Induced Resistance in Yali Pear (Pyrus bretschneideri Rehd.) Fruit against Infection by Penicillium expansum by Postharvest Infiltration of Acibenzolar-S-methyl

The objective of the present study was to evaluate how disease resistance in Yali pear fruit (Pyrus bretschneideri Rehd.) was affected by the infiltration of acibenzolar-S-methyl (ASM) after harvest. The disease incidence and lesion area in/on the fruit inoculated with Penicillium expansum significantly (P < 0.05) decreased by the infiltration with 0.5 mm ASM, and the duration of protection conferred by ASM lasted over 15 days. ASM did not directly inhibit the mycelial growth of P. expansum in vitro. However, ASM treatment significantly enhanced activities of the main defence enzymes including peroxidase, phenylalanine ammonia-lyase and chitinase, and activities of antioxidant enzymes including superoxide dismutase and catalase in the fruit during the infection. Two kinds of second metabolites, total phenolic compounds and flavonoids, and two productions of lipid peroxidation, H2O2 and malondialdehyde, were also involved in the resistance and significantly accumulated in ASMtreated fruit in the infection. The inhibitory effect of ASM on the disease may be related to its ability to enhance defence responses in the fruit. The application of ASM in inducing resistance in fruit possesses promising in control of postharvest diseases alternative to fungicides