Insights into the roles of melatonin in maintaining quality and extending shelf life of postharvest fruits

Most of postharvest fruits are highly perishable, which limits greatly marketability and potential expansion. In recent years, significant progresses on understanding the role of melatonin in delaying senescence have been achieved while the melatonin as a postharvest alternative in maintaining quality and extending shelf life of postharvest fruit has been developed. This paper reviews the recent progresses in the multiple functions of melatonin, summaries the detection, content and synthesis of endogenous melatonin in postharvest fruit, discusses the possible mechanisms of melatonin in maintaining quality and extending shelf life of postharvest fruit, emphasizes the beneficial effects of the melatonin-related handling and provides the future research direction for postharvest alternative. The amount of melatonin in postharvest fruit is relatively low and affected greatly by many factors. The major precursors and genes of melatonin biosynthetic pathway have been identified in various fruits. Exogenous melatonin treatment not only delayed ripening, senescence and quality deterioration, but also enhanced disease resistance and chilling tolerance of postharvest fruit. The multiple biological functions of melatonin in postharvest fruit were attributed to the induction and interaction with reactive oxygen species and nitric oxide and coordination with plant hormones and other signaling molecules, which enhanced antioxidant and defense systems, reduced oxidative damage, and maintained energy of postharvest fruit.