New approaches to an old problem: Dollar spot of turfgrass.

Dollar spot, caused by the fungal pathogens Clarireedia spp. (formerly Sclerotinia homoeocarpa), is the most common and widely distributed disease of turfgrass worldwide. It can drastically reduce the quality of turfgrass species and impact their aesthetic value and playability. Management of dollar spot typically includes a costly program of multiple applications of fungicides within a growing season. Consequently, there have been reported cases of fungicide resistance in populations of Clarireedia spp. Host resistance could be an important component of dollar spot management; however, this approach has been hampered by the lack of sources of resistance as nearly all known warm- and cool-season turfgrass species are susceptible. With the recent advancement in genome sequencing technologies, studies on pathogen genomics and host-pathogen interactions are emerging with the hope to reveal candidate resistance genes in turfgrass and genes for virulence and pathogenicity in Clarireedia spp. Large-scale screening of turfgrass germplasm and quantitative trait loci (QTL) analysis for dollar spot resistance are important for resistance breeding, but only a handful of such studies have been conducted to date. This review summarizes currently available information on the dollar spot pathosystem, taxonomy, pathogen genomics, host-pathogen interaction, genetics of resistance, QTL mapping, and also provides some thoughts for future research prospects to better manage this disease.