Physiological Responses of Sesame Cultivars to the Application of Nano Magnesium and Chitosan Biopolymer under Different Irrigation Regimes

To investigate the physiological responses of sesame cultivars to the application of nano magnesium and chitosan biopolymer under different irrigation regimes, a split factorial based on randomized complete block design has been conducted with three replicates between 2017 and 2018. The irrigation cut-off, based on BBCH scale, has served as the main factor (normal irrigation, irrigation up to 50% flowering, and seed ripening), with the sub factors including Oltan and Dashtestan-2 sesame cultivars, and nano magnesium (application and non-application) and chitosan (control, 4.8, and 6.4 g.L-1). The highest mean grain yield belongs to the application of 6.4 g.L-1 chitosan under normal irrigation with an average of 1235.1 kg.ha-1. Also, the highest total chlorophyll content is observed in Dashtestan-2 genotype under normal irrigation with a mean of 24.7 mg.g-1 FW and the lowest mean have been obtained in both genotypes under irrigation up to 65 BBCH with a mean of 17.21 and 17.46 mg.g-1 FW, respectively. Application of nano fertilizer in Oltan genotype under irrigation up to 65 BBCH increases the catalase activity by 41.11%, compared to the control treatment. The highest activity of ascorbate peroxidase has been achieved when not applying chitosan under irrigation conditions up to 65 BBCH. It has risen by 55.06%, compared to the control treatment. In general, the results show that irrigation up to 65 BBCH reduces grain yield, in turn alleviated by the negative effects of stress on magnesium and chitosan nanoparticles (9.93% and 27.46%, respectively). Based on the regression analysis results, four traits, namely chlorophyll b, total chlorophyll, proline, and catalase, enter the model that explains 42.11% of the total grain yield variations. Results of simple correlation between traits and regression analysis indicate the indirect effects of physiological traits on grain yield and among the studied parameters, photosynthetic pigments has been of high account in stress conditions.