Drought stress is one of the most important factors limiting the survival and growth of plants in many regions of the world such as Iran. In this research 33 tetraploid wheat genotypes ( Trticum turgidum .) and three genotypes of bread wheat (as control) were used in a randomized complete block design with two replications under two moisture regimes. The experiment was carried out at research farm of Isfahan University of Technology located in Najafabad (Lavark) during 2017-2018 growing season. Results of analysis of variance showed that among all genotypes except for biological yield, carotenoids concentration, electrolyte leakage of leaf, leaf area and specific leaf weight at non-drought stress conditions all other studied traits were significantly different. Under drought stress condition, except for proline concentration, chlorophyll-a, chlorophyll b, carotenoid, total chlorophyll concentration and electrolyte leakage of leaf all other traits were significantly different among the genotypes. This indicated the genetic diversity of the studied genotypes and their different responses to moisture environments. Mean compariso for the studied traits showed that drought stress negatively affected majority of the measured traits except, the number of spikelets per spike, day to flowering, day to heading, leaf length, leaf width, leaf area, proline concentration, carotenoids, electrolyte leakage and specific flag leaf area . In order to study the effect of drought stress on measured traits, percentage reduction of each trait mean value was calculated. Under drought stress condition mean values for peduncle extrusion length, specific leaf weight and grain yield were reduced at 34.65%, 26.19% and 22.06% respectively. Two genotypes No. 2 ( durum wheat Dena cultivar) and No. 5 ( durum wheat Yavarus cultivar) at both water stress and non-stress conditions, had the highest grain yield. Correlation between drought resistance indices and yield at water stress and non-stress conditions indicated that STI, MP and GMP indices were suitable for selection of high yield genotypes in both water stress and non-stress conditions. Genotypes No. 2, 5, 1, 4 and 6 from durum wheat, were recognized as high yield genotypes under both water stress and non- stress conditions. Key Words Tetraploid wheat, Drought stress, Genetic variation, Drought tolerance index.
