Exogenously applied methyl jasmonate increased the resistance of postharvest pear fruit to blue mold

Methyl jasmonate (MeJA) is a plant-signalling molecule that plays significant roles in stress reactions and defence responses. The goal of this study was to characterize the effects of exogenous MeJA application on the resistance of postharvest pear fruit to blue mould rot caused by Penicillium expansum and investigate the mechanism underlying the observed effects of MeJA application. MeJA treatment effectively reduced the lesion diameter of blue mould rot in pear fruit. Furthermore, MeJA significantly enhanced the activities of antioxidant and defence-related enzymes, such as polyphenol oxidase (PPO), superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), β-1,3 glucanase (GLU) and chitinase (CHI); total phenol content also increased, and membrane lipid peroxidation decreased. MeJA treatment promoted the expression of PpPPO, Cu-ZnSOD, PpPOD, PpCAT, PpCHI and PpGLU. Overall, this experiment suggested that MeJA-induced pear fruit resistance against blue mould rot may be related to the enhanced activities of defence enzymes and gene expression.