Studies On The Mechanism Of Improving The Resistance Of Postharvest Muskmelons With Chitosan Oligosaccharide And Salicylic Acid

The active oxygen metabolism and the metabolism of benzene propane play a very important role in improving the resistance of the fruit and ensuring the quality of the fruit.In order to explore the chitosan oligosaccharide?COS?,salicylic acid?SA?treatment effects on the storage quality,active oxygen metabolism,phenylpropanes metabolism of postharvest muskmelon,based on the"Xizhoumi 25"muskmelon as test material,through the determination of relevant indicators of quality,active oxygen metabolism,phenylpropanes metabolism and on the study of COS and SA treatment on increasing resistance of postharvest muskmelon related mechanism,in the hope of providing the theoretical reference for the application of SA and COS treatment in postharvest storage of muskmelon.?1?The muskmelon fruit was divided into two groups,one group were treated with 0.05g/L,0.5 g/L,5 g/L chitosan spraying concentration for fruit surface,spraying with distilled water as control;another group were treated with the concentration of 0.5 mmol/L,1 mmol/L,5 mmol/L salicylic acid were soaked for 10 min,the treatment of distilled water as control,then taken out and dried,storaged at?5±1??and 85%RH conditions.The natural incidence,hardness,soluble solids content,soluble solids contents,soluble solids contents,ascorbic acid,respiration,and ethylene production were measured every 7 days.The results showed that 0.5g/L COS and 1 mmol/L SA treatment could inhibit the muskmelon fruit soluble solids,titratable acid,ascorbic acid content decreased and decreased the respiration and ethylene production,good firmness,reduce the incidence rate of muskmelon fruit,so as to improve the quality and prolong the shelf life of muskmelon fruits.?2?COS,SA treatment can improve the muskmelon fruits in the early storage of hydrogen peroxide?H2O2?content to start a series of defense responses of fruit,improve the antioxidant system of fruit enzyme activity,decreased superoxide anion?O₂^-·?content.The test results show that 0.5 g/L COS and 1 mmol/L SA treatment can improve the content of H2O2 in the early storage,induction of superoxide dismutase in Muskmelon Fruit?SOD?activity,peroxidase?POD?activity and polyphenol oxidase?PPO?activity and catalase?CAT?had a certain activity,reduce the content of O₂^-·,0.5 g/L COS and 1 mmol/L SA treatment can improve the antioxidant defense system by ripening fruit enzyme activity in delaying fruit,and enhance disease resistance of fruit.?3?The phenylpropanoid metabolic pathway enhanced can cause adverse external environment of invasive plants and microorganisms to make a series of defense responses,while COS and SA increased can induce Phenylpropanes metabolism related enzymes and antimicrobial phenolic compounds,flavonoids content.The results of this study showed that0.5 g/L COS and 1 mmol/L SA treatment could significantly enhance the muskmelon fruit of phenylalanine ammonia lyase?PAL?and chitinase?CHT?and?-1,3-glucanase?GLU?activity,and can obviously promote the muskmelon fruit total phenolics,flavonoids,lignin content accumulation,COS,SA the fruit can enhance the resistance through the regulation of phenylpropanoid metabolic pathway.