Assessing Aegilops tauschii genotypes to drought stress using tolerance indices

The drought and its effect are the most important and common environmental stress that has limited agricultural production in the world. One of the useful strategies of crop breeding for drought resistance is maintaining and exploiting the diversity of their germplasms. To identify drought tolerant sources, 125 Aegilops tauschii genotypes in an augmented designwith three replications under twocontrol (supplementary irrigation in three stages of jointing, flowering and seed filling) and drought stress (without supplementary irrigation) conditions were cultivated and evaluated based on tolerance indices. Correlation coefficients between yield and tolerance indices showed that the indices ofmean productivity (MP), geometric mean productivity(GMP), stress tolerance index(STI) and tolerance index (TOL) were suitable for identifying high yielding genotypes under both stress and non-stress conditions. Based on these indices, genotypes 50, 55, 58 and 65 were identified as the most tolerant genotypes and genotypes 45, 34, 3 and 9 as the most sensitive genotypes. Cluster analysis based on tolerance indices using between-group average method (UPGMA) classified the studied genotypes into seven different groups. Genotypes number 50, 55, 58, and 65, with the highest values for above mentioned indices, were placed in two groups three and five. Finally, according to the results of different analyzes, genotypes number 50 and 55 were identified as the most tolerant genotypes, which could be considered as suitable genetic sources in wheat breeding programs for drought tolerance.