Genetic Analysis of Seedling Traits under Drought Stress Conditions in Bread Wheat

In the present study, a laboratory experiment was conducted to study the gene action and estimate general (GCA) and specific (SCA) combining ability of seedling traits in a half diallel cross of bread wheat. Eight bread wheat genotypes and their F 1 hybrids were evaluated under drought stress induced by the treatment with Polyethylene Glycol-6000. The studied traits were shoot length (SHL), root length (ROL), number of lateral roots (NOR), fresh weight of seedling (FRW) and dry weight of seedling (DRW). Highly significant (P<0.01) differences were observed among studied genotypes for all seedling traits under drought stress conditions. Highly significant (P<0.01) mean squares due to GCA and SCA effects were observed for all seedling traits, indicating the importance of both additive and non-additive gene actions. Obviously, GCA mean squares were larger in magnitude than that of SCA, indicating the importance role of the additive gene action in the inheritance of the studied traits. Compared to their parents, F 1 hybrids produced longer roots under drought stress conditions, indicating the presence of heterosis. The regression analysis indicated a partial adequacy of an additive-dominance model for ROL, NOR, FRW and DRW, while non adequate model was observed for SHL. Based on GCA effects, the parental genotypes P 1 , P 2 and P 3 were the best general combiners for most studied traits under drought stress conditions. The highest desirable SCA effects were obtained from the crosses P 1 ×P 3 , P 1 ×P 6 , P 1 ×P 8 , P 2 ×P 5 and P 2 ×P 7 for most studied traits, indicating their usefulness as best promising combinations under drought stress conditions.