Effect of End-of-Season Drought Stress on Grain Yield and Some Morphological Traits in Wheat Genotypes Hexaploid Tolerant and Sensitive to Stress

In order to determine the relationship between stress tolerance and some morphological traits such as day to flowering, day to ripening and plant length in wheat genotypes, an experiment with 180 genotypes in two conditions of terminal water stress (cessation of irrigation from pollination stage onwards) and no stress. It was done in the form of a systematic plan in Khoy Agricultural Research Station. Using two-stage clustering method and based on the values of optimal yield and stress, genotypes with optimal yield capacity and tolerant to stress and genotypes with optimal yield capacity but drought sensitive were identified. In non-stress conditions, the correlation between day to flowering and day to maturity was positive and significant in both groups of genotypes. In terms of stress, intensity and direction of trait correlations in each group were sometimes different from the other group, so that despite the positive and significant correlation between 1000-seed weight and number of days to maturity in tolerant genotypes, this relationship was negative and significant in susceptible genotypes. Also, while the relationship between 1000-seed weight and plant height in tolerant genotypes was positive and significant, this relationship was negative and significant among susceptible genotypes. Under stress conditions and based on path analysis, 1000-seed weight had the most direct positive effect on yield of tolerant genotypes and in susceptible genotypes, the trait of day to maturity had the most direct negative effect on grain yield.