Medicago

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. The best-known member of the genus is alfalfa ("M. sativa"), an important forage crop, and the genus name is based on the Latin name for that plant, , from Median (grass). 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). Chromosome numbers in "Medicago" range from 2"n" = 14 to 48.
The species "Medicago truncatula" is a model legume 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 and Small and Jomphe 1989. Major collections are SARDI (Australia), USDA-GRIN (United States), ICARDA (Syria), and INRA (France).
Evolution.
"Medicago" diverged from "Glycine" (soybean) about 53–55 million years ago (in the early Eocene), from "Lotus" (deervetch) 49–51 million years ago (also in the Eocene), and from "Trigonella" 10–22 million years ago (in the Miocene).
Ecological interactions with other organisms.
Symbiosis with nitrogen-fixing rhizobia.
Béna "et al." (2005) constructed a molecular phylogeny of 23 "Sinorhizobium" strains and tested the symbiotic ability of six strains with 35 "Medicago" species. 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.
Agricultural uses.
Other than alfalfa, several of the creeping members of the family (such as "Medicago lupulina" and "Medicago truncatula") have been used as forage crops.
Insect herbivores.
"Medicago" species are used as food plants by the larvae of some Lepidoptera species including the common swift, flame, latticed heath, lime-speck pug, nutmeg, setaceous Hebrew character, and turnip moths and case-bearers of the genus "Coleophora", including "C. frischella" (recorded on "M. sativa") and "C. fuscociliella" (feeds exclusively on "Medicago" spp.).
Species.
This list is compiled from:
Species names with uncertain taxonomic status.
The status of the following species is unresolved:
Recent molecular phylogenic analyses of "Medicago" indicate that the sections and subsections defined by Small & Jomphe, as outlined above, are generally polyphyletic. However, with minor revisions sections and subsections could be rendered monophyletic.