Characterization of the resistance mechanism and risk of Fusarium verticillioides to the myosin inhibitor phenamacril

Fusarium verticillioides is a major pathogen of maize that causes ear rot and produces mycotoxins. Phenamacril is a novel cyanoacrylate fungicide that exhibits favorable activity against Fusarium species. In this study, the phenamacril-resistant mutants of F. verticillioides were obtained by ultraviolet mutagenesis. Single point mutations of S73L or E276K in the myosin-1 FvMyo1 were proven to be responsible for the high-level resistance of F. verticillioides to phenamacril. Phenamacril had a significant impact on the localization of the wild-type FvMyo1 (FvMyo1(WT)-green fluorescent protein [GFP]), but not on the mutated FvMyo1 (FvMyo1(S73L)-GFP and FvMyo1(E276K)-GFP) at the hyphal tips. Molecular docking analysis suggested that mutation (S73L or E276K) in FvMyo1 altered the binding mode and decreased the binding affinity between phenamacril and myosin-1. There was no significant fitness penalty in mycelial growth, conidiation, and virulence of F. verticillioides associated with resistance to phenamacril. The results will enhance our understanding of the resistance mechanism of F. verticillioides to phenamacril and provide new reference data for the management of maize ear rot.