COMBINING ABILITY AND HETEROSIS FOR GRAIN YIELD AND ITS COMPONENTS IN SOME MAIZE INBRED LINES UNDER DROUGHT STRESS

Abstract

The present study was conducted to evaluate eight white inbred lines of maize and their F1 crosses under normal and drought stress conditions to estimate combining ability and heterosis for grain yield and associated traits. The evaluation was extended to include two transcription factor genes known to be associated with abiotic stresses in plants, namely are DREB2 and CBF4. The results showed significant mean squares (MS) of irrigation treatment were showed for the studied traits. The MS of parents, crosses, and genotypes were determined to be highly significant under both and across irrigation levels, with the exception of the anthesis-silking interval and stay green under normal irrigation, number of ears plant-1 and ear diameter under both irrigation levels for parents and genotypes, and anthesis-silking interval, number of ears plant-1 and ear diameter under both irrigation regimes for crosses. Grain yield and most other traits showed significant differences (MS) associated with both General combining ability (GCA) and specific combining ability (SCA) under both irrigation regimes, demonstrating the importance of both additive and non-additive genetic effects in the expression of performance traits. The drought sensitivity index indicated that the best parents were (P-53), (P-137) and (P-86), and the best crosses were (P-86×P-96), (P-53×P-96), (P-96×P-137) and (P-53×P-137) which gave the highest yield under both environments. The parental line (P-86) had positive and highly significant GCA effects. The crosses (P-17×P-96), (P-8×P-96), (P-8×P-171), (P-24×P-86), (P-86×P-96), (P-86×P-171), and (P-96×P-171), gave the highest specific combinations under both irrigation regimes for grain yield and some of the associated traits. The highest level of heterosis (heterobeltiosis) for grain yield was obtained in