Increasing our understanding of the population diversity of Sclerotium rolfsii, the white mold pathogen, in Southeastern peanut production areas

To effectively manage white mold of peanut caused by Sclerotium rolfsii, it is critical that we understand the pathogen's genetic diversity. The goals of this project were to clarify the genetic diversity of S. rolfsii in the Southeastern U.S., and assess this diversity with isolates from around the world. A total of 26 S. rolfsii isolates were collected from Florida, Georgia, Alabama, and South Carolina. Type sequence data was also collected from Spain, Italy, Portugal, Brazil and Chile. DNA was extracted from these isolates and amplified by PCR using ITS, RPB1, RPB2, and MS204 loci. The resulting sequences were aligned and analyzed using Geneious and BioEdit. Phylogenies were constructed with MEGA 7 and a TCS
(Templeton, Crandall and Sing, 1992) population network created in R. Using the 4 loci S. rolfsii isolates where separated into 2 groups with no differentiation related to host or geography. The network analysis using RPB2 indicated that isolates from different Florida counties had different haplotypes, and that the other isolates from Georgia and South Carolina, Europe and South America grouped in different haplotypes as well. This data shows that variation does exists in the S. rolfsii populations, which means pathogen populations should be considered when assessing disease management strategies ( e.g. cultivar resistance).