PHYSICAL MAPPING OF SINGLE-COPY SEQUENCES IN Beta SPECIES

Institute of Crop Science and Plant Breeding, Christian-Albrecht University of Kiel, Olshausenstr.40, D-24118 Kiel, Germany

Sugar beet (Beta vulgaris L., 2n=18) is highly susceptible to the beet cyst nematode (Heterodera schachtiiSchm.) which causes severe loss of yield. By interspecific crossings resistance genes originating from the wild beet Beta procumbens have been transferred to sugar beet. Nematode resistant monosomic addition lines (2n=18+1) containing a wild beet chromosome or chromosome fragment and a diploid homozygous sugar beet line (2n=18) which carry a translocation from the wild beet chromosome were investigated by fluorescence in situ hybridization (FISH). Alien chromatin was differentiated from the sugar beet background by genomic in situ hybridization (GISH) using genomic DNA from B. procumbens as probe. Yeast artifical chromosomes (YACs) were localized by double-target in situ hybridization and enabled the detection of the wild beet translocation and the orientation of a contig spanning the introgression. For detailed cytogenetic analysis of the translocation the nematode resistant gene Hs1^pro-1 was physically mapped. An internal gene sequence containing 684bp was detected on the translocation line, the monosomic addition line and the wild beet B. procumbens demonstrating that translocation originated from terminal recombination of a wild beet chromosome.