utilization ability of drought resistance indices in sunflower (heliantus annus l.) hybrids

in order to evaluate the utilization ability of drought resistance indices such as: yield index (yi), yield stability index (ysi), stress susceptibility index (ssi), tolerance (tol), mean productivity (mp), geometric mean productivity (gmp) and stress tolerance index (sti) in sunflower hybrids, three separate experiments were conducted as randomized complete block design at the research field of seed and plant improvement institute in iran-karaj, in 2006. the first experiment was conducted at optimum conditions where plants were irrigated after 60 mm evaporation from evaporation pan, class a, whereas the second and third experiments were irrigated after 120 (mild drought stress) and 180 (sever drought stress) mm evaporation, respectively. the results showed that under mild and sever drought stresses only sti by having positive and significant correlation with seed yield under non-stress and stress conditions, was more effective in identifying the high yielding hybrids. the evaluation of hybrids using drought resistance indices indicated that allstar hybrid had maximum leaf area index (lai) and seed yield under mild and sever drought stress as 1671 and 701 kg.ha-1, respectively, and was superior to others.