2013 Annual Report
Creeping bentgrass (Agrostis stolonifera L.) is the premier turfgrass species used on golf course putting greens, fairways, and tees. One of the difficulties in determining the progenitors of the cultivated bentgrasses is the lack of accurate ploidy determinations for many of the Agrostis accessions maintained in the National Plant Germplasm System (NPGS). ARS scientists working in Beltsville, MD analyzed 75 Agrostis accessions representing 15 distinct species along with two Apera and four Polypogon accessions using flow cytometry and 1,309 DNA markers. Cluster analysis clearly separated the common turf-type Agrostis species into distinct groups. The inclusion of previously understudied species within these groups offers insights into the genomic origins of creeping bentgrass that will be useful in future breeding efforts. In addition, the data suggest a narrowing of the genetic diverstiy within cultivated creeping bentgrasses.
The turfgrass diseases dollar spot and brown patch, caused by the fungi Sclerotinia homoeocarpa and Rhizoctonia solani, are the most widespread fungal diseases of highly managed turfgrass species such as Creeping bentgrass (A. stolonifera). More money is spent to manage these diseases than all other turfgrass diseases combined. Dollar spot and brown patch are widespread during the summer months in warm humid areas of the United States, and spray programs are generally scheduled at regular intervals to safeguard against disease establishment. However, these spray strategies can lead to the fungi developing fungicide resistance and this has become a major issue in certain regions of the county. ARS researchers at Beltsville, MD are using new high throughput DNA sequencing technologies to determine the genes that are important in the interaction of these important fungal pathogens with turfgrass plants. In order to establish a better understanding of the location of genes that influence dollar spot resistance, two experimental mapping populations were developed and genetic linkage maps created. An experimental mapping population was developed at Rutgers University by crossing a resistant creeping bentgrass plant to a susceptible creeping bentgrass plant. AFLP and SSR genetic markers were then used to develop a linkage map of this population and determine the location of genome regions influencing dollar spot resistance. A second experimental mapping population was also developed at Rutgers that involves a cross between resistant colonial bentgrass and susceptible creeping bentgrass. AFLP markers were also used to develop a linkage map of this cross for determining the genome location of resistance genes. In the future it may be possible to utilize genetic markers for the selection of dollar spot resistance which would dramatically speed up the development of dollar spot resistant creeping bentgrass germplasm and lead to a significant reduction in golf course fungicide applications.