Oral Technical Session: Fungal Disease Control on Monocots

144-O

A new name for an age-old fungus: Unraveling the mystery of dollar spot disease of turfgrass.
L. A. BEIRN (1), L. Tredway (2), M. Boehm (3), A. Orshinsky (4), A. Putman (5), I. Carbone (5), B. Clarke (1), J. A. Crouch (6)
(1) Rutgers The State University of New Jersey, New Brunswick, NJ, U.S.A.; (2) Syngenta Crop Protection, Greensboro, NC, U.S.A.; (3) The Ohio State University, Columbus, OH, U.S.A.; (4) Agriculture & Agri-Food Canada, Saskatoon, SK, Canada; (5) North Carolina State University, Raleigh, NC, U.S.A.; (6) USDA-ARS, Systematic Mycology and Microbiology Laboratory, Beltsville, MD, U.S.A.

Dollar spot is one of the most economically important fungal diseases of warm- and cool-season turfgrass species. Although the pathogen was described as Sclerotinia homoeocarpa, the true taxonomic placement of this fungus has remained unresolved. Previous morphological and rDNA sequence data have indicated that this pathogen is more appropriately placed in the Rutstroemiaceae family rather than the Sclerotiniaceae family; however, additional data is needed to test this theory. In this study, we used molecular data to evaluate 85 isolates of the dollar spot fungus and closely-related fungi in the Rutstroemiaceae (Ciboria, Lambertella, Lanzia, Poculum, Rutstroemia). Partial sequences from eight regions were generated for phylogenetic analysis: actin, β-tubulin, calmodulin, the internal transcribed spacer region (ITS), the large subunit, DNA replication factor Mcm7, TEF1-α, and the small ribosomal RNA subunit. An additional ~200 bp fragment of ITS-1 was amplified from 54 fungarium specimens, including the original specimens used by Bennett to describe the species. This data confirmed that the dollar spot pathogen is not a true Sclerotinia species. Phylogenetic data indicated that two distinct species are responsible for dollar spot disease of turfgrass, and that these fungi are not members of any known genus in the Rutstroemiaceae family. In this presentation, we will discuss the proposed nomenclature for the two causal agents of dollar spot disease of turfgrass.