Postharvest melatonin dipping maintains quality of apples by mediating sucrose metabolism

Senescence is a pivotal factor that causes quality breakdown and economic loss of fruit after harvest. In this study, 'Golden Delicious' apples were used as the materials to investigate the effect of melatonin dipping on quality parameters and sucrose metabolism during room temperature storage. Postharvest melatonin treatment inhibited respiratory intensity and ethylene release, increased flesh firmness, soluble sugar, ascorbic acid, and soluble solid contents, and titratable acid in apples. Furthermore, melatonin treatment inhibited acid invertase and neutral invertase activities, increased sucrose synthase and sucrose phosphate synthase activities, and repressed the activities of sorbitol dehydrogenase, sorbitol oxidase and sucrose synthase cleavage in apple fruit. All these findings suggest that exogenous application of melatonin could maintain quality of 'Golden Delicious' apples by mediating the enzyme activity in sucrose metabolism.