CHARACTERIZATION OF HETEROCHROMATIC REGIONS IN TROVITA ORANGE (CITRUS-SINENSIS OSBECK) CHROMOSOMES BY THE FLUORESCENT STAINING AND FISH METHODS

CMA/DAPI double staining and FISH methods using rDNA and telomere spec ific repeated sequences as probes were applied to characterize the lar ge amount of heterochromatin in the telomeric regions of 'Trovita' ora nge (Cirrus sinensis Osbeck) chromosomes. As a result, all the heteroc hromatic regions were CMA+/DAPI-, and thus were GC rich. Three CMA+/DA PI- heterochromatic regions were positive to the 26S rDNA probe. Telom ere arrays consisting of T-m(A)G(n) were detected on the extreme ends of each chromosome and most of the CMA+/DAPI- heterochromatic regions were ordered close inside the telomere specific repeated sequences. Th e data obtained in this study will be useful for karyotyping, systemat ics, and molecular analysis of orange chromosomes.