Genetic structure of populations ofRhizoctonia solaniAG-3 on potato in eastern North Carolina

Abstract

Abstract:A polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method was developed to identify and differentiate genotypes of Rhizoctonia solani anastomosis group 3 subgroup PT (AG-3 PT), a fungal pathogen of potato. Polymorphic co-dominant single-locus PCR-RFLP markers were identified after sequencing of clones from a genomic library and digestion with restriction enzymes. Multilocus genotypes were determined by a combination of PCR product and digestion with a specific restriction enzyme for each of seven loci. A sample of 104 isolates from one commercial field in each of five counties in eastern North Carolina was analyzed, and evidence for high levels of gene flow between populations was revealed. When data were clone-corrected and samples pooled into one single North Carolina population, random associations of alleles were found for all loci or pairs of loci, indicating random mating. However, when all genotypes were analyzed, the observed genotypic diversity deviated from panmixia and alleles within and between loci were not randomly associated. These findings support a model of population structure for R. solani AG-3 PT on potato that includes both recombination and clonality.

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

“…Taken together, the difficulties with classification of strains of R. solani using the biological, biochemical and molecular criteria available in the past have been widely recognized (Ceresini et al 2002a(Ceresini et al , 2002b(Ceresini et al , 2003González et al 2006;Sharon et al 2008). The results of this study contribute to resolving the R. solani complex by providing novel evidence with strong support from massive analysis of ITS2 sequences, and especially from the CBC analysis.…”

“…The secondary structures of ITS2 RNA provide a rather simple molecular marker, which is particularly useful when studying closely related species (Müller et al 2007) and also organisms such as R. solani whose genetics is otherwise difficult to study. These difficulties with R. solani are associated with (i) heterokaryotization and multinucleate cells with 3-21 nuclei per cell detected in the strains examined in this study and 2-19 nuclei in a potato strain of R. solani studied by Sanford and Skoropad (1955); (ii) the lack of clamp connections in hyphae making it impossible to distinguish homokaryons from heterokaryons and to detect mating reactions (Cubeta and Vilgalys 1997) and (iii) difficulty to produce the sexual, teleomorphic stage (T. cucumeris) and basidiospores in vitro (Ceresini et al 2002b). ITS2 secondary structures provide additional evolutionary information (Coleman 2000(Coleman , 2003Coleman and Vacquier 2002;Schultz et al 2005Schultz et al , 2006Wolf et al 2005aWolf et al , 2005bSelig et al 2008).…”

Intraspecific Evolution of Rhizoctonia solani AG-1 IA Associated with Soybean and Rice in Brazil based on Polymorphisms at the ITS-5.8S rDNA Operon

“…solani AG-1 IA) in Texas (Rosewich et al, 1999) and in India (Linde et al, 2005). A recombining structure was also reported for populations of T. cucumeris from potatoes (anamorph=AG-3 PT) in north Carolina (Ceresini et al, 2002). Although the mating system of T. cucumeris is not known, this strong evidence for recombination indicates that sexual spores play an important role in the fungal life history contributing to the genetic diversity and structure of field populations of the pathogen.…”

An examination of genetic variation and disease spread in Inonotus tomentosus in the sub-boreal spruce zone of British Columbia.

“…Among the six populations of I. tomentosus in this study, marker diversity ranged narrowly from 0.16 to 0.25. This value is consistent with gene diversity measured using multi-locus marker sets for other fungal species which have been found to reproduce both sexually and asexually Goggioli et al 1998;Chen et al 2002;Ceresini et al 2002). Values associated with these measures are not directly comparable between studies because of the inherent differences between marker types and the application of the methods used for each analysis, but from them generalizations can be made regarding relative levels of diversity between organisms (James etal.…”