Antagonistic Activity and Genomic Insights of Bacillus velezensis JE250 against Erwinia amylovora

Fire blight, caused by Erwinia amylovora, is a highly destructive bacterial disease that affects apple and pear orchards worldwide, leading to significant economic losses. In this study, we isolated and characterized endophytic bacterial strains from apple trees in Gyeongsangbuk-do, South Korea, to identify potential biocontrol agents against E. amylovora. Among the five antagonistic strains identified, Bacillus velezensis JE80 and JE250 exhibited the strongest inhibitory effects. Further analysis using culture filtrates (CFs) from these strains demonstrated that the CFs of JE80 and JE250 not only suppressed E. amylovora growth in a growth-phase-dependent manner but also significantly impaired bacterial motility and biofilm formation. Notably, in planta assays revealed that JE250 effectively reduced fire blight symptoms in apple blossoms, performing comparably to streptomycin sulfate. Whole-genome sequencing of JE250 identified biosynthetic gene clusters associated with the production of antimicrobial compounds, including difficidin, fengycin, bacillaene, macrolactin, bacillibactin, and bacilysin, further supporting its strong antagonistic potential. These findings suggest that B. velezensis JE250 is a promising biocontrol agent for sustainable fire blight management. Future research should focus on optimizing formulation methods for field application, characterizing specific antimicrobial compounds, and evaluating its long-term efficacy in orchard environments.