Comparison of rDNA-ITS Sequences between Potato and Tobacco Strains in Rhizoctonia solani AG-3

Abstract

Genetic diversity among 61 isolates of Rhizoctonia solani AG-3, representing potato and tobacco populations, was inferred from the sequenhes of the internal transcribed spacer (ITS) and 6.8s ribosomal RNA (rRNA) gene. The 6.85 rDNA sequence was completely conserved not only in AG-3, but across all the AG isolates examined, whereas the rDNA-ITS sequence was found to be variable among the isolates. The nucleotide sequence similarity in the ITS 1 region was high (96-100%) for isolates within each of the two populations, but was 91-92% for isolates from different populations. The AG-3 isolates had 66 to 91% sequence similarities in the ITS 1 region with R. solani isolates of the other AGs. Phylogenetic analysis based on the ITS-6.8s rDNA sequence data indicated that the different populations in AG-3 are distantly related to each other. Genetic divergence between the two populations was also supported by the results of DNA-DNA hybridization studies. This study suggests that AG-3 consists of two genetically isolated groups corresponding to separate subgroups: AG-3 PT (potato type) and AG-3 TB (tobacco type). Specific primer sets for the detection of the two AG-3 subgroups were developed from the aligned rDNA-ITS sequences.

Evolutionary Diversification Indicated by Compensatory Base Changes in ITS2 Secondary Structures in a Complex Fungal Species, Rhizoctonia solani

“…Some of the strains infecting tobacco can anastomose with AG-3 strains from potato, but there are also systematic biochemical (Johnk et al 1993) and genetic differences (Kuninaga et al 2000) between potato and tobacco strains, and somatic compatibility groups within the groups of potato and tobacco strains of AG-3 (Ceresini et al 2002a). These results are consistent with those of this study, which indicate that the potato and tobacco strains of AG-3 belong to different species.…”

“…The 80 different ITS sequences available from AG-3 strains in databases showed little variability, except the difference between potato and tobacco strains reported previously (Kuninaga et al 2000;Ceresini et al 2002a). It was considered worthwhile to analyze a larger number of potato strains to capture variability which might affect CBC predictions.…”

“…5). The tobacco strains of AG-3 (Kuninaga et al 2000;Ceresini et al 2002a) differed from potato strains at 35-40 positions. All new strains described here were placed in the potato subgroup.…”

Taxonomic Position of Korean Isolates of Rhizoctonia solani Based on RAPD and ITS Sequencing of Ribosomal DNA

“…Randomly amplified polymorphic DNA PCR (RAPD-PCR) analysis was performed to detect genetic variability among the isolates of R. solani (Sharma et al, 2005). Sequence analyses of the internal transcribed spacer (ITS) regions of ribosomal DNA have been used to study the genetic relationships between AGs of R. solani by many authors (Boysen et al, 1996;Gonzales et al, 2001;Kuninaga et al, 1997;2000;Salazar et al, 1999).…”

A Comprehensive Overview on Black Scurf of Potato

“…AGs have been further divided into subgroups, and subgroups into subsets, on the basis of culture morphology, pathogenicity, host range, nutritional requirements and/or biochemical and genetic properties (Stevens Johnk et al, 1993;Kuninaga et al, 1997Kuninaga et al, , 2000bNicoletti et al, 1999;Carling et al, 2002b). Binucleate Rhizoctonia isolates are associated with diseased potato plants, but cause minimal damage when tested on potatoes (Tsror, 2010).…”