Molecular Linkage Map of the Model Legume Medicago truncatula Gaertn.

The need for a more sustainable and environmentally safe agriculture has reinforced interest in the cultivation of legumes, which include important agricultural species such as alfalfa, clover, pea, soybean, bean, peanut, and more. These species have the capacity to establish an atmospheric dinitrogen fixing symbiose with soil bacteria collectively named rhizobia, and to form symbiotic root mycorrhizae with soil fungi, thus facilitating their uptake of phosphate, water, and other soil nutrients (Albrecht et al. 1999). However, genetic analysis of these processes remains difficult in the major crop legumes due to features such as tetraploidy, large genomes and/or the lack of efficient methods for transgenesis. Since the model plant Arabidopsis thaliana (as indeed is true of other Cruciferae) is unable to establish either rhizo-bial or mycorrhizal symbioses, the need to establish a model legume to analyze plant physiological processes which cannot be satisfactorily studied in A. thaliana has been recognized for over a decade (Cook and Denarie 2000).