Dollar spot caused by Sclerotinia homoeocarpa F. T. Bennett is the most economically important turf disease in North America. Dollar spot resistance in a creeping bentgrass cultivar would greatly reduce the costs and environmental impacts of fungicide application. Not much work has been done to understand the genetic mechanism of resistance to dollar spot in creeping bentgrass. A full-sib genetic mapping population was developed from the cross between the outcrossing clones 372 and 549, which show difference in disease response and multiple traits like growth rate, leaf color and shoot density. For mapping QTL for dollar spot resistance, field inoculations using a single isolate have been done on 697 progeny at two locations in WI in 2004 and one location each in WI and IL in 2005. For QTL analysis, single marker analysis was done on 697 progeny while interval mapping and composite interval mapping were performed on 94 progeny. One major QTL for dollar spot resistance on LG 7 and three minor QTLs on LGs 2, 3, and 6 have been detected in 2004 and again in 2005. The major QTL had a LOD value ranging from 3.6 to 8.2 and explained 25 to 31% of the phenotypic variance. Its consistency across two years, locations and rating dates indicate that it is stable over environments. The minor QTLs were influenced by rating dates and environments. A sequence characterized amplified region (SCAR) marker tightly linked to the major QTL was developed, and it will be useful in marker assisted selection in bentgrass.
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