Studies on the Control of Postharvest Diseases of Muskmelons and the Induction of Resistance Related Enzymes and Defense Substances by Salicylic Acid Treatment

The enzymes activity related muskmelon disease resistance by salicylic acid treatment in pro-harvest muskmelon fruits was investigated in this paper. The plants of “Jin tian mi” muskmelon as test materials, muskmelons were sprayed at four growing seasons: young fruit period (two weeks after flowering), ruit enlarging period (three weeks after flowering), netting period (four weeks after flowering) and 48 h before picking by the 1.0 mmol/L salicylic acid solution, respectively. The harvest fruits were storage at 7°C after precooling. The incidence of disease, disease index; the content of total phenols, flavonoids and lignin of muskmelon, CHT, GLU and PAL activities of muskmelon were measured during the storage every 7 days. The results showed that: compared with the control, the disease time of muskmelon was delaywd, fruit disease incidence and disease index were decreased, chitinase and β-1,3-glucanase were induced, phenylalanine ammonia lyase activity was increased, and the total phenolic, flavonoid, lignin content were better maintain by 1.0 mmol/L salicylic acid treatment. It is suggested that the increase of the related enzymes activity induced by salicylic acid were closely related to the increase of disease resistance in pro-harvest muskmelons.