Submitted to: Symposium Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 8/15/2008
Publication Date: 8/20/2008
Citation: Gomaa, N.M., Rothrock, C.S., Jia, Y. 2008. Sequence variation of the rDNA internal transcribed spacer (ITS) region among isolates of Rhizoctonia solani. Proceedings of 4th International Symposium of Rhizoctonia, Aug. 20-22, 2008, Berlin Germany. p. 50. Interpretive Summary:
Technical Abstract: Rhizoctonia solani is a common and highly heterogeneous fungal species. Sub-specific groups have been created based on hyphal anastomosis (AGs). One of the newer AGs described is AG-11 from soybean and rice seedlings or soil in Arkansas and lupine in Australia (Carling et al. Phytopathology 84:1378-1393). The objective of this study was to examine sequence variation of the ITS region among isolates of AG-11 and other selected AGs. The R. solani ITS of rDNA was amplified from genomic DNA by PCR using primers GMRS-4 (YL114: 5’- CGGTTCATCTGCATTTACCTT-3’) and ITS (YL116: 5’- TCCGTAGGTGAACTGCGG-3’). Amplified PCR products (approximately 610 bp) were separated by electrophoresis and cloned into the pCR® 2.1 vector. Five clones from each isolate were sequenced from both directions using primers T7 and M13. The 5.8s region of the rDNA was 154bp for all R. solani isolates examined. The ITS1 region for isolates ranged from 204 to 232 bp. The ITS2 region varied between 258 and 280 bp. Sequence homology for isolates was between 78.1 to 100% for ITS1 and between 99.1 to 100% for ITS2. Phylogenetic analyses of ITS among isolates were conducted using the random tree option of PAUP*4.0. Isolates of the different AGs were found in distinct groups, except for AG-11. The AG-11 isolates exhibited relatively high diversity among the isolates. The Australian isolates of AG-11 formed a distinct cluster with a bootstrap value of 94%, whereas the Arkansas isolates exhibited relatively high heterogeneity. Three of the Arkansas isolates formed a distinct cluster with a bootstrap value of 100%, while the other Arkansas isolates exhibited relatively high divergence among isolates. We suggest that greater diversity for the ITS region may exist within an AG that can be used to monitor molecular evolution of R. solani.