Evolutionary Relationships and Salt Tolerance within Medicago

Genome-wide, single nucleotide polymorphisms (SNPs) and germination data were analyzed to better understand species delimitation and salt-tolerance within the legume genus Medicago. Molecular phylogenies revealed that the widely-used, genomic model line R108 and two deeply divergent accessions of Medicago truncatula are in fact more closely related to Medicago littoralis than to other accessions representing Medicago truncatula. This result was supported by germination data wherein the two accessions representing deeply divergent Medicago truncatula demonstrated salt-tolerance that was more similar to Medicago littoralis than to other accessions of Medicago truncatula. Molecular phylogenies revealed that two additional accessions representing deeply divergent Medicago truncatula appear to be more closely related to Medicago italica than to other accessions representing Medicago truncatula. The results of the present study elucidate complex evolutionary relationships and contribute to the present understanding of existing salt-tolerance within Medicago.