evaluation of drought tolerance in advanced grain sorghum lines

in order to study of drought tolerance in advanced grain sorghum lines, an experiment was conducted in a split-plot on randomized complete block design with three replications in experimental field of seed and plant improvement institute, karaj, iran during 2009-2010. irrigation regimes were assigned to main plots at three levels including normal irrigation (i1=60mm), moderate stress (i2=120mm) and sever stress (i3=180mm). seven lines including kgs15, kgs19, kgs23, kgs25, kgs27, kgs32 & kgs36 were considered as sub-plots. results on stress susceptibility index (ssi) and tolerance index (tol) showed that lines kgs15 and kgs19 were more tolerant than other lines. stress tolerance index (sti), mean productivity (mp) and geometric mean productivity (gmp) showed that line kgs32 with grain yield 11240 kg/ha under non–stress condition and 6368 kg/ha under stress condition along with line kgs36 determinated as genotypes with highest yield under both optimum irrigation and drought conditions. presense of high and positive correlation between sti, mp and gmp grain yield indicated that all of these indices could be used for selection of drought tolerant genotypes. it is concluded that lines kgs32 and kgs36 are suitable genotypes for cultivation under drought stress conditions.