"Rhizoctonia solani AG2-2 is a diverse group of fungi that can cause disease on several economically important crops including sugar beet (Beta vulgaris) and dry bean (Phaseolus vulgaris). Three projects were conducted to help improve understanding of the diversity within the AG2-2 complex. The first project examined the virulence of 44 R. solani AG2-2 isolates on dry beans at both the seedling and adult growth stages. Disease severity ranged from 0.81 to 6.00 for seedlings and from 1.35 to 3.48 on adult plants where 0 = no disease and 6 = plant dead. Isolates in phylogenetic group 1 were, on average, more aggressive at both growth stages. The second project tested the ability of R. solani AG2-2 to cause disease on sugar beets at 11°C. Our results indicate that some isolates can cause considerable disease at temperatures as low as 11°C, which is well below the previously stated minimum of 15°C. Disease severity at 11°C varied from 0.47 to 3.92, where 0 = no disease and 5 = plant dead. The third project involved development of a set of microsatellite markers for R. solani AG2-2. Ten microsatellite loci were identified that were able to distinguish 20 unique genotypes among the 23 representative isolates tested. Groupings based on microsatellite distances largely agreed with the multigene phylogeny of Martin et al. (2014). Overall, R. solani AG2-2 is a highly diverse group and research that examines issues related to host response need to consider this variability. Additionally, knowledge of diversity may be useful in predicting the risk of disease in the field and assist in management decisions such as crop rotation."--Page ii.
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