Molecular cytogenetic localization and characterization of 5S and 25S rDNAloci for chromosome identification in oilseed rape (Brassica napus L.)

Chromosome identification in oilseed rape (Brassica napus L.) is extremely difficult using conventional cytogenetic techniques because amphidiploid Br assica species possess numerous very small chromosomes with few cytogenetic landmarks. In combination with methods for improved chromosome preparation s, we used a simplified fluorescence in situ hybridization (FISH) technique to localize simultaneously the gene families coding for 5S and 25S rDNA in B. napus. The resulting hybridization patterns enabled ten of the 19 oilse ed rape chromosome pairs to be unequivocally identified. (C) 2000 Annals of Botany Company.