Nucleolus Organising Chromosomes in Brassica and Their Bearing on the Phylogeny of the Genus

Abstract

A numerical correspondence is seen in the number of nucleolus organising chromosomes in the 4 diploid Brassica species referred in the text. Based on the numerical correspondence the allopolyploid nature of not only of B. juncea var. gracilis (n=18) and B. napus var. oleifera (n=19) but also of the three genomes ‘a’, ‘b’ and ‘c’ has been suggested. The probable origin of the nucleolus organising chromosome of ‘b’ and ‘c’ genomes from that of ‘a’ genome through a reciprocal translocation has also been suggested.