Wheat-associated Antagonistic Bacteria Exerts Biocontrol Activity Against Fungal Growth and Deoxynivalenol Production in Fusarium Graminearum.

Fusarium head blight (FHB), primarily caused by Fusarium graminearum, leads to severe contamination of wheat grains with the mycotoxin deoxynivalenol (DON), posing a significant threat to grain safety and quality. While chemical control remains common, its efficacy is increasingly challenged by fungicide resistance and potential stimulation of DON production. Biological control represents a promising alternative, yet the identification of effective antagonistic agents and elucidation of their mechanisms are still needed. This study evaluated the biocontrol potential of the endophytic bacterium Bacillus velezensis strain 6W1 against FHB and DON contamination. The crude antagonistic extract exhibited a clear dose-dependent inhibitory effect on the mycelial growth of F. graminearum. The EC₅₀ value was determined to be 210.79 µg/mL, and complete growth inhibition (100%) was achieved when the extract concentration reached 800 µg/mL. Likewise, DON biosynthesis was significantly suppressed in a concentration-dependent manner, with DON levels reduced to 0 at 800 µg/mL of the crude extract.Furthermore, macrolactin A was identified as the core antagonistic compound responsible for the observed antifungal activity. A field trial confirmed that strain 6W1 application significantly reduced FHB severity and DON accumulation in wheat grains. These findings demonstrate the potential of B. velezensis 6W1 as an effective biocontrol agent against FHB and provide a theoretical basis for its application in managing DON contamination.