effect of water deficit stress on yield, water use efficiency and harvest index of sesame (sesamumindicum l.)varieties

drought stress is one of the important environmental factors reducing grain yield of plants in arid and semiarid regions. study the effect of water deficit stress on yield, water use efficiency and harvest index of sesame varieties, this experiment was conducted as a split plot based on a randomized complete block design with three replications, at agriculture and natural resources research center in parsabad, ardebil province, in 2008-2009. in this experiment, irrigation was allocated to the main factor at three levels (50, 75 and 100 percent of plant water requirement) and ten sesame varieties. the cropwat-4 software was applied to calculate the amount and time of irrigation (water requirements of plants) in studied irrigation regimes. results of the analysis of variance showed significant differences between cultivars and irrigation regimes for grain, biological yield, harvest index, water use efficiency for grain and biological yield traits. interaction between irrigation regimes and cultivars were significant on grain water use efficiency and harvest index traits. comparisons of means showed that under water stress condition, the grain and biological yield were decreased and the value of water use efficiency for grain, biological yield and harvest index were increased. in irrigation treatment with amount of 50 percent plant water requirement, the amounts of harvest index, grain water use efficiency for grain and biological yield were greater than other tow treatments. ’karaj 1‘, ’ultan‘ and ’is‘ varieties had the highest value and ’indian 14‘ cultivar had the lowest value of biological yield, water use efficiency used for grain and biological yield. therefore, ’karaj 1‘, ’ultan‘ and ’is‘ varieties due to high yield, water use efficiency for grain and biological yield had ability to growing in water deficit regions.