Selection Mapping: A Powerful Tool for Population Improvement

Genome wide association studies (GWAS) and genomic selection (GS) have been proven to effectively accelerate the breeding process by uncovering genotype-phenotype relationships for favorable traits. Selection mapping represents a complementary approach that can be phenotype-blind, allowing for biological discovery by utilizing a set of selected individuals to assess loci that have been impacted by selection. As opposed to GS, which predicts phenotypes for a pre-selection population, selection mapping involves investigating genetic patterns in a post-selection population to make inferences. This approach allows the identification of loci that have previously advanced a trait, and therefore furthering selection on these loci can lead to further advancement of the desired trait. Using three distinct, densely-genotyped maize populations each subjected to different selection protocols for unique traits, analysis demonstrates that 1) selection mapping provides a powerful approach for utilizing historical populations to uncover loci controlling the traits for which these populations were selected, 2) when coupled with GWAS, selection mapping can provide an independent confirmation of marker-trait associations, and 3) even when GWAS does not identify significant associations, selection mapping can provide insight into the biological reasons for the lack of associations. With the abundance of previously-selected plant and animal populations available, these techniques represent a strategy for leveraging the work of our recent and ancient predecessors to make further phenotypic gains.