Pathogenicity and Molecular Phylogeny of Sclerotinia homeocarpa Causing Dollar Spot Disease on Turfgrass

Abstract

Dollar spot symptoms observed on turfgrass systems were investigated to determine the pathogenicity and molecular phylogeny of Sclerotinia homeocarpa, the causal agent responsible for economically important foliar disease in managed turf environments. Field surveys across turfgrass lawns and sports fields revealed small, circular, straw-colored lesions with characteristic hourglass-shaped blighting on leaves, leading to coalescence and extensive turf thinning under conducive environmental conditions. Fungal isolates recovered from symptomatic tissues produced slow-growing colonies with white to tan mycelium on culture media, consistent with morphological descriptions of S. homeocarpa. Pathogenicity assays conducted on healthy turfgrass under controlled humidity and temperature conditions successfully reproduced dollar spot symptoms, confirming virulence and fulfilling Koch’s postulates. Molecular characterization using ITS rDNA and β-tubulin gene sequencing confirmed isolates as S. homeocarpa, showing high similarity with reference isolates from temperate turfgrass regions. Phylogenetic analysis placed all isolates within a well-supported S. homeocarpa clade, indicating low genetic variability and a relatively conserved population structure across sampled locations. Disease development was strongly associated with warm days, cool nights, prolonged leaf wetness, and low nitrogen fertility, which collectively enhanced infection and disease spread. The study highlights the continued significance of S. homeocarpa as a major pathogen in intensively managed turfgrass systems and emphasizes the need for integrated disease management strategies. Recommended approaches include optimized nitrogen fertilization, irrigation management to reduce leaf wetness duration, and strategic fungicide applications to suppress disease outbreaks and maintain turf quality.