Isolation, Identification, and Antimicrobial Activity of Secondary Metabolites from Pseudophaeolus soloniensis Against Phytopathogenic Fungi

Plant pathogenic fungi pose a major threat to global crop production and food security, necessitating the development of sustainable control agents. This study investigated the antifungal potential of Pseudophaeolus soloniensis, a wood-decaying fungus. A wild strain was isolated from Hebei, China, and identified via morphology and ITS sequencing. A bioactive crude extract (P1) was obtained through optimized solid-state fermentation on A3M medium. Its antimicrobial spectrum was evaluated against major phytopathogenic fungi (e.g., Fusarium graminearum, Aspergillus flavus) and model bacteria (Staphylococcus aureus, Escherichia coli) using mycelial growth inhibition, Minimum Inhibitory Concentration (MIC), and agar diffusion assays. P1 exhibited strong, selective activity, showing significantly greater inhibition against S. aureus than E. coli and pronounced effects against F. graminearum (43.79% inhibition at 20 µg/mL) and A. flavus (73.5% at 0.2 mg/mL). A hormetic-like response was observed for F. oxysporum. Liquid Chromatography-Mass Spectrometry (LC-MS) analysis revealed a diverse secondary metabolome, including flavonoids, alkaloids, quinones, and saponins. These results establish P. soloniensis as a promising source of bioactive metabolites for developing eco-friendly fungicides.