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

Potato,wheat,rice,corn and sorghum are known as the world's five crops.China has been the largest potato producing country in the world.At the same time,China is actualizing the strategy of changing potato as the staple food.By the year 2020,potato planting area would expand to more than 16 million acre Potato common scab(PCS)is caused by plant pathogenic Steptomyces spp.,and it's a serious soilborne,filamentous,saprophytic disease in potato production.The disease is prevalently and tends to gradually increase in China and the world.The main purpose of this study was to isolate and identify the pathogen causing PCS in Shandong Province.The isolated strain from potato scab lesions was analyzed and identified by PCR detection of pathogenic genes,morphological observation,mensuration of physiological and biochemical characteristics and determination of molecular biology.Pathogenicity test items consist of potato slices assay,radish seedling assay as well as pot experiments,The main results were as follows:(1)In Shandong,the main lesions of PCS were classified into four types,named raised lesions,pitted lesions,superficial lesions and netted lesions,respectively.And the most of areas contain four types of scab lesions.(2)The different types of scab lesions in each region were tested for the isolation,purification and identification of Steptomyces spp..In total,536 isolates of actinomycetes were obtained from 42 different samples,among which 62 isolates were pathogens of PCS.The separation rate was 11.6%.There were at least two pathogens in Shandong,that was,S.scabies and S.acidiscabies,and the latter was the main pathogen of PCS in Shandong Provence.The pathogens acquired from Tengzhou,Jiaozhou and Taian were S.acidiscabies.The pathogens acquired from Weihai were S.scabies.There were two strains obtained from Gaomi,S.scabies and S.acidiscabies.(3)Through the detection of three pathogenic genes txtAB,necl1 and tomA of PAI,it was found that the genotype of PAI was diverse.Three different pathogenicity island(PAI)genotypes were detected amongst the txtAB positive isolates: txtAB+/nec1+/tomA+,txtAB+/nec1+/tomA-and txtAB+/nec1-/tomA-.(4)Pathogenicity tests showed that the test strains can make small potato slices produce brown necrotic spots,inhibit the growth of radish seedlings,and produce scab symptoms on potato tuber in pot experiment.(5)S.scabies and S.europaeiscabiei can not be effectively discriminated by 16 S rDNA sequencing due to the high similarity of 16 S rDNA of them.So a restriction fragment length polymorphism analysis was required.HPY99 I restriction endonuclease digestion results showed that the isolated pathogen was identical to the standard strain of S.scabies.So the isolated pathogen was S.scabies...