The FgSdhAF2–FgSdhA Interface as a Potential Novel Antifungal Target in Fusarium graminearum : Genetic Characterization and Structure-Based Inhibitor Discovery

Fusarium graminearum causes Fusarium head blight and threatens cereal production through deoxynivalenol (DON) contamination. The biological role of FgSdhAF2 was characterized, and a potential antifungal pocket adjacent to the FgSdhAF2–FgSdhA interface was identified. Deletion of FgSdhAF2 markedly reduced mycelial growth, conidiation, virulence, DON production, and FgTri5 expression in SDHI-sensitive PH-1 and intrinsically resistant G1. The FgSdhAF2 E159Y substitution similarly reduced mycelial growth, conidiation, and virulence. Using this predicted pocket for structure-based virtual screening, approximately 1.6 million compounds were screened, yielding ten candidates. Compound 156758 inhibited PH-1, G1, and the highly pydiflumetofen-resistant FgSdhC1A83 V mutant, with EC50 values of 3.33–3.59 μg/mL, and reduced DON accumulation by 53.9–55.4%. It also showed broad-spectrum activity against eight additional phytopathogenic fungi. Collectively, these findings support this predicted interface as a potential antifungal target and 156758 as a lead compound for developing fungicides to manage SDHI-resistant F. graminearum populations.