Preservative effects of clove extract against Alternaria alternata on postharvest strawberries and associated shifts in microbial communities

Introduction Strawberries are highly perishable postharvest due to infection by pathogens such as Alternaria alternata , and chemical fungicides have drawbacks like residues and resistance. Clove extract exhibits broad-spectrum antimicrobial activity, but its targeted inhibitory threshold and mechanism on strawberry postharvest pathogens remain unclear. Methods The minimum fungicidal concentration (MFC) of clove extract against A. alternata was determined. “Benihoppe” strawberries were treated with MFC (30 mg/mL) and stored at 25°C/90% RH. Key quality indicators (firmness, VC content, weight loss rate, etc.) were monitored, and microbial community structure was analyzed via high-throughput sequencing. Results The MFC of clove extract against A. alternata was 30 mg/mL, which reduced spore survival rate to 40.0% and increased cell membrane permeability. After 8 days of storage, the treatment group showed 68.3% higher firmness, 52.5% higher VC content, and 46.4% lower weight loss rate than the control. The abundance of spoilage microorganisms (e.g., Alternaria , Pantoea) decreased, while beneficial bacteria (e.g., Bacillus ) increased in the treatment group. Discussion Clove extract preserves strawberries by directly damaging the cell membrane of A. alternata and reshaping the fruit surface microbial community, providing a green alternative for postharvest preservation.