Isolation and Identification of Antifungal Polyketones from Bacillus velezensis DJ1 and Their Biocontrol Potential Against Corn Stalk Rot

Corn stalk rot, caused by <i>Fusarium graminearum</i>, severely threatens corn production, while chemical fungicides lead to resistance and environmental risks. Thus, exploring environmentally friendly biocontrol agents is crucial. Though <i>Bacillus</i> polyketones have antifungal activity, their active components, corn stalk rot biocontrol potential and rhizosphere impacts remain unclear. This study isolated polyketones from <i>Bacillus velezensis</i> DJ1, assessed their antifungal activity and mechanism against <i>F. graminearum</i>, verified greenhouse efficacy, analyzed rhizosphere microbiota, and identified active components via HPLC-HDMS Q-TOF. The results showed that DJ1 polyketones showed dose-dependent inhibition by disrupting <i>F. graminearum's</i> mycelium and membrane, with 44.33% greenhouse control efficacy. They did not disturb rhizosphere balance, only increasing Bacteroidota and <i>DYGX01,</i> and the active components were difficidin and bacillaene. These findings confirm DJ1 polyketones as promising eco-friendly biocontrol agents, providing a new strategy for sustainable corn stalk rot management.