Exploiting Barley Germplasm Resources for QTL Detection.

The Triticeae Coordinated Agricultural Project (TCAP) aims to exploit germplasm collections and identify beneficial alleles for barley improvement. The National Small Grain Core Collection (NSGCC) and the wild barley diversity collection (WBDC) are key germplasm resources that have not been fully exploited. The NSGCC is composed of 1860 unique accessions (landraces and historical cultivars/breeding lines) collected from 94 countries and the WBDC is composed of 318 wild barley accessions collected from the wild barley geographical range. To gain access to beneficial alleles in the NSGCC and WBDC, two approaches were used. The NSGCC was genotyped with 7,824 SNPs and a subset of the collection (384 two row spring and 384 six row spring accessions) that encompassed the genetic diversity of the collection was phenotyped for numerous agronomic traits (e.g., height, heading date, tiller number, productive tiller number and other morphological traits). To exploit the WBDC, an advanced backcross nested association mapping (AB-NAM) population was developed. Twenty-five diverse wild barley accessions were backcrossed to the spring six row cultivar Rasmusson to develop 796 BC₂F_4:6 lines. The AB-NAM population was genotyped with over 260,000 markers and phenotyped for numerous agronomic traits (e.g., yield, heading date, height, productive tiller number, wax production). To identify QTL, genome-wide association mapping was conducted on data sets from the NSGCC and the AB-NAM. The utility of these populations will be discussed along with the relationship to previous QTL mapping results.