Selection of salinity tolerant lines of sunflower using some physiological characteristics

Abiotic stress such as drought and salinity stresses calculated as important problem in arid and semi-arid regions which having negative impacts on the growth and development of plants. In addition to toxicity effect of salinity stress, it causes drought stress. In this research, for selection of salinity tolerant lines of sunflower using physiological indices, a sunflower germplasm including 100 inbred lines were inspected under both normal and salinity (6 ds/m2) state. Experiment was done in pots which arrayed considering factorial experiment based on complete randomized design with three replications in outdoor conditions. The results showed the significant effect of salinity on seed yield, relative water content, Na+, K+ and K+/Na+ ratio. The effect of genotype was significant on net photosynthesis and chlorophyll content in addition to above mentioned traits. Mean value of studied characters except of sodium concentration were reduced under salt stress compared to normal. In this research, most reduction was observed in K+/Na+ ratio (47.49%), K+ (23.08%) and grain yield (13.84%) and the lowest reduction was observed in chlorophyll content (1.34%) and leaf relative water content (2.67%). Regarding response of the studied lines against salinity stress, inspected germplasm was separated into three groups. Cluster mean comparisons using Tukey test in salinity stress conditions revealed that the highest and lowest mean of traits were observed in clusters II and III, respectively. Recombinant inbred lines including C61, C34, C134a and C153 showed the highest values for most of studied traits specially for K+ content and K+/Na+ ratio. Potassium and potassium/sodium ratio in plant are one of the important criteria for determining salt tolerance; therefore, these lines are potentially introduced as salt tolerant lines.