Evaluation of physiological traits associated with yield and stress tolerance in different cultivars of sunflower

To study the relationship between drought tolerances in varieties of sunflower with some of physiological traits, an experiment with nine varieties of sunflower was conducted in randomized complete block design with three repetitions in two full irrigation conditions and moisture stress in the summer of 2012. Physiological traits were measured, during the growth. Physiological characteristics such as leaf water content, efficiency of PS II and chlorophyll content were measured in two stages 10 and 20 days after onset of stress and stability of Cytoplasm membrane were measured during a stage after starting stress. Then the data were analyzed as a composite and after comparison of the average and determine of the most tolerant varieties, correlations were calculated between different traits. Results showed that there was inverse and significant relation between the content of damages to PS II with relative content in condition of the tension. Also there was positive and significant relation between STI with performance, chlorophyll and for damages to PS II and in non stress condition was significant, positive inverse relation between the relative content. Relationship between STI as well as the performance and relative content of leaf water was positive and significant. According to the results, the genotypes of Gabor, Lakumla, Armavirsky, Progress and Azar Gol was introduced as high product and superior in non stress condition. With regard to drought tolerance index (STI) cultivar of Gabor as drought tolerant varieties and Sur cultivar were identified as susceptible to stress.