2006 Annual Report 4d.Progress report. This report serves to document research conducted under Specific Cooperative Agreement no. 58-5442-5-343 between ARS and the University of Minnesota, Department of Agronomy & Plant Genetics. Additional details of research can be found in the report for the parent CRIS 5442-21000-030-00D, "Using Genomics and Genetics to Enhance Disease Resistance and Quality in Hard Red Spring and Durum Wheat." The goal of this project is to enhance marker coverage and density for several barley mapping populations using DArT technology to increase the pool of markers available for marker assisted selection. To date, we have evaluated one Fusarium head blight mapping population using DArT. This population was created with the FHB resistant variety Atahualpa and elite Minnesota breeding line M81. The previous map consisted of 117 simple sequence repeat (SSR) markers, spanned 448 cM of the genome, and took several years to construct. Using the DArT technology, we identified 283 additional markers that were polymorphic between the parents and used them to update the map. In the enhanced map, we increased the genome coverage to 780 cM, a 74% increase. Preliminary QTL analysis with the updated map did identify the major QTL for FHB that was identified using the previous SSR map, but no new large effect QTL. This QTL on bin 10 of chromosome 2H has been identified in other studies and may be important for FHB resistance. Unfortunately, the phenotypic expression of the vrs1 gene in that region that controls two-rowed / six-rowed spike morphology may confound measurements of resistance. Thus, until fine mapping and recombinants that separate the two rowed allele at vrs1 from resistance are found, this QTL will not be useful for six-rowed barley breeding. We will continue analyzing this data set to see if smaller effect QTL will be useful for MAS. Several additional mapping populations will be sent for DArT genotyping to enhance genetic maps once the company that conducts the DArT analysis updates their format for marker screening (in progress).