Diversity Of Rhizoctonia Cerealis Vander Hoeven And Molecular Diagnose

171 Rhizoctonia isolates were obtained from sheath of infected wheat, which were collected from different areas of Jiangsu province in 2001, and the identification results revealed that, among these isolates, 169 isolates were binucleat Rhizoctonia, the percentage was 98.83%, 2 isolates were multinucleat Rhizoctonia. Among the binucleat Rhizoctonia, 158 isolates were CAG1 anastomosis group (Rhizoctonia cerealis Vander Hoeven), and the other 11 isolates were other anastomosis groups. The 2 isolates of multinucleat Rhizoctonia were AG2 anastomosis group of Rhizoctonia solani K hn.The pathegeniciry of all the isolates were evaluated in three wheat varieties with artificial inoculation method. The results showed that virulence of all these isolates were significantly different. The virulence of binucleat Rhizoctonia isolates was higher than R. solani, while no significant difference were observed among different anastomosis groups of binucleat Rhizoctonia. Isolates from 13 cities differed significantly in their virulence. Isolates from Wuxi , Lianyungang , Taizhou, Suzhom Yancheng were highest, while isolates from Nantong, Changzhou were among the lowest.The sequence of rDNA internal transcribed spacer ( ITS ) of seven representative isolates were amplified by PCR using universal primers ITS1( TCC GTA GGT GAA CCT GCG G ) and ITS4( TCC TCC GCT TAT TGA TAT GC ) and were sequenced. The alignment of the isolates tested showed great intraspecific variation in rDNA ITS1-5.8s-ITS2 sequence. Phylogenetic tree was obtained. This dissertation analysised the complexity and diversity of the pathogene caused sharp eyesport in wheat, and helped to study ecology and epidemicology of R. cerealis.According to the difference of rDNA ITS sequence among R. cerealis and R. solani, Helminthosporium spp. , Alternaria spp, Gaeumannomyces graminis var. trifici, Fusarium nivale, 2 pairs of primers were designed for identifying: DNF77: 5' -cac ctg tgc ace tgt tta gac g-3' , DNR5 54: 5' -gtt cat cca tga ate egg cca c-3' and DNF81: tgt gca cct gtt tag acg gt, DNR564: gtt aga age ggt tea tec at. The results showed that a sequence about 480bp could be amplified by PCR from pure cultured Rhizoctonia isolates and infected sheath of wheat by Rhizoctonia isolates, which could be used to develop a rapid PCR-based diagnose test to the sharp eyespot disease at early stage of R.cerealis infesting wheat, and could be applied for inspection and forecast.