Travels into Several Rusty Regions of the Wheat Genome.

Global wheat production is consistently challenged by leaf, stem, and stripe rust epidemics, and millions of hectares experience moderate to severe epidemics annually. In order to identify and map effective rust resistance loci, survey the frequency of known resistance genes in global germplasm, and to investigate improved germplasm utilization strategies, over 5000 accessions of tetraploid and hexaploid spring and winter wheat, including the complete National Small Grains Germplasm Core Collection, were genotyped with high-density SNP arrays and screened for resistance to the three rust diseases at seedling and adult plant growth stages through the Triticeae CAP project and complimentary projects.  This research has resulted in discovery of dozens of newly documented resistance loci, provided an assessment of the global distribution of known resistance genes, and enabled research focused on optimal sampling strategies for utilizing genetic diversity in wheat germplasm collections.  Open access to these resources provides a useful foundation for improved sampling of germplasm collections based on genomic predictions. The prediction accuracy of breeding values for rust resistance in core collection accessions are similar to other traits with moderate to high heritability reported to date.  Future research to target valuable repulsion phase linkages, characterize these materials for other important traits, and genotype core accessions with diagnostic markers  will enhance this community resource.  Molecular marker and phenotypic data is available at: http://triticeaetoolbox.org/wheat/ .  Seed of specific lines may be requested through the USDA-ARS National Small Grains Germplasm Collection by visiting: http://www.ars-grin.gov/npgs/searchgrin.html.