TOWARDS AN INTEGRATION OF THE PHYSICAL AND THE GENETIC CHROMOSOME MAPS OF BARLEY BY IN-SITU HYBRIDIZATION

The relationship between physical and genetic distances on the barley chromosomes was studied by fluorescence in situ hybridization (FISH). Physical mapping of low- and single copy genes by FISH includes the pr otein Zx gene on chromosome 4 (4I), the alpha-amylase, high pI, genes on chromosome 6 (6I), the early-methionine-labelled polypeptide gene(s ) on chromosome 5 (1I), and the leaf thionin genes on chromosome 6 (6I ). Two interstitial sites of the telomere-associated sequence, the HvR T-family, were mapped by FISH on chromosome 3 (3I), and hybridization sites of histone 4 and ubiquitin genes were detected on chromosomes 1 (7I) and 5 (1I), respectively. In addition, a 5SrDNA locus was mapped genetically on chromosome 1. The study provides seven new anchor sites for integrating the genetic and physical chromosome maps and allows e stimation of the relationship between physical and genetic distances t o 1-2 Mb/cM for the distal 40% of the chromosome arms. All chromosome arms studied showed a strongly reduced level of recombination in their inner halves. These results are discussed in relation to the feasibil ity of map-based cloning in barley and other cereal species.