Systematic Identification Of Potato Scab Pathogen AMCC400023 And The Genomic Analyses On Its Pathogenicity Island

Potato,the world’s fourth largest food crop after wheat,rice and corn,is widely planted in global scale.China is the world’s largest potato producer and consumer,and list potato into staple food grain as a national strategyin 2015.Potato common scab is an economic disease caused by phytopathogenic Streptomyces spp.,which occurs in potato growing areas of the world and has a tendency to increase year by year.In this study,the pathogens from the potato tubers of suspected scab disease from Fujian,Guangdong and Tibet were first isolated,and the strains with pathogenic genes were screened out by PCR amplification with the disease-causing genes..The pathogenicity of obtained strains was further verified by the methods of radish seedlings,potato tubers and pot experiments.The whole genome of Streptomyces sp.AMCC400023 strain,which was isolated and preserved in our lab,was sequenced for ANI and isDDH analyses,genome-wide phylogenetic analysis and collinearity analysisin the genome level.At the same time,the PAI composition diagram was constructed.The main results obtained were as follows:138 actinomycetes isolates were obtained from the diseased potatoesin Fujian,Guangdong and Lhasa.The pathogenicity of the isolated strains was verified,and the pathogenic strains were initially identified as Streptomyce turgidiscabies by morphological characteristics and 16 S rRNA analysis.The pathogenicity of Streptomyces sp.AMCC400023 was verified by the methods of radish seedlings,potato tubers and pot experiments.Allthe results showed that Streptomyces sp.AMCC400023 was pathogenic and could form typical scab symptoms.The whole genome of Streptomyces sp.AMCC400023 strain was sequenced.According to the sequencing results,the system molecular biology identification was carried out.The strain waseThe schematic diagram of the PAI composition of Streptomyces sp.AMCC400023 was constructed based on the whole genome level.The PAI of this strain,which consist of toxin region(TR)and colonization region(CR),contained pathogenic genes such as txtAB,nec1 and tomA.At the same time,it was confirmed that Streptomyces sp.AMCC400023 strain could synthesize toxin thaxtomin A by the thaxtomin synthesis experiment..It was conjectured that the PAI of Streptomyces sp.AMCC400023 might be directly or indirectly acquired from S.scabiei 87-22 by horizontal gene transfer(HGT),or at least there were most close homologous relationship between the two pathogens,as indicated by a series of analyses such as phylogenetic relationships among 31 Streptomyces species,ANI and isDDH analyses,PAI structure mapping,thaxtomin A(ThxA)synthetic gene cluster tree construction and most important,the collinearity analysis at the genome level..