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Multiple Resistance of Botrytis cinerea from Vegetable Crops to Carbendazim, Diethofencarb, Procymidone, and Pyrimethanil in China

One hundred and eight isolates of Botrytis cinerea from greenhouse cucumber and tomato in two locations in Jiangsu Province (Nanjing and Huaiyin) and one location in Shandong Province were tested for their sensitivities to the four fungicides commonly used in China. Isolates with resistance to all four fungicides—carbendazim, diethofencarb, procymidone, and pyrimethanil (Car^RDie^RPrc^RPyr^R)—were found in all three regions in this study. High frequencies (52 and 53%) of resistance to all four fungicides were observed among the 62 isolates collected in Nanjing and the 36 isolates collected in Huaiyin in Jiangsu Province. The 10 isolates from Shandong Province were all resistant to the four fungicides. Pathogenicity and sporulation in vivo, and mycelial growth, sporulation, spore germination, and osmotic sensitivity to NaCl in vitro, were similar for the group of quadruple-resistant and wild-type isolates (P > 0.05). In the present study, the complete two-component histidine kinase gene (Bos1) was sequenced for 10 procymidone-resistant and 3 procymidone-sensitive B. cinerea isolates. Isolates representing four different procymidone-resistant phenotypes (Car^RDie^SPrc^RPyr^S, Car^RDie^RPrc^RPyr^S, Car^RDie^RPrc^RPyr^R, and Car^RDie^RPrc^RPyr^R) all had nucleic acid point mutations resulting in amino acid changes at position 369 (change from glutamine to proline) as well as at amino acid position 373 (asparagine to serine) in the Bos1 gene.