Novel Fungicide 4-Chlorocinnamaldehyde Thiosemicarbazide (PMDD) Inhibits Laccase and Controls the Causal Agent of Take-All Disease in Wheat, Gaeumannomyces graminis var. tritici

Our aim was to investigate the bioactivity and mode of action of a novel fungicide 4-chlorocinnamaldehyde thiosemicarbazide (PMDD). As a result of its efficacy against various plant pathogens, its protective fungicidal activity, and systemic transport after root treatment, PMDD could be a promising fungicide to control wheat root diseases. In a field assay, PMDD showed good control efficacy on wheat take-all disease. A biochemical study indicated that PMDD acts as a laccase inhibitor, a to date unique mode of fungicidal action. Moreover, a total of seven stable PMDD-resistant Gaeumannomyces graminis var. tritici (Ggt) mutants were generated and demonstrated no cross-resistance with any commercial fungicides used for take-all disease control, and the gene expression profile further confirmed that laccase could be the target of PMDD. Taken together, we conclude that PMDD is a laccase inhibitor and could be used on wheat to control take-all diseases. The current study could strongly benefit the registration and application of PMDD.