Screening and Genomic Analysis of Bacillus velezensis R12 as a Biocontrol Agent Against Fusarium oxysporum Causing Wilt in Longya Lily (Lilium brownii var. viridulum)

Longya Lily (<i>Lilium brownii</i> var. <i>viridulum</i>) bulb rot, a devastating soil-borne disease caused by <i>Fusarium oxysporum</i> f. sp. <i>lilii</i> (Fol L1-1), severely compromises yield and quality of this economically significant crop. In this study, strain R12 was isolated from the rhizosphere soil of asymptomatic Longya lily plants and identified as <i>Bacillus velezensis</i>. The strain significantly disrupted the spore germination and hyphal morphology of Fol L1-1. In pot experiments, R12 not only effectively suppressed disease development but also promoted plant growth, a trait potentially linked to its indole-3-acetic acid (IAA) production capacity. Genomic analysis revealed a 4,015,523 bp circular chromosome (46.42% GC content) harboring gene clusters for the synthesis of diverse secondary metabolites, including surfactin, fengycin, difficidin, and bacillibactin. These findings highlight the potential of <i>B. velezensis</i> R12 as a biocontrol agent and provide insights into its mechanisms for suppressing phytopathogens and promoting plant growth.