evaluation of drought tolerance in cultivars and advanced grain sorghum lines under low irrigation stress conditions

in order to evaluate drought tolerance of cultivars and advanced grain sorghum lines, an experiment was conducted as split-plot on randomized complete blocks design with three replications at experimental field of seed and plant improvement institute, karaj in 2009. three levels of irrigation regimes including normal irrigation (ir0=60 mm), moderate stress (ir2=120 mm) and sever stress (ir3=180 mm evaporation from the surface evaporation pan) were the main plot and the subplots were ten cultivars and advanced lines including (kimiya, payam, sepeede, kgs27, kgs32, kgs23, kgs19, kgs15, kgs36, kgs25). results using stress susceptibility index (ssi) and tolerance index (tol) revealed that payam and sepeede cultivars and kgs19 and kgs15 lines are more tolerant than others. stress tolerance index (sti) and geometric mean productivity (gmp), that their higher values indicate the tolerance of cultivars under stress, revealed kimiya cultivar with grain yield 12026.7 kg ha-1 in non-stress conditions and grain yield 7663.3 kg.ha-1 in stress conditions and kgs32 line with grain yield 12973.9 kg.ha-1 in non-stress conditions and grain yield 8830.6 kgha-1 in stress conditions, as genotypes with highest yield in both optimum irrigation and drought conditions.