Effect of exogenous melatonin in fruit postharvest, crosstalk with hormones, and defense mechanism for oxidative stress management

Derived from tryptophan, melatonin (MT; N‐acetyl‐5‐methoxytryptamine) is a ubiquitous indoleamine that is widely distributed in species ranging from microorganisms to mammals. It has been associated to play vital roles in the human body like cardiac rhythms, immunological enhancement, and antioxidant activity. In plants, it is a pleiotropic molecule with multiple roles, as it not only performs extensive functions like delaying senescence, growth and development regulation, exerting antioxidant effects, and facilitating adaption of plants to certain biotic and abiotic stress responses but also provides resistance to chilling injury and disease development. This paper reviews the latest progress in the multiple roles of MT in fruits, summarizes the pathways for its biosynthesis, and presents the relation of MT with plant hormones, like auxin, cytokinin, ethylene, gibberellins, abscisic acid, jasmonic, and salicylic acid, and highlights the effect of postharvest application of MT on physiology and quality of fruits, action mechanisms, and safety regulations of MT. Recent trends focus on using alternatives that are safe for postharvest produce and do not have major side effects. MT is a better alternative to hazardous chemicals being commercially used in the postharvest management of fruits and providing future directions for its utilization.