Strain prioritization for lipopeptide-producing bacteria with antagonistic effects against Fusarium graminearum

The phytopathogenic fungus Fusarium graminearum causes severe plant disease such as wheat scab and poses threats to human health by mycotoxin contamination. Green agriculture's rise has brought growing attention to biological control methods, which contributes to pesticide reduction. In this study, we employed a quantitative reverse transcription PCR (qRT‒PCR) based high-throughput screening method to identify bacterial strains that produce lipopeptides. By using this method, we identified Bacillus amyloliquefaciens strain 7D3, which exhibits high lipopeptide production and strong antifungal activity. The crude extract of 7D3 fermentation broth exhibited an EC₅₀ of 75.09 ± 6.72 μg/mL. Analysis of the metabolites via liquid chromatography time-of-flight mass spectrometry (LC-TOF-MS) revealed numerous lipopeptides, such as surfactin and iturin. The strain inhibited Fusarium graminearum infection by disrupting the cell membrane, thus damaging the mycelial structure of the fungus and resulting in disordered hyphal osmotic characteristics and eventually hyphal rupture. This strain also inhibited sporulation as well as germination of Fusarium spores. Additionally, greenhouse trials demonstrated that the 7D3 strain effectively suppressed Fusarium infection in wheat while also inhibiting the accumulation of mycotoxins. This study provides an alternative method for screening biocontrol agents with activity against FHB.