Molecular characterization and chromosomal distribution of species-specific repetitive DNA sequences from Beta corolliflora, a wild relative of sugarbeet

Repetitive DNA sequences have been isolated from a Sau3AI plasmid library o f tetraploid Beta corolliflora (2n = 4x = 36), a wild relative of sugar bee t (B. vulgaris). The library was screened by differential hybridization wit h genomic DNA of B. corolliflora and B. vulgaris. When used as probes for S outhern hybridization of genomic DNA, six clones were determined to represe nt highly repetitive DNA families present only in the B. corolliflora genom e. Five other sequences were highly repetitive in B. corolliflora and low o r single copy in B. vulgaris. The insert size varied between 43 bp and 448 bp. Two sequences pBC1279 and pBC1944 displayed strong homology to a previo usly cloned satellite DNA from B. nana. With one exception, sequences are t andemly arranged as revealed by a typical ladder pattern after genomic Sout hern hybridization. The chromosomal distribution of five probes was determi ned by fluorescence in situ hybridization (FISH) of mitotic metaphases from B. corolliflora and a triploid hybrid between B. vulgaris and B. corollifl ora. Three sequences were spread along all chromosome arms of B. corolliflo ra while one sequence was present on only six chromosomes. The chromosome-s pecific sequence pBC216 was found in close vicinity to the 5S rDNA located on B. corolliflora chromosome IV. This set of species-specific sequences ha s the potential to be used as probes for the identification of monosomic al ien addition lines and for marker-assisted gene transfer from wild beet to cultivated beet.