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Altogether, 192 Botrytis cinerea isolates collected from tomato greenhouses at different locations in Hubei Province were evaluated for their sensitivity to fungicides procymidone and zoxamide. The mean effective concentration to cause 50% growth inhibition (EC 50 ) values of procymidone for sensitive and resistant isolates were 0.25 and 3.60 μg/ml, respectively. The frequency of procymidone-resistant (Pro R ) isolates was 18%, and the highest frequency was recorded in Jingmen. Positive cross-resistance was observed for Pro R isolates to other dicarboximide fungicides but not to phenylpyrroles. Significant differences were observed for fitness parameters (i.e., mycelial growth, osmotic sensitivity, and virulence between sensitive and resistant isolates). Amino acid sequence of the Bos1 gene revealed that Pro R isolates carried either point mutations at codon 365 (I365S) or a pair of point mutations at codons 369 (Q369P) and 373 (N373S). For zoxamide, the mean EC 50 values for sensitive and resistant isolates were 0.22 and 5.32 μg/ml, respectively. Approximately 14% of the isolates were found to be resistant to zoxamide, and the highest frequency of resistance was also observed in Jingmen. There was positive cross-resistance for zoxamide-resistant (Zox R ) isolates to carbendazim. No significant differences were observed for fitness parameters between zoxamide-sensitive and Zox R isolates. Sequence analysis of the β-tubulin gene of Botrytis cinerea revealed two previously reported point mutations (E198A and E198K) and one new point mutation (T351I). This new mutation was detected in only those isolates which possessed the E198K but not E198A substitution. This study allows for a better understanding of the resistance development profile in Hubei Province. Results will be useful for the improvement of fungicide resistance management strategies.

Two hundred and forty isolates of Botrytis cinerea were collected during the early summer of 2012 and 2013 from strawberry greenhouses in 10 locations in Hubei Province and examined for sensitivity to five fungicides, most of which were commonly used to control this fungus. High frequency of resistance to carbendazim (Car, 63.63%) and cyprodinil (Cyp, 42.42%) was detected. Boscalid-resistant (Bos R ) isolates were detected for the first time in China, whereas no fludioxonil-resistant isolates were identified. Dual resistance to carbendazim and diethofencarb (Die) was also detected. There were six phenotypes of resistance profile (i.e., Car R Die S Bos S Cyp S , Car R Die R Bos S Cyp S , Car R Die S Bos S Cyp R , Car R Die S Bos R Cyp S , Car R Die R Bos S Cyp R , and Car R Die S Bos R Cyp R ). Car R Die S Bos S Cyp S and Car R Die S Bos S Cyp R were the most common phenotypes, occurring at eight and seven locations, respectively. After 10 successive transfers on fungicide-free potato dextrose agar, tested resistant isolates retained levels of resistance similar to or comparative with the initial generation, indicating the stability of these resistances. Fitness evaluations based on investigation of mycelial growth, osmotic sensitivity, sporulation in vitro and in vivo, and virulence revealed the uncompromising fitness in resistant isolates, except that decreased virulence was observed in Bos R isolates. The molecular basis of carbendazim, diethofencarb, and boscalid resistance was investigated. Results showed that all 13 sequenced carbendazim-resistant isolates harbored the mutation E198V or E198A in the β-tubulin gene and the five isolates with dual resistance to carbendazim and diethofencarb showed the mutation E198K in the same gene. Bos R isolates possessed the H272R mutation in succinate dehydrogenase subunit B gene. The results achieved in this study challenge the current management strategies for B. cinerea, which largely depend on applications of these fungicides.