The Effect of SO₂ Pulse on Synergistic Interaction of Postharvest Quality and Fungal Community During Thin-Skinned...

SO₂ is commonly used to control postharvest grape mold, but the technology of low-residue usage and the regulatory effects on the grape microbial community are still to be explored. In this research, slow-release SO₂ pads (SR) and intermittent high SO₂ pluses (IHP) were adopted to treat Daqing grapes during low-temperature storage. The results showed that IHP maintained the best appearance, grape-skin integrity, and reduced the SO₂ residue by 49.9% compared to SR group. Meanwhile, the grapes of IHP significantly reduced the decay, inhibited the browning and weight loss, and maintained higher firmness than the control. To explain the reason, the activities of enzymes associated with the immune resistance system, including superoxide dismutase (SOD), peroxidase (POD), phenylalanine ammonia (PAL), and polyphenol oxidase (PPO) were found a higher level in IHP during storage. More importantly, changes in fungi communities were analyzed using internal transcribed spacer (ITS) in the IHP and control groups. The changes in fungal communities showed that IHP preserved the richness of OTU and diversity of fungi communities, effectively inhibiting the relative quantity of the primary pathogens: B. cinerea, C. chasmanthicola, and A. alternata. Furthermore, correlation analysis suggested that microbial communities and immune resistance independently regulate grape postharvest quality while being interrelated, collectively influencing the postharvest quality of Daqing grapes and forming "short-term stress-grape immune resistance (the postharvest quality)-the postharvest grape surface microbiome" a novel interaction system. Thus, we inferred that IHP could induce grape resistance, inhibit surface pathogens, modify surface microbiome, and maintain the postharvest quality of the grapes.