The primary goal of this research is to assemble a physical map of the Arabidopsis genome. Mapping will be achieved by linking the entire genome of Arabidopsis thaliana which will ultimately consist of a fully overlapping collection of clones encompassing the 5 linkage groups. The genome linking using YAC (yeast artificial chromosome) clones to contig hybridization is listed as the highest priority activity in the long-range plan for the Multinational Coordinated Arabidopsis Genome Research Project. The physical map will provide easy access to any region of the genome thereby simplifying the cloning of important loci which have been identified by mutational analysis. The probes used in this study will be placed in the national Arabidopsis resource center and will be made available to the general research community.