Pathogenic Differentiation And Genetic Diversity Of Wheat Sharp Eyespot In Henan Province

The wheat disease samples with typical sharp eyespot from Zhoukou, Anyang,Nanyang etc13 regions in Henan Province were obtained,and then 157 Rhizoctonia strains were isolated.All of the isolates were binucleate Rhizoctonia strains (BNR) identified by the nuclear staining,while 156 isolates belonged to the AG-D anastomosis group,1 was the AG-BO anastomosis group by hyphal anastomosis reaction and rDNA-ITS sequences analysis.The virulence of 113 isolates were tested in greenhouse on 3 wheat cultivars such as Shan 229,Yumai 49 and Ji 5385.The virulence of Rhizoctonia isolates showed significant difference,and Rhizoctonia isolates in Henan could be divided into three pathotypes:the highly aggressive isolates,the moderately aggressive isolates and the weakly aggressive isolates,accounting for 58.40%,35.40% and 6.19% respectively.The results also showed that the virulence of isolates had certain difference among 13 different regions,the isolates from Hebi, Zhoukou and Luohe regeins with the strongest virulence,whereas the isolates from Xinyang region with the weakest virulence.The virulence of Rhizoctonia isolates from the same region had certain difference.The virulence of Rhizoctonia isolates on 3 wheat cultivars also had significant difference,the strong virulence on Shan 229 and weak virulence on Ji 5385.29 Rhizoctonia isolates with typical and incomplete hyphal anastomosis reaction, were chosen and sequenced their rDNA-ITS,and the sequence of internal transcribed spacer 1 (ITS1) with 212bp,the sequence of 5.8S with 153bp,the sequence of internal transcribed spacer 2 (ITS2) with 234bp.The ITS1-5.8S-ITS2 sequences analysis showed that the regions of 5.8S were very conservation,while the regions of ITS1 and ITS2 were high variation.The homology analysis of the ITS1-5.8S-ITS2 sequence for R. cerealis through unweighted pair group method (UPGMA) showed that the rDNA- ITS sequence showed high difference among different anastomosis group isolates, whereas the rDNA-ITS sequence showed very conservation among the same anastomosis group isolates. The ISSR-PCR reaction system were optimized ,and 7 ISSR primers were screened from 52 ISSR primers and were used to amplify 119 isolates from 13 regions in Henan Province.The data were analyzed by popgene1.32 soft.The mean of genetic diversity in the regions(Hs) was 0.1513,mean of region genetic coefficient of differentiation(Gst) was 0.3046,and gene flow(Nm) was 1.1416.The result demonstrated certain genetic diversity in the 13 regions,certain genetic variation among the populations,and frequent gene flow among the isolates of the 13 regions in Henan Province.The date were analyzed by NTSYSpc2.10e soft.The result of the clustering and analysis showed R. solani and R. cerealis were divided into two groups in the similarity coefficient 0.52.Which indicated obvious differentiation between R. solani and R. cerealis. R. cerealis were divided into three groups in the similarity coefficient 0.67,with one group AG-BO and the others AG-D.Which also indicated certain differentiation between different anastomosis groups.When the similarity coefficient was 0.82,the isolates of Nanyang region were clustered into one group and the others regions' isolates were separated into different groups.Which indicated the isolates of Nanyang region was alone,and the gene flow of other regions' isolates was very frequently.