Effects of pre-harvest application of methyl jasmonate on quality and physiological characteristics of pitaya

【Objective】 The purpose of this study was to explore the effects of preharvest methyl jasmonate(MeJA) treatment on the harvest quality, storability and physiological characteristics of pitaya, and to provide technical support for the application of MeJA to improve the quality and storability of pitaya fruit.【Method】 Taking Zihonglong pitaya as material, five kinds of MeJA concentration gradients(0, 50, 100, 200, 400 μmol/L) were used to spray pitaya 8 days before harvest. Investigated the harvest yield, single fruit weight, first-class fruit rate, commercial fruit rate and diseased fruit rate.By observing and comparing the changes of decay time and decay rate after harvest, the changes of quality and physiological characteristics during storage of the control(0 μmol/L) and the best treatment was determined.【Result】 Under the experimental conditions, spraying MeJA before harvest had no significant effect on the yield per hectare and single fruit weight of pitaya(P>0.05). But, 100 μmol/L MeJA treatment improved the harvest marketability of pitaya, the first-class fruit rate and commercial fruit rate were significantly increased by 52.37% and 104.38%, respectively(P<0.05, the same below), and the rate of diseased fruit was reduced by 49.47%. During storage at room temperature, decay occurred 1 d later sprayed by 100 μmol/L MeJA before harvest than the control, and the decay rate was always lower than that of the control.Maintained higher intrinsic qualities such as soluble solids, soluble sugars and titratable acid during storage. The contents of polyphenols, total antioxidant capacity and activities of polyphenol oxidase(PPO), peroxidase(POD), β-1, 3-glucanase(GLU), chitinase(CHT) and phenylalnine ammonialyase(PAL) were significantly increased by 100 μmol/L MeJA treatment. The maximum difference of enzyme activity occurred before and after the beginning of decay. PPO, POD and CHT activities had the maximum values at the 6^th d of storage, which were increased by 33.13%, 140.38% and 207.16% than the control, respectively. PAL and GLU had the maximum values at 9^th d of storage, which were increased by 83.38% and 25.29% than the control, respectively.【Conclusion】 Spraying appropriate concentration of MeJA before harvest can reduce the susceptible rate of pitaya in growth period, improve the commercial fruit rate, maintain the storage quality, improve the antioxidant capacity and disease resistance during storage, so as to delay the fruit aging and control the occurrence of decay during storage, and prolong the storage period. The best treatment was 100 μmol/L.