Regulation of Reactive Oxygen Species and Cell Wall Metabolism in ‘Huangmengcui’ Muskmelon by Storage Temperature

Muskmelon (Cucumis melo L.) is an important cash crop primarily cultivated in the Xinjiang region, and its flesh is sweet, crisp, and juicy with a pronounced aroma. However, postharvest quality deterioration in muskmelons is associated with physiological and biochemical processes, including oxidative stress caused by the accumulation of reactive oxygen species (ROS) and the enzymatic degradation of cell wall components. These processes can compromise membrane integrity, reduce fruit firmness and nutritional quality, and consequently shorten shelf life. Temperature control has been widely used to maintain fruit quality, and low-temperature storage is a key approach for slowing ripening and extending shelf life; nevertheless, better storage temperature is highly cultivar-specific. Therefore, this study stored muskmelons at 4 °C, 10 °C, and 20 °C for 28 days, aiming to determine the effects of different storage temperatures on their quality. The results showed that, on day 28 of storage, 10 °C significantly upregulated the genes encoding superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), and peroxidase (POD), and enhanced the corresponding enzyme activities, thereby boosting ROS scavenging and reducing membrane lipid peroxidation. Concomitantly, 10 °C downregulated the genes encoding cell wall-degrading enzymes, including pectin methylesterase (PME), polygalacturonase (PG), pectin lyase (PL), β-galactosidase (β-gal), and β-glucosidase(β-glu), and inhibited their activities, thereby preserving protopectin and cellulose. On day 28 of storage, the 10 °C treatment exhibited the lowest weight loss (4.37%), maintained the highest firmness (2.67 N), and retained higher contents of total phenolics and vitamin C. In summary, storage at 10 °C maintained the postharvest quality of muskmelon by inhibiting cell wall degradation and affecting reactive oxygen species metabolism.