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Fusarium head blight (FHB) is caused by Fusarium graminearum, which contributes serious economic losses to crop yields, and is an epidemic disease of wheat. The resistance to tebuconazole of 1,118 F. graminearum strains obtained from different areas of Henan Province in 2018–2020 was determined by the discriminatory doses of 5.0 μg/ml. A total of 362 F. graminearum strains resistant to tebuconazole were detected, and the frequency of resistance of F. graminearum strains to tebuconazole was 30.7%. The EC50 and EC90 values of F. graminearum strains to tebuconazole were calculated according to the mycelial growth inhibition of the Henan F. graminearum population. The range of EC50 values of 756 sensitive strains and 362 resistant strains were 0.01–0.69 and 0.02–3.31 μg/ml, and the average ± SD EC50 of sensitive and resistant strains were 0.13 ± 0.01 and 0.40 ± 0.13 μg/ml. The range of EC90 values of 756 sensitive strains and 362 resistant strains were 0.31–4.89 and 0.65–18.69 μg/ml, and the average ± SD EC90 values were 1.13 ± 0.05 and 2.98 ± 0.09 μg/ml. The CYP51A and CYP51B genes of the sensitive and resistant strains were amplified separately by polymerase chain reaction (PCR) and analysed. The results showed that among the 150 resistant strains, only six resistant strains had amino acid mutation, which changed from serine to tyrosine (TCA‐TAT, Ser‐Tyr) at position 169 of CYP51B gene, and no amino acid mutation was found in CYP51B of the other 144 resistant strains. No amino acid mutation was found in the CYP51A gene of 150 resistant strains. These results provide important information to growers for monitoring tebuconazole resistance in F. graminearum field populations from wheat in Henan Province. [ABSTRACT FROM AUTHOR]

Abstract: Sclerotinia stem rot caused by Sclerotinia sclerotiorum is one of the most important diseases in oilseed rape‐growing areas of China. To determine the frequency of resistance of field isolates of S. sclerotiorum to carbendazim and dimethachlone, a total of 556 isolates from 10 different regions of Henan Province were obtained between 2015 and 2016. The frequency of isolates with a high‐resistance phenotype and a moderate‐resistance phenotype to carbendazim was 69.2% and 10.8%, respectively. However, S. sclerotiorum isolates resistant to dimethachlone were not detected. The baseline sensitivity of S. sclerotiorum to dimethachlone was distributed as a unimodal curve with a mean EC50 value of 0.39 ± 0.09 μg ml−1 for the inhibition of mycelial growth. Four dimethachlone‐resistant mutants were obtained from 20 wild‐type isolates induced by exposure to increasing concentrations of the fungicide in vitro. The mutants showed high levels of resistance to dimethachlone, with resistance factors that ranged from 179 to 323. Positive cross‐resistance occurred between dimethachlone and procymidone, iprodione, and fludioxonil; however, no cross‐resistance was observed for carbendazim and boscalid. The fitness of the dimethachlone‐resistant mutants was significantly lower than that of the wild‐type isolates, as measured by mycelial growth, hyphal dry weight, sclerotium number and dry weight, and pathogenicity. Additionally, based on osmotic tests, the inhibition of mycelial growth caused by NaCl applied at different concentrations was significantly higher for the dimethachlone‐resistant mutants than for their wild‐type parents. [ABSTRACT FROM AUTHOR]