Antifungal lipopeptides from the marine Bacillus amyloliquefaciens HY2-1: A potential biocontrol agent exhibiting in vitro and in vivo antagonistic activities against Penicillium digitatum

This study aimed to clarify the antifungal activity and action mechanism of the lipopeptides from a marine Bacillus amyloliquefaciens HY2-1 against Penicillium digitatum both in vitro and in vivo. Results showed that HY2-1 lipopeptides exerted obvious inhibitions on spore germination and mycelium growth of P. digitatum. Furthermore, HY2-1 lipopeptides caused the aggravated lipid peroxidation, the decreased ergosterol biosynthesis, and the increased nucleic acid and protein leakage in P. digitatum, suggesting the damaged membrane integrity and permeability of P. digitatum. In addition, HY2-1 lipopeptides induced ROS burst and reduced the activities of antioxidant superoxide dismutase and peroxidase in P. digitatum, indicating that the intracellular redox homeostasis of P. digitatum was disturbed. In vivo biocontrol experiments showed that HY2-1 lipopeptides could effectively reduce the occurrence of green mold disease in citrus fruits artificially inoculated with P. digitatum spores. Most significantly, 4.8 mg/mL of HY2-1 lipopeptides achieved 100% of biocontrol efficacy after 30 days of storage and increased significantly contents of total phenols and flavonoids in citrus peels, demonstrating that HY2-1 lipopeptides inhibited green mold disease by exerting their antifungal activities and triggering fruit defense responses. This study deepens the understanding of marine Bacillus lipopeptides in the biological control of postharvest diseases.