Sensitivity and Resistance Risk Assessment of from Wheat to Prothioconazole.

Fusarium head blight (FHB), caused mainly by , is one of the most devastating diseases of wheat. Prothioconazole is a broad-spectrum demethylation inhibitor fungicide with excellent efficacy against FHB. In this study, 235 strains of collected from different regions of Henan Province of China in 2016, 2017, and 2018 were randomly selected. The sensitivity of to prothioconazole was determined by the mycelial growth inhibition method. The results showed that the half maximal effective concentration (EC) values of to prothioconazole ranged from 0.4742 to 3.4403 μg/ml, and the average EC value was 1.7758 ± 0.6667 μg/ml. The sensitivity frequency distribution presented a consequent unimodal curve, and thus the average EC value can be established as the baseline sensitivity of to prothioconazole. Ten strains of prothioconazole-resistant mutants were obtained by fungicide taming, and the resistance factor of the mutants ranged from 5.71 to 12.32. The genetic stability assay showed that resistance can be inherited stably for 10 generations. All mutants displayed different degrees of defects in vegetative growth, conidia formation, and pathogenicity compared with the parental strain. These results indicated that has a low risk of resistance to prothioconazole. Cross-resistance assay showed that no cross-resistance was found between prothioconazole and carbendazim, tebuconazole, phenamacril, and pydiflumetofen. Among all mutants, sequence analysis showed that no mutation site was found in and . Real-time PCR assays showed that the expression levels of and of the mutants were significantly increased after prothioconazole treatment for 24 h. In summary, our study provided a theoretical basis for the resistance risk assessment of to prothioconazole and scientific application of prothioconazole in controlling FHB.