Baseline sensitivity of Fusarium graminearum from wheat fields in Henan,China, to metconazole and analysis of cross resistance with carbendazim and phenamacril

The filamentous plant pathogenic fungus Fusarium graminearum is one of the most important pathogens causing Fusarium head blight (FHB) in wheat in the Henan Province of China. Metconazole is among the demethylation inhibitor (DMI) fungicides with a higher inhibitory activity on the mycelial growth of F. graminearum. In 2016 and 2017, 119 single spore isolates of F. graminearum, prior to being exposed to metconazole, were recovered from 52 wheat fields near 11 cities in Henan Province. The inhibitory activity of metconazole on the mycelia of the Henan F. graminearum population was determined, and EC₅₀ values were calculated. The range of EC₅₀ values of the Henan F. graminearum population to metconazole was 0.0103 to 0.0775 μg/ml with an average EC₅₀ value of 0.0293 ± 0.0114 μg/ml. The sensitivity frequency distribution curve presented a single peak in a narrow range. No cross-resistance was found between the DMI fungicide metconazole and the benzimidazole fungicide carbendazim or the cyanoacrylate fungicide phenamacril. Therefore, these sensitivity data could be used as the baseline of F. graminearum susceptibility to metconazole in the Henan Province and provide the basis for monitoring metconazole resistance in this area.