yield while KAT-DT-EE-07×KAT-DT-EE-14 showed significant low values for anthesis silking interval (0.5) hence adapted to drought. Genetic analysis revealed significant (p<0.05) general combining ability and specific combining ability mean squares for most measured traits which underscored the importance of both additive and non-additive genetic variance in their inheritance. Significant interaction of general combining ability with location effects demonstrated the need for multi-location testing of potential cultivars. Cross KAT-DT-E-06×KAT-DT-EE-04 (-0.27*) had significant specific combining ability for a reduction in anthesis silking interval in managed drought conditions. Significant specific combining ability effects for grain yield were recorded in KAT-DT-M-31×KAT-DT-EE-07(1.72*) which demonstrated the potential of obtaining drought tolerant hybrids for possible future deployment to farmers in drought endemic areas.