Transcriptomic analysis reveals the resistance mechanism of flavonoids from Sedum aizoon L. to Rhizopus nigricans in postharvest strawberry fruit

Strawberry (Fragaria x ananassa) is one of the most popular fruits worldwide, rich in vitamins and with extremely high nutritional value. However, the postharvest diseases of strawberries caused by pathogenic fungi reduced the commercial value and caused serious economic losses. Rhizopus nigricans (R. nigricans) is one of the fungal pathogens causing huge economic losses and potential food safety problems. Flavonoids from Sedum aizoon L. (FSAL) is an herbal medicine reported to have fungicidal activity. In this study, strawberries were treated with FSAL, analyzed the incidence and fruit quality, and their antioxidant enzymes, such as ascorbate peroxidase (APX), catalase (CAT), polyphenol oxidase et al. (PPO), and peroxidase (POD). The results showed that exogenous FSAL treatment (especially at 30 h) enhanced strawberry resistance to R. nigricans, reduced disease incidence, maintained better fruit quality, and exhibited higher pathogen resistance-related defense enzyme activities. Further transcriptomic analysis of samples treated for 30 h revealed a total of 710 genes responsive to FSAL, and there were 510 and 200 genes identified as being substantially upregulated and downregulated, respectively. KEGG analysis indicated that FSAL treatment induced resistance in strawberry in relation to phenylpropanoid biosynthesis, glutathione metabolism, and amino acid metabolism-related changes. The results of this study may reveal the mechanism of FSAL-induced resistance in strawberry and provide new theoretical foundation for the safe and efficient control of postharvest diseases in strawberry.