Postharvest Melatonin Application Preserves Quality and Imparts Chilling Tolerance in Peaches

Peach being a climacteric fruit has a limited shelf life. Cold storage of peaches is an essential measure to maintain their quality. However, prolonged exposure to cold temperatures causes chilling injury in peaches, resulting in significant economic losses. Approximately, 40% of the produced commodity is lost in postharvest handling in which chilling injury contributes to about 25%. Melatonin can be a green solution and plays a key role in protecting peaches from chilling injury. Therefore, this experiment aimed to determine the effect of melatonin on the "Silver King"peaches by dipping them in 100 μM melatonin for 2 hours followed by storing them at chilling temperatures of 2 ± 1°C and 90-95% relative humidity for 21 d. The results showed that while control fruit experienced chilling injury and poor fruit quality, increased respiration rate, and enhanced senescence, 100 μM melatonin treatment was successful in preserving the fruit quality at chilling temperatures and was associated with the delayed respiration rate and lower malondialdehyde levels, along with the preservation of certain physicochemical parameters, namely, total soluble solids, pH, fruit firmness, and titratable acidity. Moreover, a 1.5 times higher proline concentration was observed in melatonin-treated peaches when compared to that of nontreated peaches. This rise was linked to the enhanced activity of Δ1-pyrroline-5-carboxylate synthetase and ornithine-δ-aminotransferase along with a decrease in the activity of proline dehydrogenase during 21 d of storage.