In the process of constructing a detailed genetic map of rice using two cultivars, Nipponbare and Kasalath, 79 DNA probes (approximately 6.1 o/o of total DNA markers) showed two or more RFLP bands in Southern hybridization and were mapped at duplicate or triplicate loci over the 12 chromosomes. Thirty-three DNA probes were mapped in the distal regions of rice chromosomes 11 and 12. Thirteen among 33 DNA probes were detected at duplicate loci. Linkage alignment of these 13 markers on both chromosomes agreed perfectly within a distance of ca. 12 CM from the distal ends of chrounosomes 11 and 12. However, the other 20 DNA probes were mapped only on either chromosome 11 or chromosome 12, because the other bands were monomorphic between Nipponbare and Kasalath. These results indicate that the regions on rice chromosomes 11 an 12 are highly conserved as a duplicated chromosomal segment. Such highly conserved segments were not found anywhere else in the other chromosomes in our map.
Japanese Society of Breeding