Dot-like micro B chromosomes of Brachycome dichromosomatica were analy
sed for their sequence composition. Southern hybridization patterns of
a total micro B probe to genomic DNA from plants with and without mic
ro Bs demonstrated that the micro Bs shared sequences with the A chrom
osomes. In addition to telomere, rDNA and common A and B chromosome se
quences, a new B-specific, highly methylated tandem repeat (Bdm29) was
detected. After in situ hybridization with Bdm29 the entire micro B c
hromosome was labelled and clustering of the condensed micro Bs could
be observed at interphase. A high number of Bdm29-like sequences were
also found in the larger B chromosomes of B. dichromosomatica and in o
ther Bs within the genus Brachycome.