| Peach bacterial shot hole caused by Xanthomonas arboricola pv.pruni(Xap)is an important disease of peach trees,which seriously affects the production of peach.Harpin protein produced by plant pathogenic bacteria has the function of exciton,which can induce hypersensitive response(HR)on non-host plants such as tobacco,and also has the function of pathogenic factor.So far,there hasn’t any report about harpin protein of Xanthomonas arboricola pv.pruni(Xap).Therefore,the occurrence dynamics and prevention and control of peach bacterial perforation were studied in the field.Meanwhile,the harpin coding gene of Xap was cloned and expressed in this paper,which laid a theoretical foundation and basis for the control of this disease.A continuous and dynamic investigation of peach bacterial perforation was carried out at peach garden in yangshan,Wuxi,Jiangsu province in 2018 and 2019,and it was found that the bacterial perforation occurred in late April and early May,and the disease expanded rapidly from June to August.Disease investigation data and weather conditions at that time were analyzed,and found that the occurrence of peach bacterial disease was related to both rainfall and temperature,larger rainfall or continuous rainfall days and higher average daily temperature were the necessary condition of the disease occurrence,the morbidity was closely related to the rainfall,especially.The greater rainfall and the longer the duration,the faster the disease will rise.In addition,field drug control studies were conducted in yangshan city of Wuxi and Yizheng of Yangzhou,Jiangsu province,in 2018 and 2019.The results showed that in peach garden of Wuxi in 2018,tetramycin and zineb had better prevention and control effects,followed by streptomycin sulfate for agricultural use,zinc thiazole,bromothalonil and kasugamycin copper oxychloride,while benziothiazolinone and zhongshengmycin·copper acetate had worse prevention and control effects.In Yizheng peach garden of Yangzhou in 2018,tetramycin,mancozeb and zinc thiazole showed better prevention effect,followed by streptomycin sulfate for agricultural use,zineb and bromothalonil,while kasugamycin·copper oxychloride and zhongshengmycin·copper acetate showed drug damage.In peach garden of Yangzhou in 2019,N.N-dioctyldivinyltriamine acetate and the combination of agents performed better in prevention effect,followed by chloro-bromo-isocyanuric acid,tetramycin,zhongshengmycin and mancozeb,while bordeaux mixture had a worse effect.Therefore,tetramycin had a better effect in preventing and treating peach bacterial shot hole in peach gardens of the two placesIn this work,gene sequence of xopA from Xanthomonas arboricola was found by NCBI database.Primers were designed based on xopAxa because Xap was one of pathogenic strains of Xa,and the whole genome of Xap 9-4 preserved in our laboratory was used as template for amplification to obtain the gene sequence of xopA of Xap.Then,bioinformatics analysis was performed on the XopAXap protein.Results found that the protein,with a molecular weight of 13314.53 Da and 129 amino acid residues,was an acid and hydrophilic protein with an isoelectrical point of 3.47,rich in glycine and containing 2 a-helical regions,which basically meet the characteristics of other harpin proteins in Xanthomonas.The protein was expressed in E.coli and its biological characteristics were tested.It was found that XopAXap with a concentration of 10 μg/ml induced hypersensitive reaction of tobacco at 36 hours post inoculation,and it still had the ability to stimulate HR after 10 minutes of water bath at 100℃.However,this ability disappeared after the treatment by protease K for 30 min,which indicated that XopAxap was a heat stable protein but sensitive to protease,and subcellular localization analysis showed that XopAXap may be located in the intercellular space.These properties were in accordance with those of harpin protein of Xanthomonas. |
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