Genetic Diversity, Population Structure and Genome-Wide Association Studies in a Worldwide Barley Collection of Cultivars and Landraces

New sources of genetic diversity must to be incorporated into plant breeding programs to continue increasing grain yield and quality and to respond to climate changes. Germplasm collections provide a source of genetic and phenotypic diversity, but characterization of these resources is required to increase their utility for breeding programs. We used the 9K-SNP iSelect platform to genotype 2,417 barley accessions belonging to the USDA National Small Grains Collection. Most of the accessions are categorized as landraces or cultivars/breeding lines and were collected worldwide. Principal coordinate analysis and genetic assignment analysis were used to examine the genetic relationships among accessions. Both approaches identified six major populations, mainly differentiated by geographical origin and spike row number. Several traits including aleurone color, awn roughness, growth habit, hull cover, lemma color, row type, spike density and 1000 kernel weight have been measured in the core subset of the collection. These phenotypes are being used for genome-wide association mapping. The SNP genotype data will also be used to identify a mini-core collection that captures the majority of the genetic diversity present in the complete collection. The mini-core will be used to evaluate traits that are difficult or expensive to measure.