Effects of paclubutrazol on water-less stress tolerance mechanisms of two sesame (Sesamum indicum L.) genotypes

Drought is one of the most important abiotic agents that adversely affect the growth and development of plants. The arid and semi-arid regions where sesame (Sesamum indicum L.), as a relatively drought tolerant plant, is grown are specified by high temperatures. In order to evaluate the effects of paclubutrazul (PBZ) on the drought tolerant of sesame a factorial experiment were conducted based on randomized complete block design with three replications in 2014 at greenhouse of Educational Department of Kordkoy (Golestan province). Treatments included two genotypes of sesame (Yellow- white and Oltan), three levels of watering (20, 50 and 80% FC) and three concentrations of PBZ application (0, 7.5 and 15mg/L). Traits such as chlorophyll a, b and carotenoid contents, superoxide dismutase and peroxidase activity, yield and yield components were measured. Data were analyzed with SAS software. Results showed that genotype, water treatment and PBZ had a significant effect on chlorophyll a, b and carotenoid contents, superoxide dismutase and peroxidase activity of roots and leaves, yield and yield components. High PBZ application where plants exposed to the severe water stress significantly improved chlorophyll b (44%), superoxide dismutase of roots and peroxidase activity of roots and leaves. Yellow-white genotype showed higher chlorophyll a (30.4%), b (40.6%) and carotenoid concentration (29.9%), superoxide dismutase of roots (3times), superoxide dismutase of leaves (1.9 times) and peroxidase activity of roots (3times) in severe water deficit stress. Finally, it can be concluded that Yellow white responded better to drought stress than Oltan genotype with maximum levels of PBZ throughout antioxidant mechanismes.