Effect of salicylic acid on photosynthetic pigments content, antioxidant enzyme activity and yield components of three sesame genotypes under different irrigation regimes

Drought stress is one of the most important abiotic stresses that has harmful effects on productivity of crops, including oilseed crops. Salicylic acid is one of the plant growth regulators that plays a key role in plant resistance against environmental stresses, including drought. Therefore, a factorial randomized complete block pot experiment with three replications was designed to assess the effect of salicylic acid (two levels of 0 and 0.6 mM) on three sesame genotypes (Yekta, Shiraz and Nazetakshakheh) in the presence of three levels of irrigation (irrigation after 60, 70 and 80% of available soil water depletion) in the greenhouses of Isfahan University of Technology, Isfahan, Iran in 2016. Results showed that chlorophyll a, b and a+b concentrations, number of capsules per plant, number of seeds per capsule and seed weight per plant were decreased in stressed plants, while carotenoids concentration and activity of antioxidants enzymes including catalase, ascorbate peroxidase, and peroxidase were increased under stress conditions. Application of 0.6 mM salicylic acid improved the measured traits under both control and stress conditions. Salicylic acid improved the tolerance of sesame against drought. With increasing drought levels (irrigation after 70 and 80% of available soil water depletion), Yekta and Shiraz genotypes had less decrease in measured traits in pot experiment.