Genetic Analysis of Response to Water Deficit Stress in Wheat Yield Traits with Generation Means and Variance Analysis

     Drought stress is the most important environmental stress that affects many morphological, physiological and, especially, yield traits of arable crops. In this research, a cross between the cultivar Gaspard (dehydrated susceptible parent) and DN11 line (drought resistant parent) was performed. F1, F2, F3, BC1 and BC2 generations along with parents, were planted and compared in a randomized complete block design with three replications in normal and water deficit conditions for two years. Then, using generation means analysis and generation variance analysis; genetic parameters were investigated in normal and water deficit conditions. Weighted analysis of variance showed that water deficit stress had a significant effect on the reduction of 100 grains weight, volumetric weight and seed yield per plant. The results of mean generation analysis for 100 grains weight and volumetric weight were the same and the same regression models were obtained for two environments. In addition to additive and dominant effects, epistatic effects also played a role in the inheritance of all studied traits. Additive and dominant effects along with additive×dominant and dominant×dominant interactions effects had played a role in the inheritance of single plant yield, moreover, in biological yield, dominant and dominant×dominant interaction effects had played a role, too. Generations variance analysis showed that the gene action for plant height, 100 grains weight (both conditions), spike length, spikelet number per spike and number of seeds per spike were additive. For the number of spikes and grain yield per plant were dominant and for the volumetric weight (both conditions), overdominance was observed. The results of two generations mean and variance analysis in traits such as biological yield were not the same, which can be attributed to the degree of genetic dispersion and bi-directional dominance. In harvest index and grain yield, due to high environmental variability, narrow sense and broad sense heritability was low.