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POSTERS: Population biology and genetics

Utilization of microsatellites for Rhizoctonia solani AG2-2 population genetics
Douglas Minier - Michigan State University. Linda Hanson- USDA ARS

Rhizoctonia solani AG2-2 causes Rhizoctonia root and crown rot of sugarbeet (Beta vulgaris) as well as root rots of several other economically important crops. We have developed a set of microsatellite markers to examine diversity and population structure in R. solani AG2-2. We are utilizing these markers to investigate R. solani AG2-2 diversity at varying geographic levels and among isolates recovered from sugarbeet and several rotation crops. To examine the distribution of AG2-2 genotypes in Michigan fields, isolates collected by baiting with toothpicks are being genotyped using eight microsatellite markers. Furthermore, in order to understand how diversity is generated in AG2-2, we need to identify the extent to which recombination occurs. Since AG2-2 rarely produces a sexual stage, genetic material is expected to be exchanged through hyphal fusion. However, anastomosis reactions typically result in death of the cells adjacent to the fusion site. It is therefore unclear how much genetic exchange occurs between isolates. Preliminary evidence from microsatellite loci sequencing shows that isolates from different genetic groups have microsatellite alleles that are identical by sequence, which is suggestive of an exchange of genetic material. To test the extent of asexual hybridization, isolates from different genetic groups were paired on water agar and potential hybrids isolated. Several resultant isolates showed variation in cultural characteristics from the parent cultures indicating possible hybridization occurring. The microsatellite analysis is ongoing.