Evaluation of Bread Wheat Genotypes for Terminal Drought Stress Tolerance in South-Warm Regions of Iran

Six bread wheat advanced lines and nine lines selected from Seri/Babax population with Chamran cultivar as the cheek were evaluated in three locations in two cropping seasons (2009-2011). Two separate experiments including optimum irrigation until physiological maturity and terminal drought stress were applied in each location using complete randomized block design with three replications. Drought stress tolerance of the genotypes to were evaluated by 15 indices. Results showed that simple and multiple effects of experimental factors were significantly different under well-watered and terminal drought stress conditions. Grain yields of Chamran cultivar were 6056 kgha-1 and 5109 Kgha-1 and the grand mean of grain yield were 6006 kgha-1 and 4667 kgha-1 under well-watered and terminal drought stress conditions, respectively. The highest grain yield was obtained from line No. 9 with 6376 kgha-1 under optimum condition. None of genotypes yielded more grain than Chamran cultivar under terminal drought stress. Except in a few instances, there were no similar genotypes grouping based on susceptibility and tolerance criteria used in this research. Modified stress tolerance (MSTI) and yield index (YI) efficiently distinguished better the genotypes. According to the results of this study lines No.4, 9 and 12 with 6337, 6376 and 6242 kgha-1 grain yield under optimum condition and with 4730, 4781 and 4785 kgha-1 grain yield under terminal drought stress showed higher drought tolerance than the other genotypes. Considering the stress intensity (SI = 0.22) of this study, it seems that high yielding genotypes selected under optimum condition, will also produce higher grain yield under terminal drought stress condition.