Sensitivity of Japanese Fusarium graminearum species complex isolates to metconazole

The sensitivity of the Fusarium graminearum species complex, the causal fungus of Fusarium head blight, to metconazole was measured. The minimum inhibitory concentrations (MIC) of 101 isolates ranged from 0.20 to 6.25 mg/l with a single peak at 1.56 mg/l. The effective concentration for 50% growth inhibition (EC(50)) was <0.1 mg/l in about 80% of isolates, and no isolate was significantly less sensitive to metconazole among this group. Among the E graminearum species complex, E asiaticum and F graminearum s. str. were identified by PCR-RFLP. The trichothecene chemotypes were determined as 3ADON, 15ADON, or NIV by multiplex PCR. Although species-specific geographical distributions and mycotoxin production characteristics were found, the MIC values to metconazole of both species were distributed within a similar range, and no significant difference in sensitivity was observed between the species or trichothecene chemotypes. Next, CYP51 genes from isolates with different sensitivities to metconazole were amplified by PCR, and their sequences were compared. As a result, it was suggested that the differences in sensitivity to metconazole between the isolates were not due to the substitution of amino acids in CYP51, the target enzyme of DMI. Then, macrospores from isolates with various sensitivities to metconazole were sprayed onto wheat ears, and the efficacy of metconazole was examined. Metconazole showed high control activity against every isolate. (C) Pesticide Science Society of Japan