Melatonin treatment reduces ethylene production and maintains fruit quality in apple during postharvest storage.

The effects of treatment with melatonin on ripening of 'Fuji' apples during storage at 1 °C for 56 d were investigated. The apples were harvested at the commercial ripening stage and treated with 1 mmol L-1 melatonin. Compared with the control, melatonin treated apples had significant reduced ethylene production (28 d-56 d) and weight loss (14 d-56 d) during storage (p < 0.05). Also, the melatonin treatment maintained better apple skin structure throughout storage. The reduced ethylene production was regulated by the decreased expressions of MdACO1, MdACS1, MdAP2.4 and MdERF109, based on RNA-Seq analysis, which was validated using qRT-PCR analysis. Moreover, the activity of 3 enzymes, including peroxidase (POD), superoxide dismutase (SOD) and catalase (CAT), were significantly increased in melatonin treated fruit (p < 0.05). Taken together, this study highlights the inhibitory effects of melatonin in ethylene biosynthesis and factors influencing postharvest quality in apple.