Medicago (family: Fabaceae, the legume family) is a genus of flowering plants, commonly known as medick or burclover. The best known member of the genus is alfalfa (M. sativa), an important crop. The species Medicago truncatula is a model legume due to its relatively small stature, genome (450-500Mb), short generation time (~3 months) and ability to reproduce both by outcrossing and selfing.
The Medicago genus contains 83 species, including the agriculturally important alfalfa (Medicago sativa), and is distributed mainly around the Mediterranean basin. Comprehensive descriptions of the genus are Lesins and Lesins 1979 and Small and Jomphe 1989. Major collections are SARDI (Australia), USDA (USA), ICARDA (Syria), and the INRA collection in Montpellier (FRANCE). A molecular phylogeny containing 63 species is available (Bena et al. 2001).
Most members of the family are low, creeping herbs. However, alfalfa grows to a height of 1 meter, and Tree Medick (M. arborea) is a shrub.
Bena et al. (2005) constructed a molecular phylogeny of 23 Sinorhizobium strains and tested the symbiotic ability of 6 strains with 35 Medicago species. Comparison of these phylogenies indicates many transitions in the compatibility of the association over evolutionary time. Furthermore, Bena et al. propose that the geographical distribution of strains limits the distribution of particular Medicago species.