MeJA and MeSA alleviate black rot in winter jujube caused by Alternaria tenuissima by regulating membrane lipid and reactive oxygen metabolism

Black rot is a serious disease caused by Alternaria tenuissima (A. tenuissima) that affects winter jujubes. This study explored the effects of MeJA and MeSA on disease resistance in winter jujubes by regulating membrane lipid and reactive oxygen metabolism in response to A. tenuissima infection. MeJA and MeSA significantly reduced the disease severity in winter jujube, enhanced the activity and gene expression of antioxidant-related enzymes, inhibited the activity and gene expression of membrane lipid oxidation-related enzymes, delayed the decomposition of ascorbic acid, glutathione, phosphatidylcholine, and phosphatidylinositol, inhibited the accumulation of hydrogen peroxide, phosphatidic acid, and malondialdehyde, the production rate of superoxide anion and a rise in relative electrical conductivity, and maintained winter jujube cell membrane unsaturation (U/S). Compared with the sterile water treatment, the regulation of membrane lipid metabolism and ROS metabolism in winter jujube fruits by MeJA and MeSA could be a contributing factor to their enhanced resistance against A. tenuissima. The membrane lipid oxidation degree in the MeJA group was lower, indicating that MeJA had better application prospects in disease resistance and storing and preserving winter jujube than MeSA.