The Identification of SSR QTL Markers for Dollar Spot Resistance in Creeping Bentgrass.

One of the major challenges in breeding creeping bentgrass (Agrostis stolonifera L.) is improving disease resistance.  Dollar spot disease, caused by the fungus Sclerotinia homoeocarpa F.T. Bennett, is one of the most important diseases of creeping bentgrass. The goal of this research project is to create a genetic linkage map of creeping bentgrass and identify Quantitative Trait Loci (QTL) associated with dollar spot disease resistance.  A mapping population of creeping bentgrass generated from a cross between a dollar spot resistant and susceptible genotype was developed.  Additionally, two backcross populations and a pseudo F₃ population were also developed to confirm the QTL identified in the original population.  Replicated, mowed spaced-plant trials of the pseudo F₂, pseudo F₃ and backcross populations were inoculated with a virulent isolate of S. homoeocarpa on June 30, 2003 (Crenshaw isolate – isolated from Crenshaw creeping bentgrass) and inoculated with a different virulent isolate (PRG isolate – isolated from perennial ryegrass) in a separate study on June 24, 2006.  These spaced-plants were evaluated throughout the growing seasons (2003 and 2004 for the Crenshaw isolate and 2006 and 2007 for the PRG isolate) for dollar spot disease using a 1-9 rating scale.  Initial genetic linkage maps of each original parent were developed using approximately 200 unique SSR markers that were generated in our laboratory.  Four putative QTL markers were identified for the Crenshaw isolate and one different putative QTL marker was identified for the PRG isolate.  This research will be useful in improving our understanding of and breeding for dollar spot disease resistance in creeping bentgrass.