Evaluation of Autumn Sown Genotypes of Safflower (Carthamus tinctorius) for Tolerance to Drought Stress

Fifteen sufflower genotypes selected from collection of National Plant Gene Bank of Iran were assessed in two separate experiments of normal and stress conditions in randomized complete block design with three replications. Both experiments were irrigated to the time of 50% heading based on 80 millimeter evaporation form class A evaporation pan. From this time on, irrigation was performed based on 180 millimeter evaporation in drought stress experiment. Genotypes 532 from Spain, IL111, 633.1 and 642.2 from Iran and 772.1 from USA had the highest and genotypes 753.2 and 581 the lowest seed yield in both conditions. In principal component analysis on the basis of drought resistance indices, the first two components comprised 96.9% of the total variation in data. Based on the coefficients of indices, the first principal component indicated stress tolerance and the second principal component expresses high yield potential in favorable condition. DRI index was calculated in order to differentiate the variation of seed yield in stress condition from potential seed yield and time of maturity. Coefficient of determination for regression of yield in stress condition on yield in non-stress condition and days to flowering (0.61) indicated that only a part of yield of genotypes in stress condition is affected by potential yield and time of maturity. Cluster analysis located the genotypes within three groups of tolerant, intermediate and susceptible .