12-7 Development of a molecular genetic system in the diploid legume Medicago truncatula .
Legumes are the system of choice for study of both rhizobial and mycorrhizal symbioses.
Plant mutants defective in initiation of these symbioses have been identified in the major crop legume species, including pea, alfalfa and soybean. However, molecular-genetic analysis in these species is difficult due to features such as tetraploidy, large genomes with abundant repetitive DNA, and inefficient methods for transformation and regeneration. Thus, the diploid, autogamous legume Medicago truncatula which is tractable for molecular genetic analyses was proposed as a model for legume biology. To facilitate molecular-genetic analysis in M. truncatula , we have developed efficient methods for mutagenesis and artificial hybridization, identified polymorphic ecotypes, developed simple methods for transformation and regeneration, and created a large insert BAC library. Mapping populations were generated for three nodulation mutants, two of which are altered in mycorrhizal associations.