Melatonin application suppresses oxidative stress and maintains fruit quality of cold stored 'Esperanza' raspberries by regulating antioxidant system.

Raspberries are highly perishable and have a short storage life. To extend its storage life, we evaluated the impact of preharvest melatonin (MEL) application (0, 50, 100, 200 µmol L−1), three days before harvest, on the activities of oxidative and antioxidative enzymes and quality attributes in 'Esperanza' raspberries up to 10 d cold storage. The 200 µmol L−1 MEL-treated raspberries exhibited a significant reduction in disease incidence while maintaining higher marketable fruit and activities of superoxide dismutase, glutathione reductase, dehydroascorbate reductase, monodehydroascorbate reductase, ascorbate peroxidase and catalase as compared to control. Additionally, it reduced activities of polyphenol oxidase, peroxidase and lipoxygenase enzymes and increased flavonoids and ascorbic acid levels. However, preharvest spray of 100 µmol L−1 MEL mitigated fruit weight loss and maintained higher anthocyanins, and glutathione than control. In conclusion, MEL application (100–200 µmol L−1), three days before harvest, supressed oxidative stress by maintaining higher activities of antioxidant enzymes in raspberries during 10 d of cold storage. • Preharvest MLT spray maintained fruit quality of raspberries during cold storage. • MLT suppressed H2O2 radicals, MDA and activities of LOX, POD and PPO. • MLT increased TPC, TAC, TFC and activities of CAT and SOD. • MLT treatment upregulated the AsA-GSH pathway in raspberries. [ABSTRACT FROM AUTHOR]