Exogenous melatonin delays oxidative browning and improves postharvest quality of litchi fruits

Abstract

Litchi fruit is valued for its characteristic flavor and attractive color. However, oxidative pericarp browning soon after harvest limits its shelf-life and availability. Melatonin has been reported to mitigate several abiotic stresses in plant and plant based products. In this investigation, the effects of postharvest application of melatonin (0.1, 0.25, and 0.5 mM) on pericarp browning, shelf-life, and overall quality (weight and decay loss, TSS, ascorbic acid, total phenolic, flavonoid content, antioxidant activity, browning enzymes) of litchi fruit were determined during ambient storage. Fruits underwent to 0.5 mM melatonin treatment recorded reduced activities of PPO and POD thereby resulting in delayed oxidative browning in pericarp. This was coupled with reduced weight loss with higher retention of antioxidant compounds and potential in treated fruits during storage. The gene expression analyses revealed that postharvest melatonin application down-regulated expression of genes such as LcPOD and LcPPO and up-regulated anthocyanin related genes, such as LcUFGT and LcDFR those were linked to pericarp browning. In sum, results showed that exogenous melatonin (0.5 mM) could effectively preserve the postharvest fruit quality of litchi.