| Botrytis cinerea has a high risk of developing resistance to fungicides.It destroys more than 200 plant species,including vegetables,fruit trees and flowers.Owing to production of numerous spores,four active transposons,rapid evolution of genome and broad host spectrum,this pathogen ranks the secondary among the "top-ten" severest pathogens worldwide.To update,no resistant varieties against grey mold are available.Therefore,chemical control is relied.Because the minor environment provided by the commercial strawberry greenhouses is beneficial for the occurrence and prevalence of this disease,B.cinerea easily develops multiple resistances against the fungicides with different modes of action,including carbendazim,diethofencarb,pyrimethanil,procymidone and boscalid after several years of their usage.Fludioxonil,belonging to phenylpyrroles,has been used to control grey mold in the foreign countries for more than three decades.In China,however,the fungicide was first registered in 2012 for the prevention and control of the disease on flowers.Owing to the prevalence of multiple resistance against fungicides,strawberry farmers usually fail to find an effective fungicide to control it.It was informed that fludioxonil was used to control gray mold in commercial strawberry greenhouses from Zhenjiang,Jiangsu in 2013.The current study is conducted in order to determine whether the fludioxonil-resistant populations develop in the greenhouses after three years of the first application.During previous study of our laboratory,2 highly fludioxonil-resistant isolates have been obtained from commercial cucumber greenhouses in Shouguang,Shandong province.The similarity and difference in biological characteristics were compared between highly fludioxonil-resistant isolates from Shouguang-originated cucumber and Zhenjiang-originated strawberry greenhouses in the current study.The results in detail were followed.(1)184 isolates separated from diseased fruits were detected by the method of discriminable dosage.The frequency of low-resistant strains was 2.72%,and the frequency of highly-resistant strains was 0.58 isolates were separated from diseased flower stems.The frequency of low-resistant strains was 13.79%,and the frequency of high resistant strains was 5.17%.In Shouguang city,Shandong province of China,fludioxonil is sprayed twice to control grey mold in a growth cycle of cucumber planted in the commercial greenhouse,whose selection pressure of fludioxonil for B.cinerea is much lower than that in one growth cycle of strawberry in the commercial greenhouse of Zhenjiang city,Jiangsu province with at least four sprayings of fludioxonil for three years.(2)The hyphae growth rate,pathogenicity,sporulation,sclerotia capacity and tolerance of osmotic agents were significantly lower than those of sensitive strains.It showed positive interaction resistance with dicarboximide fungicides.Compared with the resistant strains of cucumber from Shouguang greenhouses in Shandong province,the production and formation of sclerotia were significantly increased.(3)After the comparison analysis of the whole sequence of the Botrytis cinerea two-component histidine kinase gene(BcOS-1),we found that high resistant isolates from facilities on the strawberry has two genotypes,(F127S+I365N+S426P)and(G538R+A1259T),respectively,which were totally different from highly-resistant strains from Shandong Shouguang greenhouses on cucumber.(4)The molecular docking results of the encoding protein from five strains of highly-resistant strain BcOS-1 showed that all proteins encoded by BcOS-1 from the highly-resistant strains had less affinity than the sensitive strains. |
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