Multiple-fungicide resistance to carbendazim, diethofencarb, procymidone, and pyrimethanil in field isolates of Botrytis cinerea from tomato in Henan Province, China

Botrytis cinerea, the fungal pathogen responsible for causing gray mold in tomatoes, frequently exhibits multiple fungicide resistance. In this study, the sensitivity to carbendazim (Car), diethofencarb (Die), procymidone (Prc), and pyrimethanil (Pyr) was determined for 263 isolates of B. cinerea from diseased fruit and leaves of tomato plants from 87 commercial greenhouses in Henan Province of China during 2013 and 2014. Of the isolates tested, 89%, 93%, 85%, and 86% were resistant to Car, Die, Prc, and Pyr, respectively. Twelve phenotypes were found having different sensitivity patterns, and multi-fungicide resistance was found to one, two, three or four fungicides. The percentage of multiple fungicide resistant isolates (CarRDieRPrcRPyrR) was 68%. Mycelial growth, spore production, and mycelial dry weight were not significantly different between resistant and sensitive phenotypes of the B. cinerea isolates. However, the virulence of CarSDieRPrcSPyrS isolates was higher than that of the other fungicide-resistance phenotypes. All of the carbendazim and diethofencarb resistant phenotypes carried a point mutation at codon 198 (E198A or E198K) or 200 (F200Y) in the β-tubulin gene, and all of the procymidone resistant phenotypes carried point mutations at codons 369 (Q369P) and 373 (N373S) in the Bos1 gene. These results provided important reference data for assessment of resistance risk of B. cinerea isolates from commercial tomato transplants in Henan Province, indicating the existence of a high frequency of resistance to carbendazim, diethofencarb, procymidone, and pyrimethanil revealing the necessity of a more integrated control of gray mold.