Nitric Oxide Inhibits Postharvest Black Spot Disease in Prunes through the Regulation of Reactive Oxygen Species and Energy Metabolism

This study aimed to investigate the effect of nitric oxide(NO) treatment on the resistance of prunes to postharvest black spot disease. After harvest, Xinjiang-grown ‘France' prunes were subjected to vacuum infiltration (0.02 MPa for 2 min followed by atmospheric pressure for 8 min) using solutions of the NO donor sodium nitroprusside (SNP) at concentrations of 0.0125, 0.025, and 0.05 mmol/L, respectively. Thereafter, the treated fruits were wounded, inoculated with Alternaria alternata, and stored at (1.0 ± 0.5) ℃ and relative humidity of 90%–95% for 120 d. Samples were collected every 20 days to measure infection incidence, lesion diameter, superoxide anion radical production rate, hydrogen peroxide (H₂O₂) content, ATP and ADP levels, energy charge, and the activities of enzymes related to reactive oxygen species (ROS) and energy metabolism. The results indicated that NO treatment suppressed infection incidence and lesion expansion in prunes, with the most effective treatment being 0.025 mmol/L NO. Compared with the control group, infection incidence and lesion diameter at the end of storage were reduced by 27.89% and 33.73%, respectively (P < 0.05). NO treatment enhanced the activity of superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) in prunes, and significantly suppressed the decline in the activities of succinate dehydrogenase (SDH), cytochrome c oxidase (CCO), H⁺-ATPase, and Ca²⁺-ATPase during storage, while inhibiting the production of superoxide anion radical and H₂O₂. It maintained higher ATP and ADP levels and energy charge in prunes, suppressed the increase in malondialdehyde (MDA) content, and maintained the balance between intracellular ROS production and scavenging, thereby effectively enhancing prune resistance to black spot disease.