Medicago


Medicago is a genus of flowering plants, commonly known as medick or burclover, in the legume family. It contains at least 87 species and is distributed mainly around the Mediterranean basin. The best-known member of the genus is alfalfa, an important forage crop, and the genus name is based on the Latin name for that plant, medica, from μηδική Median. Most members of the genus are low, creeping herbs, resembling clover, but with burs. However, alfalfa grows to a height of 1 meter, and tree medick is a shrub. Members of the genus are known to produce bioactive compounds such as medicarpin and medicagenic acid. Chromosome numbers in Medicago range from 2n = 14 to 48.
The species Medicago truncatula is a model legume due to its relatively small stature, small genome, short generation time, 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, USDA-GRIN, ICARDA, and INRA.

Evolution

Medicago diverged from Glycine about 53–55 million years ago, from Lotus 49–51 million years ago, and from Trigonella 10–22 million years ago.

Ecological interactions with other organisms

Symbiosis with nitrogen-fixing rhizobia

Béna et al. 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 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 and C. fuscociliella.

Species

This list is compiled from:

Section Buceras

Subsection Deflexae

Subsection Intertextae

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.