Detection Of The Sensitivity Of Botrytis Cinerea To Six Succinate Dehydrogenase Inhibitors Fungicides And Study Of Resistance Mechanism To Boscalid In Shandong Province

In recent years,gray mold has became an important disease impacting crop production in protected areas of northern China,causing serious economic losses.At present,chemical control is the main method to control gray mold.Boscalid is a succinic dehydrogenase inhibitor fungicide,showed good control efficacy to Botrytis cinerea,and has became the main fungicide for B.cinerea controlling in Shandong Province.However,due to the single site of action and the increasingly prominent resistance of boscalid,it is necessary to monitor the sensitivity development of boscalid in Shandong continuously.It has been reported that the resistance of Botrytis cinerea to boscalid is because of mutation of subunits,but there were few reports had been published in China.Some SDHIs showed high efficiency against B.cinerea have been developed abroad,such as benzovindiflupyr,isopyrazam,pydiflumetofen,fluxapyroxad and fluopyram,which have not been registered in China for the control of B.cinerea until now.In this paper,spore germination method was used to determine the sensitivities of 103 B.cinerea isolates from different areas of Shandong Province to boscalid,benzovindiflupyr,isopyrazam,pydiflumetofen,fluxapyroxad and fluopyram.The mutant sites of B.cinerea resistant to boscalid were detected.In addition,this study analyzed whether there was cross-resistance between boscalid and benzovindiflupyr,isopyrazam,pydiflumetofen,fluxapyroxad,fluopyram,providing a basis for the registration and use of these fungicides.The relationship between cross resistance and resistance level was also analyzed.The main results are as follows:1.In 2018,the resistance frequency of B.cinerea to boscalid was relatively high in Shandong Province,among 103 tested strains tested,63 strains were resistant to boscalid,the total resistance frequency of B.cinerea to boscalid was 58.10%,and highly resistant isolates accounted for 17.14%;the proportion of moderately resistant strains and highly resistant strains increased year by year compared with 2016 years ago,The proportion of highly resistant strains increased from 2.63% in 2016 to 17.14% in 2018.2.Four mutant types of N230 I,H272Y,H272 R and P225 F were found in the resistant strains monitored in Shandong Province.Among them,two mutation types,N230 I and P225 F,have not been reported in China.H272 Y was the main mutant site of resistance to boscalid of B.cinerea in Shandong Province,accounting for 42.3% of all mutant strains,13 strains contained H272 R mutation,accounting for 11.54% of all mutant strains,9 strains contained N230 I mutation,accounting for 28.13% of all mutant strains,the proportion of P225 F mutant strains was 15.63%.No mutation of H272 L was detected.3.The sensitivity frequency of B.cinerea from Shandong province to benzovindiflupyr was 75.93%,and highly resistant isolates accounted for 3.70%.Sensitivity frequency to isopyrazam was 43.52%,and highly resistant isolates accounted for 10.19%.Sensitivity frequency to pydiflumetofen was 80.11%,and only one strain of high resistance,highly resistant isolates accounted for 0.93%.Sensitivity frequency to fluxapyroxad was 72.22%,highly and medium resistant isolates accounted for 11.11%.Sensitivity frequency to isopyrazam was 43.52%,and highly resistant isolates accounted for 10.19%.Sensitivity frequency to fluopyramwas 41.67%,and lowly resistant isolates accounted for 47.22%,highly resistant isolates accounted for 3.70%.4.In addition,interactive resistance existed between boscalid and other fungicides,such as benzovindiflupyr,isopyrazam,pydiflumetofen,fluxapyroxad,fluopyram and the correlation was significant.5.The sensitivity of different mutation types to different fungicids was different.Among the four mutant types of resistant strains,P225 F was resistant to all SDHIs fungicides tested,and showed high resistance to most SDHIs fungicides.H272 R showed low resistance to most of the tested fungicides,moderate resistance to boscalid and sensitivity to fluxapyroxad;H272Y also showed low resistance to most fungicides,high resistance to boscalid and moderate resistance to isopyrazam;N230I was sensitive to pydiflumetofen and showed varying degrees of resistance to other fungicides.