Exogenous melatonin maintains postharvest quality in kiwiberry fruit by regulating sugar metabolism during cold storage

Abstract

Melatonin plays a potential role in preserving the postharvest quality of fresh products. This study investigated the effect of exogenous melatonin on sugar metabolism and quality change in kiwiberries under cold storage. Our results showed that melatonin improved fruit appearance, increased total chlorophyll, carotenoid, and ascorbate accumulation, and inhibited firmness and weight loss during storage. In addition, melatonin treatment increased the ratio of fruit-soluble solids to acid and upregulated the content of sucrose, glucose, fructose, and soluble sugars by regulating the activities of SS, SPS, AI, and NI enzymes as well as their transcript levels. Melatonin application inhibited the activity of AL and upregulated the transcript levels of HK and FK genes to slow down the starch decomposition, thereby delaying the softening of kiwiberries during the storage. These results indicated that melatonin application after the harvest of kiwiberry could improve both the external and internal quality of the fruit and inhibit senescence by modulating sugar metabolism.