Plant & Animal Genome VI Conference

W86

DEVELOPMENT AND APPLICATION OF TOOLS FOR GENOME ANALYSIS IN Medicago truncatula

1. Department of Plant Pathology and Microbiology and The Crop Biotechnology Center, Texas A&M University, College Station, USA
2. Institute of Genetics, Biological Research Center, Szeged, Hungary

Medicago truncatula is a small genome, self-fertile, diploid legume species that has been proposed as a model organism for study of symbiotic nitrogen fixation. Over the past few years, the key elements of a tractable molecular-genetic system have been assembled in this species, including for example large collections of symbiotic mutants, EST and BAC libraries, efficient methods for transformation and regeneration, and extensive germplasm collections. In our laboratory we have characterized several Medicago truncatula mutants that are either blocked for early nodule development or that form excessive numbers of nodules, so-called hypernodulators. Based on the absence of early nodulin gene induction, some of the early nodulation mutants are putative Nod factor perception mutants, while one hypernodulation mutant is defective in ethylene perception. To facilitate cloning of these and other legume genes, we are assembling tools for genome analysis in Medicago truncatula. Our current efforts include (1) development of PCR-based co-dominant markers for nodulin genes, (2) mapping of nodulation mutants relative to candidate genes (e.g. ethylene perception loci of Arabidopsis), and (3) construction and characterization of a Medicago truncatula BAC library. One strategy to accelerate map-based cloning efforts in Medicago truncatula is to exploit the expected syntenic relationship with Medicago sativa (alfalfa), where a detailed genetic map is already available. Therefore a mapping population of >100 F₃ families is being analyzed as a cooperative effort between the US and Hungarian groups to determine the extent of synteny between M. truncatula and M. sativa. Supported by USDA (9704014) and NSF (9507535).