BREEDING BREAD WHEAT FOR TOLERANCE TO DROUGHT STRESS

A half diallel cross among eight parents of wheat (Triticum aestivum L.) was evaluated under recommended irrigation and drought stress in RCBD with three replications. Mean squares for genotypes, parents, crosses and parent vs. crosses were significant for the most measurements in both irrigation treatments as well as the combined analysis. The highest mean values were detected under stress condition and combined analysis by parents P4, P6, P8, P7, P1 and P8 for stomatal conductance (SC), net photosynthesis rate (Pn), protein percentage, ash percentage, carbohydrate percentage and grain yield/plant, respectively. Meanwhile, the highest mean values were recorded under stress condition and combined analysis with crosses P1 x P6, P5 x P8, P3 x P4, P3 x P4 and P2 x P5 for stomatal conductance (SC), net photosynthesis rate (Pn), protein percentage, ash percentage, carbohydrate percentage and grain yield/plant, respectively. Superiority percentage relative to check variety Sahel 1 for grain yield/plant was obtained by crosses; P2 x P5, P2 x P4, P2 x P7, P1 x P3, P3 x P6 and P5 x P7 under normal and stress irrigations and for the combined analysis. The mean squares were significant for the most measurements in both irrigation treatments as well as the combined analysis for general combining ability (GCA) and specific combing ability (SCA). GCA/SCA ratio, which exceeded the unity was obtained for LT, protein percentage, carbohydrate percentage, ash percentage and grain yield/plant in both irrigations treatments and the combined analysis. For chemical measurements (protein, carbohydrate and ash percentages) and grain yield/plant the ratio of SCA x I/SCA was much higher than the ratios of GCA x I/GCA. The parental lines P1, P2 and P3 for SC and P5, P6 and P7 for grain yield/plant, exhibited significant positive i g ˆ effects were recorded by the cross P3 x P4 under stress irrigation for LT, TR, Pn and carbohydrate percentage, P1 x P5 and P4 x Gem.9 in the combined analysis for stomatal conductance; P4 x P5 and P5 x P8 under normal, stress irrigation treatments and the combined analysis for protein percentage. The crosses P3 x P4, P1 x P5, P4 x P5, P4 x P6 and P5 x P8 were prospective in wheat breeding program since they expressed the highest ij S ^