Biological characterization of Botrytis cinerea isolates with different sensitivity types to pydiflumetofen

To determine the biological characteristics of Botrytis cinerea with different sensitivity types to pydiflumetofen, the resistance stability of nine B. cinerea isolates with different sensitivity types to pydiflumetofen was determined by the mycelial growth method, after sub-cultivation on fungicide-free PDA plates for ten generations, the biological characteristics such as mycelial growth rate, conidial production, conidium germination rate, and pathogenicity of these nine isolates were determined on PDA medium and detached leaves; The sensitivity of these nine isolates to temperature, pH value, and glucose was determined by mycelial growth method, and the four succinate dehydrogenase subunits gene A(SdhA), B(SdhB), C(SdhC) and D(SdhD) were cloned and sequenced. These results showed that the factors of sensitivity change (FSC) of two low-resistant isolates, two medium-resistant isolates, and two high-resistant isolates obtained from the field ranged from 0.60 to 1.15, while the FSC of the high-resistant isolate BLH5F obtained by fungicide-selection in the laboratory was 0.23. There was no significant difference between resistant and sensitive phenotypes of the B. cinerea isolates on mycelial growth, spore production, conidium germination rate, and pathogenicity, except that the mycelial growth rate of the low-resistant isolate WP8 was significantly lower than that of the two sensitive isolates, and the spore productions of the medium-resistant isolate WP6 and the high-resistant isolate WPE9 were significantly lower than that of the two sensitive isolates. On the whole, there was no significant difference between the seven resistant isolates and the two sensitive isolates in the sensitivity to temperature, pH value, and glucose. The histidine (His) was replaced by arginine (Arg) at position 272 of SdhB gene (H272R) in the high resistance isolate BLH5F obtained from the laboratory by fungicide-selection and the proline (Pro) changed to leucine (Leu) at position 225 of SdhB gene (P225L) in two low-resistant isolates, two medium-resistant isolates, and two high-resistant isolates obtained from the field. All the results showed that the fitness of B. cinerea with different sensitivity types to pydiflumetofen was similar. So, it was speculated that the isolates resistant to pydiflumetofen were easy to form a dominant population under the fungicide selection in the field.