Metschnikowia Pulcherrima yeast T-2 VOCs Enhances Postharvest Blueberry Fruit Resistance to Botrytis cinerea by Activating Flavonoid Metabolic Pathways

The postharvest rot of blueberry fruits caused by Botrytis cinerea led to economic losses. Here, we found that volatile organic compounds (VOCs) emitted by Metschnikowia Pulcherrima T-2 reduced fruit rot. Nevertheless, the mechanism of VOCs induced fruit resistance remains unclear. The total flavonoids content in blueberry fruits were significantly higher by T-2 VOCs treatment. Metabolomic analysis unraveled that the contents of quercetin, kaempferol and myricetin were significantly higher with T-2 VOCs treatment. The quercetin, kaempferol and myricetin also inhibited growth of B. cinerea in vitro. According to transcriptome analysis, the expression level of VcNAC83 was significantly highly increased after T-2 VOCs treatment. Furthermore, VcNAC83 was highly correlated with rot rate and total flavonoids content, and RT-qPCR also verified that VcNAC83 was significantly up-regulated. Transient overexpression of VcNAC83 in fruits enhanced the resistance to B. cinerea, and reduced lesion diameter and rot rate. The total flavonoids content, expression levels of flavonoid-related genes such as PAL, F3H, F3'H, DFR and F3'5'H and contents of quercetin, kaempferol and myricetin were also increased in the overexpressed blueberry fruits. These results support a critical role for T-2 VOCs in blueberry immune response to B. cinerea, and provide a new method of postharvest storage.