Melatonin treatment delays postharvest senescence and regulates reactive oxygen species metabolism in peach fruit

Peach fruit deteriorates and senesces quickly during storage at ambient temperature. Research confirms that melatonin (MT) is involved in plant senescence. However, little information is available on the effects of MT on postharvest senescence. In this study, two cultivars of peach fruit ‘Shahong’ and ‘Qinmi’ were treated with MT at 0.1 mmol L−1 and then stored at ambient temperature (25–28 °C)for 7 days. The results showed that MT treatment effectively slowed process of senescence in both peach cultivars, as indicated by reduced weight loss, decay incidence and respiration rate as well as maintained firmness, total soluble solids and ascorbic acid contents. MT treatment significantly enhanced the activities of superoxide dismutase, catalase, peroxidase and ascorbate peroxidase in both cultivars, but decreased the activity of lipoxygenase, levels of superoxide anion and hydrogen peroxide, and malondialdehyde content. These results indicate that the activation of antioxidant enzymes to scavenge superoxide anion and hydrogen peroxide by MT treatment was associated with the maintenance of membrane integrity, which might be a part of the mechanism implicated in delay of senescence in peach fruit.