Population Genomics in the Model Legume, Medicago truncatula

The role of geography has become established as a central issue in studies of coevolution. Modern sequencing approaches now allow for the examination of coevolutionary selection at the molecular level. Towards this goal, a population genomic analysis was conducted in the model legume, Medicago truncatula, to assess the scale of population genetic structure and scan the genome for symbiosis related genes that have been under selection. Using RAD-seq over 26,000 SNPs were generated from 192 individuals from 12 sampling sites within the native range. STRUCTURE analysis has revealed 5 distinct clusters underlying these accessions. Approximately 70 loci were identified as genomic outliers, including the symbiosis gene, DMI1. This work sets the stage for corresponding studies of genetic structure in the associated rhizobium and can shed light on the mechanisms that maintain genetic variation within this mutualism.