VARIATION IN HIGHLY REPETITIVE DNA-COMPOSITION OF HETEROCHROMATIN IN RYE STUDIED BY FLUORESCENCE IN-SITU HYBRIDIZATION

The molecular characterization of heterochromatin in six lines of rye has been performed using fluorescence in situ hybridization (FISH). Th e highly repetitive rye DNA sequences pSc119.2, pSc74, and pSc34, and the probes pTa71 and pSc794 containing the 25S-5.8S-18S rDNA (NOR) and the 5S rDNA multigene families, respectively, were used. This allowed the individual identification of all seven rye chromosomes and most c hromosome arms in all lines. All varieties showed similar but not iden tical patterns. A standard in situ hybridization map was constructed f ollowing the nomenclature system recommended for C-bands. All FISH sit es observed appeared to correspond well with C-band locations, but not all C-banding sites coincided with hybridization sites of the repetit ive DNA probes used. Quantitative and qualitative differences between different varieties were found for in situ hybridization response at c orresponding sites. Variation between plants and even between homologo us chromosomes of the same plant was found in open-pollinated lines. I n inbred lines, the in situ pattern of the homologues was practically identical and no variation between plants was detected. The observed q uantitative and qualitative differences are consistent with a correspo nding variation for C-bands detected both within and between cultivars .