Diversity And Main Pathogenic Types Of Pathogen Isolates From Potato Scab In China

Potato common scab is a soil-borne plant disease caused by Streptomyces spp.which belonging to Actinomycetes and is widely distributed in various potato planting areas all over the world.The surface of potato tubers infected by the pathogen of scab could form a red brown irregular spot,which cause a substantial reduction in production of potato and bring serious economic losses.Some potato growing areas in C hina are deeply affected by the disease and have a tendency to increase in these years.In this study,samples were collected from nine provinces and regions in four potato growing areas in C hina.The bacterial strains were isolated and purified,and the strains were systematically identified by physiological,biochemical,morphological,and molecular biological methods.The tuber slices and radish seedling were used to verify the pathogenicity of the strains.The results of the research are as follows:(1)Samples of potato scab were total 26,the type of scab lesions includes netted,raised,pitted and sufferical.(2)Separating and purifying the pathogens of potato scab,206 actinomycetes were obtained,and 68 strains of pathogenic Streptomyces were obtained,the rate of separation was about 33.0%.The identification results showed that Streptomyces including S.bobili,S.galilaeus,S.scabies,S.acidiscabies and S.bottropensis.And the main bacteria were S.cabies.The type of pathogenic bacteria in each region were as follows: Jilin Province was S.acidiscabies(12 strains);Fujian Province was S.scabies(7 strains);Hunan Province was S.scabies(10 strains);Yunnan Province was S.scabies(3 strains),S.bobili(2 strains)and S.galilaeus(1 strain);Anhui Province was S.scabies(1 strain);N ingxia Province was S.scabies(21 strains);Shanxi Province was S.bobili(8 strains);Hubei Province was S.bottropensis(3 strains).(3)The results showed that the composition of pathogenic genes which in pathogenicity islands(PAI)of Streptomyces was diversity through the detection of the pathogenic genes(txt AB,nec1,tom A).Genotypic in pathogenic islands of Streptomyces was diversity.Two kinds of pathogenic genes were detected including txt AB+/nec1+/tom A+ and txt AB+/nec1-/tom A-.(4)In the pathogenicity test,the pathogenic Streptomyces could be colonized on tuber slices and produced dark brown necrotic spots,all of them showed obvious inhibitory effects on the growth of radish seedlings.