Segmental Duplication

Medicago, like many other legumes, has a whole genome duplication event (aka polyploidy) within its lineage. This particular WGD event is dated to have occurred approximately 58 million years ago and contributed significantly to the genome we see today. The increase of duplicate genes and subsequent functional divergence might have supported the evolution of nodulation and symbiotic nitrogen fixation.

Conserved blocks, sometimes as large as chromosome arms, span major portions of the euchromatin. The figure below illustrates the types of macrosyntenic relationships between the medicago chromosomal regions.

A given Medicago region is typically syntenic with one other Medicago region (though usually in small blocks showing degraded synteny), four Glycine max regions, one or two Lotus japonica regions, and three Vitis vinifera regions (dot plots not shown).