CHANGES IN PHYSIOLOGICAL TRAITS AND FATTY ACID COMPOSITION IN SESAME (SESAMUM INDICUM L.) CULTIVARS UNDER VARIOUS FOLIAR APPLICATION AND DROUGHT STRESS CONDITIONS

Sesame is a source of excellent vegetable oil (35-63%). The present study aimed to evaluate the effect of phosphorus nano-chelate and chitosan application under end-season drought stress conditions based on split plot-factorial in three replications in the research field of Shahed University in Tehran, Iran during 2015-16 on the cultivation of sesame during summer. Main plots included drought stress in three levels including full irrigation as control (non-stress), irrigation cut-off at 50% seed ripening (75 BBCH), and 50% flowering (65 BBCH) as mild and severe stress levels, respectively. Subplots consisted of spraying treatments at four levels including non-spraying (control), phosphorus nano-chelate (2 ppt), chitosan (3 g.L-1), and a combination of phosphorus nano-chelate + chitosan, as well as two cultivars such as sesame Oltan and Naz. Based on the results, the effects of drought stress, foliar application, and cultivar were significant on seed yield, oil and protein contents, peroxidase activity, and palmitic acid content. The highest seed yield was achieved by using phosphorus nano-chelate in Naz cultivar under full-irrigation condition (2114.7 kg.ha(-1)). Severe drought stress caused a decrease in more than 60%, compared to the control treatment. Regarding foliar treatments, the highest percentage of oil was observed in using phosphorus nano-chelate, as well as the integrated use of phosphorus nano-chelate and chitosan, which increased by 12.39 and 14.97%, respectively, compared to the control treatment. Oil content in the seed of Naz cultivar was 7.22% higher than that of Oltan cultivar seed. In addition, the severe drought stress and Naz cultivar had the highest seed protein percentage (23.43 and 22.49%, respectively). The activities of catalase and superoxide dismutase antioxidant enzymes were directly related to an increasing drought stress. Further, Oltan cultivar had the highest activities of SOD and PDX enzymes. The highest saturated fatty acids (palmitic and stearic) content were achieved in the non-foliar application (control treatment) in Oltan cultivar. Regarding the interaction effects of foliar treatment and cultivar, the lowest linoleic percentage was achieved in Oltan cultivar under non-foliar treatment and the highest percentage of the acid was observed in other treatments. In conclusion, the foliar application of phosphorus nano-chelate and chitosan improved the quantitative and qualitative yield of sesame and increased the growth and quality under drought stress condition.