Medicago is a genus of flowering plants, commonly known as medick or burclover, in the legume family (Fabaceae). It contains at least 87 species and is distributed mainly around the Mediterranean basin.[2][3] The best-known member of the genus is alfalfa (M. sativa), an important forage crop,[4] and the genus name is based on the Latin name for that plant, medica, from Greek: μηδική (πόα) Median (grass).[5] Most members of the genus are low, creeping herbs, resembling clover, but with burs (hence the common name). However, alfalfa grows to a height of 1 meter, and tree medick (M. arborea) is a shrub. Members of the genus are known to produce bioactive compounds such as medicarpin (a flavonoid) and medicagenic acid (a triterpenoid saponin).[3] Chromosome numbers in Medicago range from 2n = 14 to 48.[6]
The species Medicago truncatula is a model legume[7] due to its relatively small stature, small genome (450–500 Mbp), short generation time (about 3 months), and ability to reproduce both by outcrossing and selfing.
Comprehensive descriptions of the genus are Lesinš and Lesinš 1979[8] and Small and Jomphe 1989.[9] Major collections are SARDI (Australia),[10] USDA-GRIN (United States),[11] ICARDA (Syria),[12] and INRA (France).[13]
Medicago diverged from Glycine (soybean) about 53–55 million years ago (in the early Eocene),[14] from Lotus (deervetch) 49–51 million years ago (also in the Eocene),[14] and from Trigonella 10–22 million years ago (in the Miocene).[15]
Béna et al. (2005) constructed a molecular phylogeny of 23 Sinorhizobium strains and tested the symbiotic ability of six strains with 35 Medicago species.[16] Comparison of these phylogenies indicates many transitions in the compatibility of the association over evolutionary time. Furthermore, they propose that the geographical distribution of strains limits the distribution of particular Medicago species.
Other than alfalfa, several of the creeping members of the family (such as Medicago lupulina and Medicago truncatula) have been used as forage crops.[citation needed]