P-049 - 3-Methyl-Pentanoic Acid from Plant Endophytic Bacterium Bacillus safensis: A Novel Soil Biofumigant and Biocontrol Agent of Fungal Diseases

Soilborne and foliar fungal pathogens threaten global food security, exacerbated by the lack of effective fumigants following the methyl bromide ban. Here, we report 3-methylpentanoic acid (3MP), a volatile compound from the endophytic bacterium Bacillus safensis, as a potent broad-spectrum antifungal agent. In vitro assays demonstrated 3MP’s efficacy against major pathogens (Magnaporthe oryzae Triticum, MoT, Fusarium graminearum, Bipolaris sorokiniana, Rhizoctonia solanacearum, Sclerotinia sclerotiorum), inhibiting mycelial growth and conidial germination by disrupting melanin synthesis and conidiogenesis. At 17.23 µM, 3MP completely suppressed MoT lesions and sporulation on detached wheat leaves. In vivo greenhouse trials confirmed dose-dependent protection against MoT (EC₅₀ = 4.3 µM), with full disease suppression at 17.23 µM. Soil fumigation with 3MP (10 µg/g soil) reduced viability of Fusarium oxysporum, Sclerotium rolfsii, and R. solanacearum by >90% in inoculated soils. Mechanistic studies revealed 3MP disrupts fungal membrane integrity, inducing cell death at micromolar concentrations. This study positions 3MP as a sustainable, dual-action novel biofumigant and biocontrol agent, offering a scalable solution to replace hazardous chemical fungicides such as methyl bromide in integrated disease management.