2010 Annual Report 1a.Objectives (from AD-416) To identify bentgrass genome regions involved in heat tolerance. 1b.Approach (from AD-416) Two experimental bentgrass populations have been developed at Rutgers University and both will be utilized to identify genomic regions influencing heat tolerance. One population was developed by one cooperator at Rutgers and is designated L-93-10 x 7418-3 this cross is a creeping by creeping cross consisting of 180 pseudo F2 progeny with an additional 450 F3 and backcross progeny are available. A genetic linkage map developed from the 180 pseudo F2 progeny is currently being constructed utilizing SSR markers and AFLP markers generated by the Floral and Nursery Plants Research Unit in Beltsville. Another population developed by another cooperator at Rutgers University is a creeping x colonial hybrid x creeping bentgrass cross designated (Hybrid 15 x 9188) and contains over 500 progeny from which 96 are being used in map development. The linkage map of the (Hybrid 15 x 9188) population is almost complete and contains gene based polymorphisms and AFLP marker produced by the Floral and Nursery Plants Research Unit in Beltsville. Both populations have had preliminary evaluations conducted that indicate the populations are segregating for heat tolerance. Plants of both populations will be maintained under well-watered conditions. Heat stress will be induced by growing plants at a temperature of 35/30 degrees C (day/night) in a large walk-in growth chamber. Turf quality will be rated visually based on a scale of 1-9 (9=best) as an indicator of general turf performance. In addition, several commonly used parameters for phenotyping heat tolerance, including leaf chlorophyll content, leaf photochemical efficiency, and cell membrane stability will be analyzed. The plant phenotyping work will be conducted in another Lab at Rutgers University. 3.Progress Report The objective of this project is to utilize molecular marker approaches to improve selection for heat tolerance in bentgrass. Two bentgrass experimental populations have been phenotyped for characters related to heat tolerance. In addition, molecular markers have been utilized to develop detailed genetic maps of these two populations. The phenotype data on heat tolerance was collected in the summer of 2008 and 2009, with further analysis in 2010. AFLP markers were added to the linkage maps of the two experimental bentgrass mapping populations being used in this study. The data have been used to identify bentgrass genome regions that influence heat tolerance. Currently seven bentgrass linkage groups that contribute to heat and drought tolerance have been identified. Further research will be conducted to determine the level of importance of each of these regions to heat and drought tolerance. The project was monitored by a site visit and monthly phone conversations.