Detection Of Resistance To Five Kinds Of Fungicides And Development Of A Combined Mixture For Resistance Management In Botrytis Cinerea Causing Strawberry Grey Mould

The grey mould disease caused by Botrytis cinerea is the most important disease threatening the production of strawberries.This plant pathogenic fungus has very high risk of fungicide resistance development.Until present,management of grey mould disease highly depends on chemical control through applications of fungicides.Therefore,study of the fungicide resistance monitoring and management in B.cinerea has important practical significance.Benzimidazoles（such as carbendazim,diethofencarb）and dicarboximides（procymidon）are traditional fungicides for B.cinerea which are extensively used for many years.Fluazinam and fludioxonil are new type of fungicides with novel structures.This research aims to detect the resistance to these five fungicides in B.cinerea population collected from strawberry and develop a mixture based on pyraclostrobin and boscalid,two modern respiratory inhibitors,to provide information for fungicide resistance management in B.cinerea.The main results are as followings:（1）A total of 251 single-spored isolates were collected in 2018 from Liaoning,Hebei,Beijing,Xinjiang,Sichuan and Anhui province.Resistance to carbendazim（Car）,procymidon（Pro）and diethofencarb（Die）was detected by using the respective discriminate dosage of 5μg·m L^-1,1μg/·m L^-1and 5μg·m L^-1.Results showed that the resistance frequency in B.cinerea population（n=251）was67.33%,45.02%and 64.94%,respectively.There was significant difference in resistance frequency between provinces.Among them,for carbendazim,Beijing（96.55%）>Sichuan（75.00%）>Hebei（74.47%）>Liaoning（69.57%）>Anhui（59.26%）>Xinjiang（31.58%）;for procymidon:Anhui（55.56%）>Hebei（55.32%）>Sichuan（50.00%）=Beijing（50.00%）>Liaoning（34.78%）>Xinjiang（33.33%）;for diethofencarb:Xinjiang（77.19%）>Sichuan（75.00%）>Hebei（65.96%）>Liaoning（65.22%）>Anhui（55.56%）>Beijing（53.45%）;（2）Eight sensitive phenotypes were found in above B.cinerea population（n=251）:Car ^SPro ^SDie ^R（S=sensitive,R=resistant）,Car ^SPro ^RDie ^R,Car ^SPro ^SDie ^S,Car ^SPro ^RDie ^S,Car ^RPro ^SDie ^R,Car ^RPro ^SDie ^S,Car ^RPro ^RDie ^Rand Car ^RPro ^RDie ^R.Among them,only three isolates which were sensitive to all the three fungicides（Car ^SPro ^SDie ^S）were detected with the frequency of 1.2%while isolates which were resistant to all the three fungicides（Car ^RPro ^RDie ^R）were detected with the frequency of 17.53%.These results suggested that serious multi-resistance occurred in B.cinerea from strawberry.There was also significant difference in resistance phenotype between provinces.Xinjiang had all the eight phenotype and Anhui had the least phenotype,4.Car ^RPro ^RDie ^Rand Car ^RPro ^SDie ^Rwere observed in all the six provinces;（3）Resistance to fluazinam and fludioxonil in B.cinerea population（n=251）was detected by assessment the inhibitory percentage of fivefold concentration of sensitive baseline EC₅₀.Only one isolate,BD1 collected from Baoding city,Hebei province,resistant to fludioxonil was detected with the frequency of 0.4%.None fluazinam resistant isolate was found;（4）DCKX1,a isolate with triplicate-resistance（Car ^RPro ^RDie ^R）was adopted to develop a mixture based on pyraclostrobin and boscalid,two modern respiratory inhibitors.Results indicated that obvious synergistic action was found for the ratio of 4:1,3:1,2:1 and 1:1.When pyraclostrobin and boscalid was mixed at 2:1,the synergistic factor was as high as 3.64.This mixture provided satisfactory control efficacy against grey mould disease in plants.Our research suggested that it would be used on strawberry to delay and management resistance in B.cinerea.