The effect of melatonin levels on biochemical properties and the expression of genes related to antioxidant enzymes activity in Triticum aestivum L. under drought stress conditions

To study the effect of different levels of melatonin on the biochemical properties and the amount of expression of genes related to the activity of antioxidant enzymes in bread wheat, a split plot experiment was conducted based on a randomized complete Triticum aestivum block design. Irrigation levels (normal (FC = 80%)), mild stress (FC = 60%), and severe stress (FC = 40%)) were allocated to the main plots and melatonin foliar spray (zero, 50, 100, 150, and 200 μM) were assigned to subplots. The results showed that the flavonoid content and ascorbate peroxidase enzyme activity increased with the intensification of dehydration stress. The level of 100 µM melatonin had the highest flavonoid content, ascorbate peroxidase enzyme activity. The mean comparison interaction treatments showed that the highest content of proline, phenol, superoxide dismutase and catalase was assigned to the 100 µM melatonin foliar spray under conditions of extreme stress of dehydration. Also, the lowest amount of malondialdehyde was observed for the 50 μM melatonin foliar treatment under normal irrigation conditions. The highest content of chlorophyll a, chlorophyll b, carotenoid and grain yield were recorded in the treatment of foliar spray of 100 μM melatonin and normal irrigation conditions. In this investigation, the maximum expression of superoxide dismutase, ascorbate peroxidase, polyphenol oxidase and catalase genes were determined in the foliar spray of 100 and 150 μM melatonin levels under conditions of extreme stress. . The foliar spray of melatonin, especially at the level of 100 μM, could moderate the effect dehydration stress on grain yield by improving biochemical and antioxidant properties.