Population Structure and Genome Wide Association Mapping for Diseases Resistance in the Ndsu Barley Breeding Lines.

A comprehensive approach to validate Quantitative Traits Loci (QTL) across diversified germplasm might be a way forward to identify markers that can be broadly deployed by breeding programs for variety improvement. Genome-wide association mapping (GWAM) across a range of genotypes provides an alternative tool to bi-parental mapping studies.  This study was conducted with the objective to identify marker-trait associations for disease resistance traits using GWAM of selected six-and two-rowed barley (Hordeum vulgare L.) lines from the North Dakota State University (NDSU) barley breeder program included in 2006-2009 USDA-CSREES Barley CAP project. All lines had been previously genotyped by the USDA-ARS molecular marker lab in Fargo, ND using 3072 SNPs from oligo pool assay platforms BOPA1 and BOPA2. The software STRUCTURE was used to select two new mapping panels of 90 breeding lines, from a starting population of 384 lines, that maximized genetic diversity within each row type.  The six-and two-rowed lines were analyzed in separate experiments.  Disease screening of the two mapping panels and checks was conducted in the greenhouse.  Entries were assigned to experimental unit using a Randomized Complete Block Design, with each entry replicated three times. Diseases tested included spot blotch, the spot and net-form of net blotch, and barley leaf rust. Association Mapping analyses were done using Proc Mixed from SAS 9.3.  Marker-trait association significance was determined at multiple p-values (≤0.001) and pFDR (0.1). Results for the analyses done on the six- and two-rowed mapping panels will be presented