Medicago

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 , 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). ==Taxonomy==

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). Species The genus contains at least 87 species. Recent molecular phylogenic analyses of Medicago indicate that the sections and subsections defined by Small & Jomphe, as outlined below, are generally polyphyletic. However, with minor revisions sections and subsections could be rendered monophyletic. • Medicago syriaca E. Small • Medicago truncatula Gaertn. • Medicago turbinata (L.) All. Species names with uncertain taxonomic status The status of the following species is unresolved: from Lotus (deervetch) 49–51 million years ago (also in the Eocene), Etymology The genus name is based on the Latin name for alfalfa, , from Median (grass). ==Distribution and habitat==

The genus is distributed mainly around the Mediterranean Basin, also extending across temperate Eurasia and sub-Saharan Africa. ==Ecology==

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. 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.). ==Agricultural uses==

Agronomic research has been conducted on Medicago species. Other than its best-known member, alfalfa, several of the prostrate members of the family (such as M.&nbsp;lupulina and M.&nbsp;truncatula) have been used as forage crops. Select species in the Medicago genus naturally develop spiney pods during the reproductive phase of growth (such as M.&nbsp;intertexta and M.&nbsp;polymorpha). Despite having high levels of agronomic performance, these are typically viewed as undesirable in sheep based farming systems due to their ability to become lodged in wool, reducing fleece value. Breeding efforts in the 1990s have yielded spineless varieties of burr medic, providing valuable production amongst farming systems in low rainfall (<300mm annual), free draining, alkaline soils. ==Notes==