Potatoes are widely distributed in more than 150 countries and regions in the world because of their high yield,strong adaptability,and rich nutrition.Streptomyces scabies widely occur in major potato producing areas of the world,which seriously affects the appearance quality and commodities of potatoes value.In this study,the pathogens of potato common scab disease were isolated and identified and pathogenicity was determined in different areas of Inner Mongolia.Identify the species,distribution and dominant species of pathogens,as well as genetic diversity and pathogenicity,and provide theoretical basis for potato common scab control research.The results were as follows:1.Isolation and purification of potato common scab samples collected from 19 cities and flags(counties)in Inner Mongolia.A total of 194 Streptomyces were obtained.There are three types of lesions in the symptoms,which are concave lesions,raised lesions and flat lesions.2.Pathogenicity test results showed that a total of 51 strains among of the 194 strains isolated were pathogenic.These strains could all show pathogenicity to sliced potato and radish seedlings.In the pot experiment.the potato common scab lesions could be produced and 51 strains all contain txtAB gene and tomA gene.and 49 strains contain necl gene.There were two types of pathogenic genes,txtAB+/necl+/tomA+and txtAB+/necl-/tomA+,of which there are 49 strains of txtAB+/necl+/tomA+ and only two strains of txtAB+/necl-/tomA+.It was taken from PSWC-14 in Huhhot Wuchuan,and PSDM-5 in Baotou Damao County.3.Based on the morphology,physiological and biochemical characteristics and molecular biology identification technology,51 isolates of pathogenic Streptomyces were identified,a total of 4 species were identified,of which 34 were identified as S.galilaeus,6 were identified as S.bobili,6 strains were identified as S.scabies,and another 5 strains were an unknown species Streptomyces spp.,but highly related to S.scabies.4.Diversity analysis results show that the types of pathogens in various regions are diverse.S.scabies is the most widely distributed,with the exception of Huhhot and Baotou,all other cities have a distribution of 6 plants,accounting for 1 1.8%of the total.S.galilaeus has the largest number of 34 plants,accounting for 66.7%of the total,and is widely distributed in Hulunbeier,Ulanqab and Huhhot.S.bobili is distributed in Hulunbeier,Ulanqab and Huhhot,with 6 plants,accounting for 11.8%of the total.The unknown species are distributed in Ulanqab City,Huhhot City and Baotou City,with 5 plants,accounting for 9.8%of the total.This shows that S.galilaeus is the dominant species of Potato Scab Pathogens in Inner Mongolia.