Sequence-Based Map Development of Wheat NAM Populations

Nested association mapping (NAM) combines the advantages of both linkage and association mapping in order to dissect complex traits in a single unified mapping population. Here, we report on the development of the spring wheat NAM population that will be used as a community resource to aid important agricultural trait locus identification and dissection in wheat. The spring wheat NAM population was derived from a diverse set of 32 founders, implementing the common parent design where all founders are crossed to the Berkut accession. Populations of Recombinant Inbred Lines (RILs) from the resulting F1s were selfed for 7 generations to produce 32 separate populations of 75 individuals each, resulting in a final population of 2,400 individuals. All individuals and founders were genotyped using the Illumina 90K iSelect assay, and were subjected to genotype-by-sequencing (GBS) to produce dense genetic maps of ~23, 000 markers per population. Each founder line has been re-sequenced using the 107 Mb whole exome capture (WEC) assay to generate a haplotype map of the wheat genome. The common SNP markers shared between the genetically mapped SNPs in the NAM population and a haplotype map were used to project SNPs from the haplotype map to each NAM RIL creating a dense sequence-based SNP map of wheat available for association mapping. Details of population construction, marker identification, LD patterns, and map development will be presented, as well as examples of how this resource can assist in studying the genetics of complex traits in wheat.