Effects of Sulfur Dioxide on Disease Resistance and Storage Quality of Durian (Durio zibethinus L.): A Comprehensive Analysis Integrating GC-IMS, HTS, Physiological and Biochemical Parameters

In this study, we examined the multifaceted effects of sulfur dioxide (SO2) on the postharvest preservation of durian and the underlying potential mechanism of disease resistance. Our results show that 2% SO2 preserved the good quality of durian by inhibiting its respiration rate and ethylene production (day 15), reducing weight loss, and maintaining color, firmness, and ascorbic acid content. Furthermore, the volatile organic compounds (VOCs) were investigated further by gas chromatography-ion mobility spectrometry (GC-IMS). Ester compounds (fruity aroma of durian) were primarily intensified in SO2-treated samples, while SO2 weakened the content of volatile sulfur compounds. Certain antioxidant and antifungal VOCs, including alpha-terpinene, benzyl alcohol, 2-decanone, and 2-heptylfuran, may contribute to enhancing the disease resistance of durian. High-throughput sequencing (HTS) analysis indicated that SO2 may enhance the disease resistance of durian by shifting the fungal community succession, which stabilized the relative abundance of Meyerozyma sp. and decreased the relative abundance of Alternaria sp. (on day 5), Verticillium sp. (on day 5), and Moesziomyces sp. (on day 5 and 10). Additionally, SO2 induced the activities of defense-related enzymes, such as catalase (CAT), polyphenol oxidase (PPO), peroxidase (POD), chitinase (CHI), and β-1,3-glucanase (β-GLU), which may synergize with antifungal VOCs and fungal community succession to enhance durian disease resistance. These results clarify the potential distinct mechanisms of disease resistance of SO2 and provide a scientific basis for the application of SO2 in the postharvest preservation of durian fruits.