|STEKETEE, CLINTON - University Of Georgia|
|MARTINEZ-ESPINOZA, ALFREDO - University Of Georgia|
|HENRY, GERALD - University Of Georgia|
|RAYMER, PAUL - University Of Georgia|
Submitted to: International Turfgrass Society Research Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/1/2016
Publication Date: 8/17/2017
Citation: Steketee, C.J., Martinez-Espinoza, A.D., Harris-Shultz, K.R., Henry, G.M., Raymer, P.L. 2017. Evaluation of seashore paspalum germplasm for resistance to dollar spot disease. International Turfgrass Society Research Journal. 13:1-10.
Interpretive Summary: Seashore paspalum is a turfgrass often grown as a single clonal cultivar on golf courses and recreational fields. Dollar spot, caused by the fungus Sclerotinia homoeocarpa, reduces the quality and playability of seashore paspalum and fungicides are commonly used to manage the disease. Yet resistance to some of the fungicides has been documented and thus a large number of plants were screened to identify accessions with host plant resistance. Ninety seashore paspalum accessions were obtained commercial sources, from the USDA Plant Genetic Resources Conservation Unit, and the University of Georgia. Each accession was rated for dollar spot damage after natural infestion or after incoculation with Sclerotinia homoeocarpa. From 2013 to 2015, disease severity was rated six times and accessions with the lowest disease ratings were Spence, FR-4, and PI 647907 whereas accessions with the highest disease ratings were PI 576138, Kim1, and PI 509018-2. This information can be utilized for the recommendation of commercial cultivars in areas prone to dollar spot, for genetic mapping of dollar spot resistance using parents with the most contrasting phenotypes, or this information can be used by plant breeders that can utilize some of the resistant accessions in their breeding programs.
Technical Abstract: Development of seashore paspalum (Paspalum vaginatum Swartz) cultivars that exhibit resistance to dollar spot disease, caused by Sclerotinia homoeocarpa F.T. Bennett, are needed. Seashore paspalum is a warm-season turfgrass often utilized on golf courses and athletic fields in the southeastern United States and other warm temperate regions of the world. Dollar spot is a significant fungal disease that causes turf quality and playability issues on fine-textured paspalum. Management of dollar spot on seashore paspalum currently relies primarily on fungicides, but resistance to fungicides has been documented, leading to a need for improved host plant resistance. Ninety P. vaginatum accessions assembled from the USDA germplasm collection, commercially available cultivars, and University of Georgia experimental lines were screened in the field after natural S. homoeocarpa infections and using an artificial inoculation procedure for the dollar spot resistance. These accessions were evaluated visually and by using digital image analysis for percent disease development over time. The experiments were conducted to find seashore paspalum germplasm with improved genetic resistance to dollar spot disease that could be used in a breeding program. In general, percent disease varied significantly among the accessions with no discrete classes, indicating resistance to S. homoeocarpa in seashore paspalum is likely quantitative with several genes influencing resistance or susceptibility. Several genotypes evaluated as part of this study show promise of improving host plant resistance if used in crosses with elite seashore paspalum germplasm.