Effect of agronomic traits and drought resistance indices on determination of susceptible and tolerant sunflower lines

In order to determine the susceptible and tolerant lines of sunflower to drought stress, a completely randomized block design with three replications was conducted at Karaj seed Oil Research Institute. In this study, 12 different sunflower lines have been identified for the characteristics related to drought tolerance and were selected two susceptible and tolerant lines. Initially, sunflower lines were cultivated in two separate experiments under normal irrigation and drought stress conditions. Drought stress was carried out through stop irrigation in step 2 to 8 leaves formation. The studied traits included agronomic characteristics and drought stress indices of sunflower, such as Plant height, Stem diameter, Head diameter, Seed yield, Leaf Area Index, Relative Water Content, SSI and STI. The studied traits were significantly different in water stress, except stem diameter. After analyzing the tested factors and analyzing the data, the results were obtained by analyzing the percentage of variation of studied traits, calculating stress indices (drought tolerance indices, drought sensitivity) and dendrogram drawing from Cluster analysis of cultivars was identified. According to the results, in terms of water deficit stress, RGK26 and RGK41 produced the highest and the lowest seed yield per plant. Comparison of traits can identify BGK221 as susceptible line and RGK46 as tolerant line among 12 studied lines. Also, correlation between traits showed that drought tolerance index (STI) was positively correlated with almost all traits. In addition, grain yield was positively correlated with all traits except plant height.