Effect Of Postharvest Hot Water Dipping Treatment On Induced Resistance And Storage Quality Of Muskmelon Fruit

Muskmelons (Cucumis melo L.) are major economic crops in northwestern of China, and postharvest decay of fruit is serious. Chemical controls are used to reduce postharvest decays; however, fungi are becoming more resistant to fungicides and chemical residues and environmental concerns. In this study, muskmelons (cv. Yujinxiang) fruit were dipped in hot water at 53℃for 3 min to study if the treatment induces resistance and affect storage quality of fruit. The results indicated as follow:1. HWD under different conditions affected the lesion diameter of fruits inoculated with Trichothecium roseum. The treatment at 53℃for 3 min effectively reduced the lesion diameter of fruits. Higher temperature and longer time failed to promote better resistance and caused thermal damage. Moreover, fruits treated at 53℃for 3 min resulted a lower natural incidence of fruit during storage.2. The treatment increased phenylpropanoid pathway in fruits. The activity of key emzymes of the pathway was enhanced notablely as phenylalanine ammonia-lyase (PAL), 4-hydroxy-cinnamic acid (C4H) and 4-coumarate COA ligase (4CL). The accumulation of antifungal compounds was increased notablely as cinnamic acid, coumaric acid, caffeic acid, ferulic acid, phenolic, flavanoid and lignin. And the activity of peroxidase (POD) and polyphenoloxidase (PPO) was increased by the treatment.3. The treatment effectively maintained cell wall structure of fruit and the content of propectin and cellulose, reduced the water soluble pectin content, promoted the accumulation of hydroxyproline-rich glycoprotein (HRGP), and suppressed the activity of pectinesterase (PE), polygalacturonase (PG), cellulase (Cx),β-glucosidase (BG) of fruits.4. The treatment noticeably accumulated the suberin and callose content, decreased the dirt particles on the surface of fruits, melted the epicuticular waxes and then covered and sealed the stomata, reduced the cells interval, tighted the tissues of fruit cortexes.5. The treatment effectively inhibited the ethylene production and weight loss, maintained SSC, TA, firmness and colour. The treatment inhibited aroma formation of fruit, delayed the release of acetic acid ester and charctristic aroma compounds, and improved the evaluated sensory quality of fruits.In conclusion, postharvest HWD treatment reduced the incidence of postharvest diseases by inducing resistence of fruits in enhancing phenylpropanoid pathway, restraining the ethylene production, maintaining the cellwall structure, changing the peel structure. Moreover, HWD treatment maintained the storage quality of fruits.