The effects of drought stress on grain and oil yield of two cultivars of sunflower

An experiment was conducted to examine the effects of drought stress on two cultivars of sunflower as split plot randomized complete block design at Agricultural Research Center of Khorramabad during 2013 with three replications. Treatments were irrigation at depletion of 25, 50, 75 and 100 available soil water comprising main-plots and two cultivars of sunflower (Record and Alster) as subplots. Drought affected head diameter, grain number per head, 1000 grain weight, core percentage of grain, grain and oil yield and harvest index. Grain yield of Record and Alster at no stress condition were 3359.10 and 3869.35  Kg/ha, respectively and oil yield was 1685.88 and 1818.10 Kg/ha, respectively. Grain yield of Record and Alster at the strongest drought decreased by 45.31 and 62.35%, respectively and oil yield decreased by 49.50 and 60.88 %, respectively. In addition to head diameter, 1000 grain weight and grain number per head significantly decreased at stress condition, led to grain yield decreasing. This results suggested that Alster at stress free condition and Record at stress condition has greater grain yield and drought resistance.