Response of wheat to post-anthesis water stress, and the nature of gene action as revealed by combining ability analysis

Post-anthesis water stress is a major limitation to wheat grain yield globally. Understanding the nature of gene action of yield related traits under post-anthesis water stress will help to breed stress-resilient genotypes. Four bread wheat genotypes having varying degree of drought tolerance were crossed in a full-diallel fashion and the resultant crosses along with the parental genotypes, were subjected to water stress after the onset of anthesis in order to investigate their comparative performance and nature of gene action. Parental genotypes Babax (B) and Westonia (W) performed better compared with C306 (C) and Dharwar Dry (D) with respect to relative reduction in grain yield and related traits under stressed condition. Direct cross B x D and reciprocal cross W x C were more tolerant to water stress, while cross between C306 and Dharwar Dry, either direct or reciprocal, produced more sensitive genotypes. Combining ability analysis revealed that both additive and non-additive gene action were involved in governing the inheritance of the studied traits, with predominance of non-additive gene action for most of the traits. Among the parents, Babax and Westonia were better combiners for grain yield under stress condition. B x D in stressed condition, and C x W in both stressed and stress-free conditions, were the most suitable specific crosses. Moreover, specificity of parental genotypes as female parents in cross combination was also evident from the significant reciprocal combining ability effects of certain traits. Low to medium narrow sense heritability and high broad sense heritability were observed for most of the studied traits in both well watered and water stress conditions. The results of the study suggested that specific cross combinations with high specific combining ability involving better performing parents with high general combining ability may generate hybrids as well as segregating populations suitable for further breeding programs.