Pathogen Detection Of Potato Black Scurf In Soil And Evaluation Of Potato Cultivars Resistance To Rhizoctonia Solani

Potato black scurf mainly caused by Rhizoctonia solani anastomosis group 3(AG3)is a typical soil-borne disease,which is threatening the production of potato.Sclerotia are the main survival structure of R.solani in soil and the primary inoculum of potato black scurf.The incidence and severity of potato black scurf are affected by the density of sclerotium in soil directly.Hence,detection of sclerotium density in soil before planting is necessary to provide theoretical basis for the early monitoring and prevention of potato black scurf.Compared with agriculture control,chemical control and biology control,planting disease-resistant varieties can relieve the harm caused by R.solani to potato production fundamentally.China,the largest potato-producing country,has rich potato germplasm resources like Ningshu series,Zhuangshu series,Longshu series,Qingshu series,which are popularized to plant.However,the resistance of these potato varieties to potato black scurf need to be evaluated.In this research,we established a fast method to detect the density of R.solani sclerotium in soil and evaluated the resistance of 52 potato varieties to potato black scurf.The main results of this study were showed as following:1.The SYBR Green I quantitative real-time PCR(qPCR)detection assay for quantification of R.solani AG3 was successfully established using recombinant plasmid which was constructed by the specific band of ITS(Internal Transcribed Spacer)amplified using primer pair RsTqF1/RsTqR1.DNA was extracted by wet-sieving combined with Fast DNA? Spin Kit for Soil and used to get Ct(cycle threshold)value by qPCR.The model of sclerotium density(n)(g/g soil)and Ct value was established as n=10(9.6917-Ct)/3.4558.2.The sclerotium density of soil samples added certain sclerotia was detected by the method of wet-sieving qPCR and selective medium.The result showed that the error range of wet-sieving qPCR and selective medium was 2.77~5.23% and 13.30~33.33%,respectively.There were highly significant differences between the errors of these two methods indicating that wet-sieving qPCR was a more accurate method to detect the sclerotium density in soil.3.The resistance of 52 potato varieties to potato black scurf was evaluated by block experiments in glasshouse.There were some varieties like I46,Zhongshu 3,H29,Longshu 7,Heimeiren,Tianshu 11,Qingshu168,Zhongshu 1,GY013-1 and B25 showing stronger resistance to potato black scurf.On the contrary,Atlantic,Favorita,Helan 15,Xindaping,Qingshu13 and Ningshu 1 were more sensitive to potato black scurf.