Fusarium head blight, also called scab, is caused by Fusarium graminearum and is one of the most important destructive diseases of wheat. The frequency of carbendazim resistance in 1,132 isolates of F. graminearum recovered from fields in different regions of Henan Province in 2016, 2017, and 2018 was determined. A total of 31 F. graminearum isolates resistant to carbendazim were detected, including 30 moderately resistant isolates and one highly resistant isolate. The frequency of resistance of F. graminearum isolates to carbendazim was 2.7%. The range of effective concentration (EC50) values of 1,101 sensitive isolates and 30 moderately resistant isolates was 0.08 to 0.98 μg ml-1 and 2.73 to 13.28 μg ml-1, respectively. The mean ± SD EC50 value was 0.55 ± 0.13 μg ml-1 and 5.61 ± 2.58 μg ml-1, respectively. The EC50 value of the highly resistant isolate was 21.12 μg ml-1. Point mutation types of the carbendazim-resistant isolates were characterized by cloning the β2-tubulin gene of 31 resistant isolates. Three point mutation types at amino acids F167Y, E198Q, and E198L in the β2-tubulin gene of resistant isolates were identified. Among 31 resistant isolates, the frequency of point mutation types in F167Y, E198Q, and E198L of the β2-tubulin gene was 71.0, 25.8, and 3.2%, respectively. The data indicate that F. graminearum has developed resistance to carbendazim in Henan Province, and single point mutations at amino acid F167Y were the predominant type of mutation detected.
Keywords: benzimidazole; fungicide.