Medicago truncatula, a relative of alfalfa (Medicago sativa), has been proposed as a model plant system for study of its interaction with the symbiont Rhizobium meliloti. Differences in M. truncatula and alfalfa may result in distinct symbiosis behaviors for the two hosts when in association with wild-type or mutant bacterial strains. We have found that M. truncatula has a more stringent requirement for syrM and nodD3 than is seen in alfalfa. In particular, the lack of syrM is associated with arrested nodule development.
