Estimation of Combining Ability and Heterosis for Wheat Yield and Its Components under Water Stress Conditions

DROUGHT is a worldwide problem which controls the crop productivity. Six Egyptian bread wheat varieties were crossed in a 6x6 half diallel in 2018/19 season. Parents and their fifteen F1 crosses were evaluated under normal irrigation (N), mid water stress (MS) and severe water stress (SS) during 2019/20 in three field experiments. Results showed that the analysis of variance were significant for all the studied traits. The highest mean values were recorded under all irrigation treatments as well as the combined analysis with the crosses P1x P2, P1 x P3, P1 x P5, P2 x P3, P3 x P5 and P5 x P6 for grain yield per plant. Mean squares for both general (GCA) and specific (SCA) combining ability estimates were highly significant for all studied traits. GCA/SCA ratio was greater than unity for most traits. The parental P1 exhibited positive and significant GCA effects for number of kernels per spike, grain yield per spike and grain yield per plant. The highest desirable SCA effects were obtained with the crosses P3 x P5 and P4 x P5 for grain yield per plant under stresses conditions. Positive significant heterosis were detected by the crosses P1 x P3, P2 x P3, P3 x P5, P4 x P5 and P5 x P6 for number of spikes per plant, number of kernels per spike, grain yield per spike, 1000-grain weight and grain yield per plant at N, MS, SS conditions and the combined data.