Study On The Resistance To Dicarboximide And Benzamide Fungicides In Botrytis Cinerea From Tomato And Strawberry In Hubei Province,China

Gray mold disease caused by Botrytis cinerea causes severe problems around the world.B.cinerea is the pathogen of more than 200 host plants including tomato and strawberry.In this study,B.cinerea from tomato and strawberry was used to explore the status of resistance development to two fungicides of dicarboximide and benzamide.The sensitivity of B.cinerea isolates from various tomato and strawberry growing locations of Hubei province was determined to different fungicides.Molecular detection and characterization of resistance were investigated along with fitness studies.This study documents the detection of various point mutations along with the discovery of a new mutation.Briefly,the results are as follows:1)Strawberry and tomato are important crops grown commercially all over the world.China,an important grower of strawberry and the largest producer of tomato is greatly affected by gray mold disease caused by B.cinerea.In this study,B.cinerea isolates collected from tomato and strawberry greenhouses at different locations in Hubei province were evaluated for their sensitivity to fungicide procymidone.The mean EC50 values(effective concentration to cause 50% growth inhibition)of procymidone for sensitive and resistant isolates were 0.25 ?g/ml and 3.02 ?g/ml,respectively.The frequency of resistant(ProR)isolates was 16%,and the highest frequency was recorded in Jingmen.Positive cross-resistance was observed for ProR isolates to other dicarboximide fungicides,but not to phenylpyroles.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 Bc Os1 gene revealed that procymidone resistant isolates either carried point mutations at codon 365(I365S)or a pair of point mutations at codons 369(Q369P)and 373(N373S).Results of this study will be useful to design effective strategies for the management of fungicide resistance.2)B.cinerea isolates collected from tomato and strawberry greenhouses at different locations in Hubei province were also screened for resistance to a benzamide fungicide,zoxamide.In mycelial growth assays,the mean EC50 values for zoxamide sensitive(Zoxs)and resistant(ZoxR)isolates were 0.27 ?g/ml and 4.98 ?g/ml,respectively.About 8.5% isolates from eight locations were found to be resistant to zoxamide.However,among the locations tested,the highest frequency of resistance was recorded in Jingmen(53%).There was positive-cross resistance detected for ZoxR isolates to carbendazim.No significant differences were observed for fitness parameters between Zoxs and ZoxR isolates,indicating high resistance risk.Sequence analysis of the TUB2 gene of B.cinerea revealed three previously reported point mutations(E198A,E198 K,F200Y)and one new point mutation T351 I.This new mutation appeared only in those isolates which possessed E198 K point mutation but not with E198 A.Another mutation F200 Y was detected in high resistant isolate.The discovery of the new point mutation T351 I and all other mutations indicates the rising threat of resistance development.This study demonstrates a better understanding of the resistance development profile in Hubei province,China.Results will be beneficial for the improvement of fungicide resistance management strategies.