Enhancing disease resistance in peach fruit with methyl jasmonate

BACKGROUND: Peaches are susceptible to microbial decay during postharvest distribution at ambient temperature. To search foreffectivealternativestocurrentlyusedfungicidesfordiseasecontrol,inthisstudytheeffectofmethyljasmonate(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 × 10 5 spores mL −1 )a nd 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 MeJAtreatment,andtheleveloftotalphenolicsinMeJA-treatedfruitwasalsohigherthanthatincontrolfruit.Inaddition,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 againstP.expansum. CONCLUSION:MeJA was effectivein reducing decay andmightenhancediseaseresistanceinpeach fruitby increasinglevelsof antipathogenic proteins and antimicrobial phenolic compounds. c � 2009 Society of Chemical Industry