Biocontrol potential and antifungal mechanism of a novel Bacillus velezensis NH-13–5 against Botrytis cinerea causing postharvest gray mold in table grapes

Botrytis cinerea is one of the most notorious postharvest diseases of table grapes. Frequent applications of synthetic fungicides have led to multi-fungicide resistance of B. cinerea , greatly promoting the exploration of biological strategies to control B. cinerea . In this study, Suaeda glauca -derived Bacillus velezensis NH-13–5 performed high environmental adaptability to salinity, pH, UV radiation and the presence of synthetic fungicides. Strain NH-13–5 showed in vitro and in vivo biocontrol potential against multi-fungicide resistant B. cinerea . Especially, its 10 % culture broth (1 ×10 8 CFU mL −1 ) exhibited good in vivo preventive effect against gray mold on table grapes, reducing the lesion diameter of 94.1 % and the disease incidence of 80 %, respectively. Bioassay-guided isolation and HRMS 2 elucidation had obtained two lipopeptide series, including C 15 /C 16 iturin A ( 1 and 2 ) and C 17 /C 18 fengycin A ( 3 and 4 ). However, only C 15 iturin A ( 1 ) and C 18 fengycin A ( 4 ) could significantly inhibit both spore germination and germ tube elongation, suggesting that lipid chain length could affect their antifungal potentials. Further research revealed that two lipopeptides could result in the loss of membrane integrity and abnormal accumulation of reactive oxygen species, causing obvious structure damage of mycelial cells as evidenced by scanning and transmission electron microscope. Finally, strain NH-13–5 also showed preservative potential for postharvest table grapes with higher quality parameters of vitamin C, titratable acid, soluble sugar and firmness. Acute oral toxicity test of strain NH-13–5 indicated that it belonged to the non-acute toxic level. This study provides a promising and safe biological agent to control gray mold on postharvest table grapes, and first revealed antifungal mechanisms of lipopeptides C 15 iturin A and C 18 fengycin A. • A new biocontrol strain of Bacillus velezensis NH-13–5 was obtained from Suaeda glauca . • Antifungal C 15 /C 16 iturin A and C 17 /C 18 fengycin A were isolated and elucidated. • Antifungal mechanisms of C 15 iturin A and C 18 fengycin A were first revealed. • Strain NH-13–5 showed good preservative potential for harvested table grapes. • Strain NH-13–5 belong to the non-toxic level due to oral safety evaluation.