Effects of treatments of different H₂S and NO concentrations on expressions of genes related to decay inhibition and antioxidation in strawberries during shelf life

【Objective】This study aimed to investigate the regulatory effects of hydrogen sulfide （H₂S） and nitric oxide （NO） gases on enzyme activities related to decay inhibition and antioxidation as well as related gene expression in strawberries during shelf life for screening the optimal treatment concentration， thereby providing technical support for postharvest preservation of strawberries.【Method】The strawberry cultivar Hongyan was used as the experimental material. For the fumigation treatments， H₂S and NO were applied separately at different concentrations （50， 100， 200， and 400 μL/L）， and samples not subjected to any gas fumigation were used as the control （CK）. The samples were stored at （20±0.5）℃ for 6 d， and the fruit decay rate， activities of superoxide dismutase （SOD）， catalase （CAT），peroxidase （POD），ascorbate peroxidase （APX），and polyphenol oxidase （PPO），as well as the related relative expression of key genes were determined during shelf life. Correlation analysis and principal component analysis were performed to comprehensively analyze the relationships among the measured indicators.【Result】Compared with CK，all H₂S and NO treatments inhibited decay and enhanced antioxidant capacity， and the 200 μL/L H₂S treatment exhibited the greatest effects. At the 5^th d of shelf life， CAT and APX activities reached 26.26 U/g and 50.89 U/（g·min），which were 2.02 and 4.72 times those of the CK. During the middle to late shelf life （4-6 d），the relative expression of FaSOD， FaCAT， FaPOD， and FaAPX was significantly up-regulated （P<0.05， the same below）， while FaPPO gene expression and PPO activity were inhibited， which effectively delayed oxidative damage and browning process. At the 6^th d of shelf life，the decay rate was only 24.25%， representing a decrease of 73.55% compared with the CK （91.67%）， which was lower than that under the NO treatment of the same concentration （33.30%）， and the fruit color remained well-preserved without obvious changes. Correlation analysis showed that the decay rate had extremely significantly positive correlations with the expression of FaSOD and FaPPO genes （P<0.01）. Comprehensive scores of principal component analysis indicated that， the 200 μL/L H₂S treatment exhibited the optimal performance across all indicators， as its comprehensive scores were the highest along the shelf life， proving it had the best comprehensive regulation effects.【Conclusion】The 200 μL/L H₂S treatment exhibits superior quality regulation capability for strawberries during shelf life and has good synergistic effects for activating the antioxidant system and delaying browning， so it can be an effective measure for extending the shelf life of strawberries.