| The “Jin tian mi” muskmelon fruit were taken as the test materials in this article. Beginning with thecontrolled the postharvest diseases and induced disease resistance of muskmelon fruit, the effects ofstorage quality, reactive oxygen metabolism, disease resistance, physiology and metabolism, ripening andsoftening of muskmelon fruitsduring storage by pre-harvest salicylic acid treatment were studied.Studidedthe improving mechanisms of postharvest disease resistance on muskmelon by pre-harvest salicylic acidtreatment, and provided some theoretical basis for the control of postharvest muskmelon diseases.（1）Plants of muskmelon were sprayed with0.2mmol/L、1.0mmol/L and5.0mmol/L of salicylicacid at four times of plant melon: young fruit period, fruit enlarging period,netting period and48h beforepicking,respectively. Post-harvest melon were storaged at low temperature（7±1℃，RH85%）, the firmnessof fruits, weight-loss rate, soluble solids, titratable acid, incidence of disease, lantent infection rate ofmuskmelon, disease index and lesion area of muskmelon fruit inoculated with Alternaria alternate weremeasured regularly. The results showed that the firmness of melon fruit was keeping well; the increasing ofweight loss rate, the degradation of soluble solids, titratable acid were inhibited efficiently by1.0mmol/Lof salicylic acid treatment. Besides, the lantent infection rate of muskmelon were inhibited, the incidenceof disease and disease index of muskmelon were reduced efficiently; the lesion area of muskmeloninoculated with Alternaria alternate were inhibited by1.0mmol/L salicylic acid treatment. It could beenconcluded that1.0mmol/L salicylic acid treatment is the optimal concentration to keep the quality andimprve the disease resistance of muskmelon frults effectively.（2）The signal molecule of hydrogen peroxide’s (H2O2) content in muskmelon’s fruit wasaccumulated in early time pre-harvest, which was treated by1.0mmol/L of salicylic acid; in addition, thedefense responses of muskmelon was activated. Enhaced the activities of superoxide dismutase (SOD)hydrongen peroxide enzyme (CAT),, peroxidase enzyme (POD), ascorbate peroxidase enzymes (APX)and glutathione reductase(GR); improved the content of ascorbic acid and glutathione(GSH); reduced theproduction rate of O·2radical and the content of H2O2in late storage.The results showed that the activitiesof Phenylalanine AmmoniaLyase(PAL), Polyphenol oxidase(PPO), Chitinase(CHT) and β-1,3-glucanase(GLU) were enhanced; the accumulation of total phenols, flavonoids, and lignin content ofthe treated muskmelon by1.0mmol/L salicylic acid were effectively higher than that of the control in thelate storage. Thereby, the dieases resistance of muskmelon was improved.The respiration rate, ethylene production and ACC accumulation were reduced efficiently by1.0mmol/L of salicylic acid pre-harvest treatment; The1.0mmol/L of salicylic acid pre-harvest treatmentdelayed the peak of ACC synthase activity14days, suppressed the peak emergence of ACC oxidase (ACO)activity and reduced its activity effectly in late storage, inhibited the rising of MDA content and themembrane permeability, thus, it could delay the ripening and softening senscene of muksmelon fruit.Besides, the1.0mmol/L of salicylic acid treatment improved the firmness and protopectin’s content ofharvest muskmelon fruit; inhibited the activity of pectinase (PG), cellulose enzyme (Cx), and β-glucosida-se enzyme; decreased the original pection and cellulose degradation rate and slowed down the rise of thesoluble pectin content.Thereby, the salicylic acid treatment could inhibit the declining of firmness and thedeclining of fruit ripening softening. |
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