Abstract: In order to reveal the mechanisms of methyl jasmonate（MeJA）inhibiting postharvest decay in grape berries，‘Kyoho’grape berries were pretreated with 10 μmol · L-1 MeJA vapor for 6 h and then stored at 1 ℃ for 28 days. The fruit decay incidence，weight loss rate，levels of endogenous signaling molecules nitric oxide（NO）and hydrogen peroxide（H2O2），activities of phytoalexin synthesis related enzymes and individual phytoalexin compounds contents were determined at 7-day intervals during the storage. The results exhibited that the MeJA treatment could significantly inhibit the increase in decay incidence and weight loss rate，promote endogenous NO release and H2O2 content during the early stage of the storage，and simultaneously induce the increase in activities of phenylalanine-ammonia-lyase（PAL）， cinnamate 4-hydroxylase（C4H），4-coumarate coenzyme A ligase（4-CL）and resveratrol synthase（RS） associated with phytoalexin synthesis and the contents of phytoalexins including resveratrol and viniferin in grape berries during the storage. Therefore，we speculate that MeJA might play an important role in signal transduction in grape cells，which regulated the downstream signaling molecules NO and H2O2 levels to enhance activities of enzymes related to phytoalexin synthesis，resulting in promoting phytoalexin.accumulation and furthermore improving disease resistance in grape berries.

Key words: grape, methyl jasmonate, nitric oxide, hydrogen peroxide, phytoalexin