Genomic and antifungal analysis of Bacillus velezensis CX-H3: a promising biocontrol agent for maize Fusarium root rot

Bacillus velezensis CX-H3, a plant growth-promoting rhizobacterium isolated from maize rhizosphere soil, demonstrates dual functionality by suppressing plant pathogens and enhancing maize health. Pathogenicity evaluation of 11 Fusarium species isolated from diseased maize roots identified Fusarium graminearum as the primary causal agent of maize Fusarium root rot. In vitro , antagonism assays demonstrated CX-H3's potent inhibition of F. graminearum mycelial growth (93.37 % inhibition rate), with greenhouse trials confirming a control efficacy of 58.64 % in root rot severity and significant improvement in seedling vigor. Genomic characterization revealed 13 biosynthetic gene clusters in CX-H3, including seven functionally annotated clusters responsible for antimicrobial metabolites: surfactin, fengycin, bacillaene, difficidin, macrolactin H, bacillibactin, and bacilysin. Targeted purification of surfactin homologs via semi-preparative reversed-phase high-performance liquid chromatography, coupled with structural elucidation using quadrupole time-of-flight mass spectrometry, identified surfactin C12 as the dominant antifungal variant. This lipopeptide achieved complete suppression of F . graminearum at a minimal inhibitory concentration of 25 μg ml −1 . These results establish CX-H3 as a biocontrol agent, synergizing its genomic potential for antimicrobial diversification with surfactin-mediated antifungal efficacy. The strain's combined capacity to directly inhibit pathogens and enhance plant vitality provides a sustainable strategy for reducing agrochemical reliance in maize cultivation. • Bacillus velezensis CX-H3, isolated from maize rhizosphere soil, demonstrates strong antagonistic activity against Fusarium graminearum , Fusarium verticillioides , and Fusarium proliferatum , effectively preventing maize Fusarium root rot disease. • Surfactins were identified as the primary active compounds in CX-H3 responsible for its potent antifungal activity against F . graminearum , with surfactin C12 exhibiting the most significant inhibition. • In greenhouse trials, B . velezensis CX-H3 significantly reduced sweet corn root rot incidence and severity, with a control efficacy of 58.64 %, outperforming traditional chemical agents.