Population structure of Sclerotinia homoeocarpa from turfgrass

Abstract

The purpose of this research was to determine population structure of Sclerotinia homoeocarpa, the causal organism of dollar spot, from turfgrass worldwide. Sclerotinia homoeocarpa is prevalent throughout the entire world and more money is spent controlling dollar spot than any other turf disease. The lack of disease cycle knowledge coupled with increased levels of fungicide resistance make understanding the genetic diversity of this fungus vital to ensure acceptable levels of control in the future. One hundred and nine isolates of S. homoeocarpa were obtained from the United States, Dominican Republic, Chile, Italy, United Kingdom and Japan. Isolates were analyzed using nuclear DNA from the ITS, β-tubulin, Calmodulin and TEF1-α loci. The nuclear DNA data suggests strong subdivision of S. homoeocarpa isolates based on host species, with isolates from warm season hosts and isolates from cool season hosts being genetically distinct. Vegetative compatibility tests for the 109 isolates were also utilized to determine the ability of individuals within the population to form heterokaryons with other individuals. Isolates in the study were compared to previously determine vegetative compatibility groups (VCGs) as well as tested with one another. The VCG work resulted in 9 previously unidentified VCGs. Isolates from warm season host species and isolates from cool season host species belonged to separate VCGs, supporting the subdivision seen in the nuclear DNA data. This work has shed new light on the population structure of Sclerotinia homoeocarpa and could potentially lead to alterations in control recommendations of dollar spot.