Diversity Analysis Of Potato Common Scab Pathogens In Northern China And Molecular Detection Of Pathogenic Strains

Potato common scab is a soil-borne disease caused by plant pathogenic Streptomycessp., and is spreaded in potato producing areas worldwide. The disease showed scab-likelesions on the surface of potato tubers, which reduced the economic value of thecommodity potato, moreover, diseased potato seeds further accelerate the spread of thepathogens by seeds transporting. In the resent years, due to the rapid development of thepotato industry in China, the incidence region and hazards continue to increase. It isessential to analyze the composition of the scab strains in time. Because the traditionalmethod of detecting pathogenic strains took a long time, we analyzed the molecular geneticcharacteristics of the pathogenic strains in the present study, and explored a moleculardetection method of the pathogenic strains, aimed at clarifying the scab pathogen strainspresent in our country and obtaining efficient detection method.In this study, scabby potato tubers were collected from the main potato producingareas in northern China from2008to2012. One hundred and eighty-three Streptomycesstrains were obtained after isolating and purifying. The pathogenicity of the strains wasverified through Koch’s rule in greenhouse, and found forty-two strains could inducetypical scab symtoms. All of the pathogenic strains were identified according to thebiological characteristics and16S rDNA sequence adjacent cluster analysis. The resultsshowed these strains belonged to six kinds of Streptomyces species, there are15strainsbelonged to S. scabies and S. europaeiscabies,17belonged to S. galilaeus,2belonged to S.turgidiscabies,3belonged to S. enissocaesilis,2belonged to S. diastatochromogenes andthree were unidentified. Which indicated genetic diversity was existed among commonscab pathogen strains, and the domainant species were Streptomyces galilaeus,Streptomyces scabies and S. europaeiscabies in northen China.In order to shorten the time in pathogenic strains screening, five pair primers weredesigned or referenced according to different gene in toxins gene clusters which specific toscab pathogens, and were used to detecting forty-five pathogenic strains and forty-five nonpathogenic strains which isolated from scabby tubers. The results showed that in all45pathogenic strains, the detection efficiency and fragment length of primersTxtAB1/TxtAB2, TxtA1/TxtA2, Bu/Bd, Nf/Nr and Tom3/Tom4were100%and385bp,100%and398bp,84%and1470bp,91%and700bp,89%and392bp, respectively.Wherears, all of the nonpathogenic strains can not amplificated the objective bands. Thatmeans these five primers can be used to screening pathogenic strains. By using this methodand Koch’s rule to test12Streptomyces strains isolated from potato scab lesions, fourpathogenic strains were screened and two methods have consistent results. Which proofedthe molecular screening method established in this work can be used for screening thepathogenic strains of potato common scab.