Enhancing disease resistance in peach fruit with methyl jasmonate

BACKGROUND: Peaches are susceptible to microbial decay during postharvest distribution at ambient temperature. To search for effective alternatives to currently used fungicides for disease control, in this study the effect of methyl jasmonate (MeJA) on disease resistance and fruit decay of peaches after harvest in response to pathogen attack was investigated. RESULTS: Freshly harvested peaches were treated with 1 µmol L^?1 MeJA vapour at 20 °C for 24 h. At 0, 12, 24 and 36 h after this treatment, both treated and untreated fruits were artificially wounded and inoculated with Penicillium expansum, Botrytis cinerea or Rhizopus stolonifer spore suspension (1 × 10⁵ spores mL^?1) and then incubated at 20 °C for 6 days. MeJA treatment significantly reduced the postharvest diseases. Incubation for 12 h was the optimal length of time after MeJA treatment, resulting in the lowest disease incidence and lesion diameter for all pathogens. The activities of defence enzymes including chitinase, β‐1,3‐glucanase, phenylalanine ammonia‐lyase, polyphenol oxidase and peroxidase were enhanced by MeJA treatment, and the level of total phenolics in MeJA‐treated fruit was also higher than that in control fruit. In addition, MeJA affected hydrogen peroxide (H₂O₂)‐metabolising enzymes such as superoxide dismutase, catalase and ascorbate peroxidase and induced a higher level of H₂O₂ during incubation, which might serve as a signal to induce resistance against P. expansum. CONCLUSION: MeJA was effective in reducing decay and might enhance disease resistance in peach fruit by increasing levels of antipathogenic proteins and antimicrobial phenolic compounds. Copyright © 2009 Society of Chemical Industry