Pathogenicity And Genetic Diversity Of Rhizoctonia Cerealis And Dsrna Within It

Wheat sharp eyespot is an important soil-borne fungal disease in the winter wheat planting areas. To analyze the structure and virulence, wheat plants showing wheat sharp eyespot symptoms were collected from different areas of Jiangsu, Shandong, Anhui, Henan and Hubei province and the pathogen was isolated. Identification results showed, among the241isolates,237isolates were Rhizoctonia cerealis with percentage of98.34%, and only4isolates were Rhizoctonia solani with percentage of1.66%. All R. cerealis isolates were in AG-D anastomosis group. Among the4isolates of R. solani, based on anastomosis and blast of their ITS sequences, one isolate was in AG-1-IB anastomosis group, and one isolates was in AG-l-IC and two isolates were in AG-5, respectively. The results showed that virulence of these isolates was different significantly.161isolates with percentage of67.93%were moderate virulence (average disease index of19.82-34.70),46isolates with percentage of19.41%were strong pathogenicity (average disease index of36.59-66.75) and30isolates with percentage of12.66%were weak pathogenicity (average disease index of2.87-17.55), respectively, by the DPS (the UPGMA method) analysis. The resistance of8wheat varieties was different. Among the8varieties, CI12633was the most resistant, but Yumai49and Luke were susceptible varieties.SSR markers were used to analyze the genetic diversity of154isolates of R. cerealis. Totally,24polymorphic bands were produced among the isolates. The genetic similarity coefficients (GS) of154isolates were ranged from0.25to1.00. Based on the genetic similarity coefficient, the154isolates were divided into three groups when the coeffient was0.5. The isolates from the same origin did not completely belong to one cluster, which suggested that the isolates were not completely clustered by their origin and an extensive genetic exchage existed among the isolates. Besides, the isolates with the same virulence belonged to one cluster, but the isolates with the different virulence belonged to one cluster sometimes, which suggested that there was no obvious between the virulence of isolates and genetic diversity. The specific primers of M2dsRNA developed in R. solani were used in this study, but these primers were invalid in R. cerealis. The results suggested that specific M2dsRNA did not exist in R. cerealis. DsRNA technical was used to study the dsRNA in R. cerealis. DsRNA were detected in20isolates with weak pathogenicity and21isolates with strong pathogenicity. DsRNA was not detected in only1isolate with strong pathogenicity in this study. These results suggested indicating that the dsRNA in R. cerealis was widespread and its presence or absence had no obvious correlation to the virulence of isolates.