Comparison of some drought tolerance indices in Iranian and foreign safflower (Carthamus tinctorius L.) cultivars

In order to evaluate the drought tolerance of safflower cultivars using some drought tolerance indices, an experiment was carried out as split plot in complete randomize block design with three replications in the research field of Payame Noor University of Khash, during the growing season of 2015-2016. Experimental treatments were consisted of four drought stress levels included cutting-off irrigation at stages of flowering, beginning capsule, ripening stage and no cutting-off irrigation as main factor, and five safflower cultivars included domestic cultivars of Golmehr, Padideh and Faraman; and foreign cultivars of Yut and Nebraska 10 as sub factor. The results showed that the highest seed yield was obtained from treatment of no cutting-off irrigation and Yut cultivar, and the lowest seed yield was related to irrigation cut-off treatment in the flowering stage and Padideh cultivar. Correlation coefficients between drought tolerance indices and seed yield under the conditions of all three stresses showed that MP, GMP, STI, RDI and YI indices had a positive and significant correlation in all three stress conditions with seed yield under control and stress conditions. Therefore, they can be used for better selecting of safflower tolerant cultivars. In addition, the correlation between MP, GMP, STI, RDI and YI indices in all three stress conditions were positive and significant, which due to their correlation with seed yield in all three conditions increases the desirability of simultaneous use of these indices in the selection of cultivars. In general, for safflower cultivars, indices of MP, GMP and STI were the most appropriate indices to evaluate drought stress tolerance in different treatments studied. Based on these indices, as well as biplot diagram and cluster analysis, Yut cultivar was identified as the most tolerant and Padideh cultivar was identified as the most sensitive in all three drought stress conditions.