Melatonin: a new tool to increase yield and quality at harvest and to extend postharvest shelf-life of pomegranate

Pomegranate (Punica granatum L.) trees were preharvest treated with melatonin 0.1 mM along the developmental growth cycle. Five treatments were performed (each month after fruit set) and quality was evaluated at harvest and during postharvest storage. At harvest the application of melatonin significantly increased tree productivity with higher yield, number of fruit per tree, and average fruit weight. The content of sugars (glucose and fructose) and organic acids (malic, succinic and ascorbic acid) were higher in treated than in non-treated fruit at time of harvest. During the 60 days of postharvest storage, pomegranates treated with melatonin showed a reduction of weight loss and softening, which was attributed to delay in the postharvest ripening. With respect to bioactive compounds, total phenolics, total anthocyanins and total antioxidant activity (TAA) were significantly higher in melatonin-treated fruits. After 60 days of storage, total anthocyanins and TAA remained higher in treated pomegranates, while total phenolics did not change during storage. These results suggest that melatonin applied at preharvest induced higher pomegranate quality at harvest (increased yield) and a net increase of shelf-life during postharvest storage.