Mapping and organization of highly-repeated DNA sequences by means of simultaneous and sequential FISH and C-banding in 6x-triticale

Three families of highly repeated sequences from rye and the rRNA multigenes (NOR and 5S) have been mapped by FISH and C-banding, in chromosomes of triticale. The psc119.2 probe showed interstitial hybridization in chromosome arms 1RS, 1RL, 4RL, 5RL, 6RS, 6RL, 7RS and 7RL, and is very effective for chromosome identification of rye chromosomes in triticale. This sequence also hybridizes to the 4A, 5A and the seven B-genome wheat chromosomes. Simultaneous hybridization with the psc119.2 and pTa794 (5S rRNA) is very useful to distinguish the metacentric chromosomes 2R and 3R. The pSc74 probe appears at interstitial sites in the long arm of the most heterobrachial chromosomes (5R and 6R). The three repetitive sequences of 120 bp, 480 bp, and 610 bp hybridize to telomeric regions in rye chromosomes. Different arrangements and complex organizations consisting of arrays of three or more family sequences were found. The results demonstrate a great variation in the relative arrangement of the repetitive sequences in the telomeres of the rye chromosomes. There were quantitative differences in each cytological marker between triticale lines in both in situ labelling and C-banding, probably as the result of differences in the number and/or kind of repeat sequence.