Methionine enhances disease resistance of jujube fruit against postharvest black spot rot by activating lignin biosynthesis

Abstract

The present research is focused on the effect of methionine on black spot rot caused by Alternaria alternata on jujube fruit and the possible mechanism involved. The results showed that 0.1 g L−1 methionine could induce disease resistance against A. alternata in jujube fruit; however, 0.1 g L−1 methionine did not directly inhibit the growth of A. alternata in vitro. According to the transcriptome analysis, it was observed that the enzymatic activities (PAL, 4CL, COMT, POD, and LAC), the expression of the corresponding genes, and the MYB genes related to lignin synthesis increased by 0.1 g L−1 methionine treatment. Moreover, a higher lignin content was observed in jujube fruit treated with 0.1 g L−1 methionine. These results suggest that 0.1 g L−1 of methionine increased jujube resistance against black spot rot, primarily by activating lignin biosynthesis, rather than directly inhibiting the pathogen. The present research indicates that methionine can potentially be used as a safe and reliable alternative fungicide for the control of postharvest infection in fruit.