Melatonin treatment delays senescence and alleviates chilling injury in spaghetti squash during low-temperature storage

In this study, the effects of 0.2 mmol L-1 melatonin (MT) treatment on the senescence, chilling injury (CI), and the AsA-GSH cycle of spaghetti squash during storage at 4 degrees C and 65-70% relative humidity were investigated. The results demonstrated that the MT treatment delayed the spaghetti squash senescence since a reduction in the CI index, respiration rate, and total soluble solids content was observed. Furthermore, the degradation of color was inhibited. Moreover, a significant increase in the MT treatment was detected in the biological activities of catalase, superoxide dismutase, and peroxidase, reducing the accumulation of superoxide anion and hydrogen peroxide. Additionally, the MT treatment enhanced the AsA-GSH cycle since an up-regulation was detected in some biological parameters, including ascorbate peroxidase, monodehydroascorbate reductase, dehy-droascorbate reductase, glutathione peroxidase, and glutathione reductase. This increase led to ascorbic acid and glutathione accumulation, enhanced the ratio of AsA/DHA and GSH/GSSG, and maintained higher cellular redox levels. Overall, the results suggested that MT treatment conferred resistance to cold in spaghetti squash by enhancing the AsA-GSH cycle, improving the antioxidant capacity, and ultimately alleviating chilling injury during cold storage.