A NEW METHOD FOR DIFFERENTIAL STRAINING OF BRASSICA METAPHASE CHROMOSOMES, AND KARYOTYPES OF BRASSICA-CAMPESTRIS, BRASSICA-OLERACEA, AND BRASSICA-NAPUS

Mitotic cells from three Brassica species, B. campestris L., B. olerac ea L., and B. napus L. have been differentially stained after cold tre atment and application of the ASG method for G-banding. Karyotypes and idiograms are presented. In all three species the chromosomes can be matched to individual pairs. The heterochromatic satellite next to the nucleolar organizer region (NOR) differs from the rest of the chromos omal material by having a very faint colour. It responds to the staini ng procedure in the same way as cold sensitive regions of chromatin de scribed in other species. In Brassica this type of reaction is apparen tly limited to the satellite next to the active NOR.