The clone pAS"C" is a sequence related to M13 phage minisatellite sequences isolated from bovine DNA. It contains TGG repeats, and related sequences are abundant in the Citrus genome. Fluorescent in situ hybridization (FISH) signals detected using this clone as a probe showed that the TGG repeat-related sequences are found on all the Citrus chromosomes, but are not found in Citrus-specific CMA+/DAPI- heterochromatic regions located at the extreme ends of each chromosome. These data suggest that the TGG-repeated sequences are evolutionarily conserved and that the CMA+/DAPI- heterochromatic regions were added to the chromosome ends at a recent stage in Citrus evolution.