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Abstract Detail


MSA - Systematics/Evolution

Rodriguez-Carres, Marianela [1], Vilgalys, Rytas [2], Lutzoni, Francois [2], Cubeta, Marc A. [1].

Phylogeny of the Rhizoctonia species complex and closely related taxa.

The Rhizoctonia species complex is composed of genetically diverse fungi in the Ceratobasidiales that include soil saprobes, pathogens of plant in more than 180 families, and symbionts of orchids, liverworts, and mosses. Identification and classification of Rhizoctonia (teleomorphs Ceratobasidium and Thanatephorus) is challenging due to the variability and limited number of morphological characters available, the lack of information about their sexual mode of reproduction, and conflicts among single gene phylogenies. Rhizoctonia anamorphs are often classified into anastomosis groups (AG or CAG) based on hyphal vegetative compatibility assays using predetermined tester strains. Phylogenetic analysis of ITS and LSU regions of nuclear rDNA supported these anastomosis groups as monophyletic. However, these studies also revealed conflicts in the taxonomic delimitation of species due to variable evolutionary rates found in Rhizoctonia and related fungi in the Cantharelloid clade. In the current study we evaluated the phylogenetic relationships of Rhizoctonia by employing a multi-locus sequencing approach. The targeted loci examined included the nuclear coding genes LSU, RPB1, RPB2, EF1∝, EF2∝, MCM7 as well as the ITS region. In addition to Ceratobasidium and Thanatephorus, representatives of Botryobasidium, Sebacina, and Tulasnella usually found as soil saprobes and plant mycorrhizal symbionts, were also sampled. Preliminary results based on a single locus phylogenies indicate that representatives from at least two other genera, Uthatobasidium and Burgoa, formed a monophyletic clade with isolates from Ceratobasidium AG-Q, CAG-1 and AG-D. Given the diverse habitat and economical importance of many of these fungal species, this study will provide new insight into the genetic diversity, evolution, and species boundaries of Rhizoctonia.


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1 - North Carolina State University, Department of Plant Pathology, Raleigh, NC , 27695
2 - Duke University, Department of Biology, 139 Biological Sciences Building, PO Box 90338, Durham, North Carolina, 27708, USA

Keywords:
Rhizoctonia solani
plant pathology
phylogeny
Ceratobasidiales
Cantharelloid
mycorrhizal fungi.

Presentation Type: Oral Paper:Papers for Topics
Session: 55
Location: Cottonwood A/Snowbird Center
Date: Tuesday, July 28th, 2009
Time: 3:45 PM
Number: 55001
Abstract ID:643


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