Population Diversity Of Puccinia Striiformis In Tibet

The assessment of the genetic diversity of tatally 70 isolates of Puccinia striiformis respectively from Tibet and neighbouring areas in Sichun and Yunnan provinces was conducted on the basis of their virulences to the differencial host varieties of Chinese physiologic races of yellow rust fungus and AFLP polymorphism. Totally 23 virulent tpes were identified, of which, Su-2 and S-5 were the predominant races in Tiebet. Cluster analysis of the virulence pattern of the tested 70 isolates to the differential varieties showed that different virulent there were distinct virulent types for Tibet where they were evolved slower.4 pairs of AFLP primers linked to EcoRâ… /Mseâ… restrict enzyme combination were selected for the yield of good polymorphism. Totally 141 AFLP bands including 39 polymorphic bands were detected. The polymorphic rate was up to 27.65%. The cluster analysis of the tested 70 isolates based on the data of AFLP showed genetic diversity in the yellow rust fungal population in Tibet and the variations between sampling sites and years. The genetic similarity indexes also clearly indicated the migration of the isolates between different locations. The Group B,Das well as the Subgroup IV in Group A were distinct genetic types in Tibet but the genetic similarity in Subgroup 1,2 and 3 in Group A also suggested the possibility between the gene flow between Yibetan rust fungal population and the neibouring populations in Sichuan and Yunan provinces. Although virulence assay and AFLP analysis both indicated the independence of the Tibetan yellow rust fungal populations and potential gene flow to and from the neibourong populations in Sichuan as well as Yunan Provinces, it failed to find the characteristic AFLP fingerprints for any special virulent type.