Bacillus velezensis BN suppresses Fusarium tricinctum-induced lily wilt disease through multiple biocontrol mechanisms

Lily wilt caused by Fusarium tricinctum severely constrains the production of lily (Lilium davidii var. unicolor), and effective, sustainable control strategies are urgently needed. In this study, Bacillus velezensis strain BN was shown to suppress lily wilt disease through multiple biocontrol mechanisms. In vitro, cell-free filtrates of BN exhibited strong antifungal activity by significantly inhibiting mycelial growth and spore germination, with conidial germination inhibition reaching 87.6% at a filtrate concentration of 50% (v/v), while also inducing hyphal swelling and lysis and disrupting membrane integrity. Under greenhouse conditions, preventive application of BN provided more effective disease suppression than curative treatment. GFP labeling confirmed that BN could stably colonize lily roots, supporting its persistence in the rhizosphere. In addition, BN treatment significantly enhanced host defense responses, as evidenced by increased activities of catalase (CAT), peroxidase (POD), polyphenol oxidase (PPO), and phenylalanine ammonia-lyase (PAL). Metagenomic analysis further revealed that BN application reshaped the rhizosphere microbial community, enriching beneficial bacterial taxa and functional pathways related to carbon metabolism, secondary metabolite biosynthesis, and plant–microbe interactions. Together, these results indicate B. velezensis BN functions as a multifaceted biocontrol agent by simultaneously antagonizing the pathogen, enhancing host immune responses, and modulating a disease-suppressive rhizosphere microbiome, highlighting its potential for sustainable management of lily wilt disease.