Foliar-Applied Melatonin Alters Grain Yield and the Fatty Acid Profile of Sesame (Sesamum indicum L.) Under Drought Stress

Sesame is a valuable oil plant due to its high-quality and stable oil. However, drought is a crucial factor that reduces agricultural productivity worldwide, having a destructive effect on different stages of sesame growth, causing a decrease in yield and yield components in sesame genotypes. Therefore, a study was conducted to investigate the effects of water stress and melatonin foliar spraying on sesame oil’s antioxidant properties and fatty acid compounds (Mina cultivar) during the years 2022–23. The study was done in a split plot based on a randomized complete block design with three replications. Drought stress in the form of irrigation interruption at different stages of plant development was implemented, with four control levels of full irrigation, interruption of irrigation at the stage of vegetative growth, reproductive growth, and vegetative + reproductive growth in the main plots. Melatonin foliar was done at three levels of 0, 0.5, and 1 mM in the sub-plots. During the physiological ripening stage, the seeds were harvested, and their oil was extracted. A gas chromatography device, equipped with a mass spectrometer, was used to determine the fatty acid profile of the oil. The results showed that drought stress significantly (P < 0.01) affected the amount of oleic acid, total unsaturated fatty acids, total fatty acids, and other components. The most abundant unsaturated fatty acids were oleic and linoleic acids. Drought stress caused a significant decrease in grain yield and oil percentage. In both conditions of irrigation interruption (vegetative and flowering stages), the total percentage of saturated and unsaturated fatty acids showed a significant decrease.