Sensitivity baseline and resistance risk assessment of Coniella vitis , the pathogen of grape white rot, to the novel fungicide Mefentrifluconazole

Grape white rot threatens grape production worldwide. To evaluate the resistance and risk of Coniella vitis causing grape white rot in Shandong province to mefentrifluconazole, the sensitivity baseline of C. vitis to mefentrifluconazole was established, and the pathogen's resistance risk was evaluated. Field trials revealed that mefentrifluconazole is one effective fungicide for controlling grape white rot, with the control effect of over 92% at a concentration of 133.33 mg/kg. The EC50 values of 85 strains of C. vitis to mefentrifluconazole ranged from 0.021–10.031 μg/mL, exhibiting a multimodal distribution in their EC50 frequency. However, the EC50 frequency distribution of 71 strains followed a normal distribution within the first peak, with an average EC50 of (0.757 ± 0.412) μg/mL, which could be used as the sensitivity baseline for C. vitis in Shandong province. Resistant strains showed no decline in growth rate, spore production, or pathogenicity. In act, some resistant strains even exhibited superior characteristics. Cross-resistance analysis showed significant correlations between mefentrifluconazole and difenoconazole (r = 0.819) and propiconazole (r = 0.604), but no significant cross-resistance with pyraclostrobin, thiram, mancozeb, carbendazim, imazalil, or tebuconazole. This study provides a theoretical basis for fungicide management of grape white rot.