COMPARATIVE LINKAGE MAPS OF THE RICE AND MAIZE GENOMES

Genetic linkage maps have been constructed for the rice and maize geno mes on the basis of orthologous loci detected with a common set of cDN A clones. Conserved linkage groups could be identified, which together account for more than two-thirds of both genomes. In some instances, entire chromosomes or chromosome arms are nearly identical with respec t to gene order and gene content. The results also reveal that most of the genes (>72%) duplicated during ancient polyploidization are still present in the maize genome in duplicate copy. The comparative maps o f rice and maize provide a basis for interpreting molecular, genetic, and breeding information between these two important species and estab lish a framework for ultimately connecting the genetics of all grass s pecies.