Purpureocillium lilacinum as a bio-nematicide: Mechanistic insights into cuticle penetration and acetoin toxicity against Bursaphelenchus xylophilus

Bursaphelenchus xylophilus , a destructive nematode in pine forestry, poses significant challenges for control through sustainable chemical methods. This study introduces Purpureocillium lilacinum as an eco-friendly biocontrol alternative, exploring its nematicidal mechanism. In coculture with B. xylophilus , the fungus caused cuticle rupture and nematode death. Microscopic examination revealed fungal spores attaching to, germinating on, and penetrating the nematode cuticle via mechanical pressure and extracellular enzymes, ultimately resulting in host lysis through toxin secretion with dichloromethane and ethyl acetate demonstrated- and time-dependent nematicidal activity, with the ethyl acetate extract acting more swiftly within 12 h. By 72 h, the 15 % ethyl acetate extract achieved a 99 % mortality. Transcriptomic analysis showed that enhanced pyruvate metabolism supported fungal energy supply and secondary metabolite synthesis, while acetoin and lactate branches provided complementary metabolic overflow strategies to maintain redox balance. Furthermore, bioassays confirmed, for the first time, the direct nematicidal activity of the volatile metabolite acetoin, with an LC₅₀ of 9.62 mg/mL. At 36 h, the nematicidal rate of 13 mg/mL acetoin reached a peak value of 96 %. These findings reveal that P. lilacinum operates through multienzyme synergy, secondary metabolites, and efficient pyruvate metabolism. This study systematically elucidates the fungal pathogenesis mechanism, offering crucial targets and a theoretical foundation for developing green control strategies against pine wilt disease and novel biopesticides. • Purpureocillium lilacinum ruptures the cuticle of Bursaphelenchus xylophilus. • Pyruvate metabolism supports fungal nematicidal. • Acetoin and lactate branches work together as metabolic overflow strategies to redox balance. • The volatile metabolite acetoin shows nematicidal activity LC₅₀= 9.62 mg/mL.