Discovery of WML-01, a Spirocyclic Butenolide Derivative Featuring a Rhodanine Motif, Exhibiting High Fungicidal Activity against Fusarium Species

Controlling the Fusarium head blight (FHB) epidemic and deoxynivalenol (DON) contamination, predominantly caused by Fusarium graminearum, remains challenging. In this study, rhodanine was introduced into a spirocyclic butenolide-based chemical library to design novel fungicidal agents. In vitro assays revealed that target compounds exhibited excellent activities against F. graminearum, F. fujikuroi, and Sclerotinia sclerotiorum. The EC₅₀ of the representative compound WML-01 was 0.079 μg/mL against F. graminearum and 0.72 μg/mL against F. fujikuroi. Transmission electron microscopy showed that WML-01, like phenamacril, disrupted the cell membrane of F. graminearum, causing deposition of lipid droplets. WML-01 inhibited DON biosynthesis as effectively as phenamacril but showed no cross-resistance, indicating a different mode of action. Transcriptome analysis indicated that WML-01 strongly suppresses ribosomal subunit assembly, impairing protein synthesis. Field trials demonstrated that WML-01 performs comparably to phenamacril in controlling FHB. Overall, WML-01 is a promising candidate for managing FHB and DON contamination.