Arginine induces the resistance of postharvest jujube fruit against Alternaria rot

Abstract In order to explore the effects of arginine (Arg) treatment on postharvest rot of jujube caused by Alternaria alternata (A. alternata), winter jujube was treated with different concentrations of Arg (0, 20, 200, and 1000 μmol/L). Results showed that Arg treatment substantially inhibited the expansion of lesion diameter, and jujubes treated with 200 μmol/L Arg had the smallest lesion diameter. In vitro experiments demonstrated that Arg could not inhibit spore germination and mycelial growth of A. alternata. Further experimental results showed that Arg treatment reduced the production rate of O2–. and H2O2 content and improved the activities of superoxide dismutase, catalase, peroxidase, and ascorbate peroxidase in comparison with the control; Arg treatment enhanced the activities of chitinase and β-1,3-glucanase. Furthermore, Arg treatment significantly increased the activity of phenylalamine ammonia lyase and the contents of flavonoids, phenolics, and lignin. Results indicated that, although Arg could not directly inhibit the growth of pathogenic fungi as a fungicide, it can induce resistance to Alternaria rot by maintaining the balance of reactive oxygen species, increasing the activities of pathogenesis-related protein, and promoting the phenylpropane metabolism in jujube fruit tissue. Therefore, Arg treatment can be a novel measure for inducing the resistance of jujube to postharvest Alternaria rot.