Fungal colonization and candidate metabolite-mediated toxicity of Fusarium solani KMZW-1 against adult Bactrocera dorsalis.

This study examined the interaction between Fusarium solani KMZW-1 and adult Bactrocera dorsalis, with emphasis on cuticular colonization, adult-stage pathological effects, and candidate metabolite-mediated toxicity. KMZW-1 showed Fusarium-like colony and conidial morphology and colonized mainly tarsal setae, joints, and recessed cuticular regions, where fungal conidia and hyphae progressively accumulated over time. Fungal treatment reduced adult survival in a concentration-dependent manner (P < 0.001) and lowered egg production per female, likely due to reduced male survival and fewer mating opportunities, whereas egg hatchability, larval pupation, and adult emergence of offspring were not significantly affected (P > 0.05). Untargeted LC-MS/MS profiling annotated 3073 metabolites, and candidate secondary metabolites were prioritized using pathway assignment, CAS-confirmed identity, normalized peak-area abundance, reported biological activity and commercial availability. Among coumarin, umbelliferone and podophyllotoxin, podophyllotoxin showed the lowest 24 h LC50 values against adult flies, at 24.33 μg mL-1 for females and 21.03 μg mL-1 for males. These results indicate that KMZW-1 produces a reproducible surface-colonization-associated adult-stage phenotype in B. dorsalis. Podophyllotoxin should be interpreted as a prioritized candidate with confirmed topical toxicity, not as a confirmed in vivo virulence determinant. Further work is required to confirm metabolite identity with authentic standards, quantify metabolite production during infection, determine internal invasion dynamics, and evaluate mode of action and non-target safety.