A monophyletic origin of the B chromosomes ofBrachycome dichromosomatica (Asteraceae) |
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| Authors: | Andreas Houben Nicole Thompson Richard Ahne Carolyn R Leach Dawn Verlin Jeremy N Timmis |
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| Institution: | (1) Department of Genetics, The University of Adelaide, 5005, South Australia, Australia;(2) Department of Crop Protection, The University of Adelaide, Waite Campus, PMB1, 5064 Glen Osmond, South Australia, Australia;(3) Bundesanstalt für Züchtungsforschung an Kulturpflanzen, D-06484 Quedlinburg, Germany |
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| Abstract: | The A and B chromosomes of different karyotype variants (cytodemes A1, A2, A3 and A4) ofBrachycome dichromosomatica were analysed by computer-aided chromosome image analysis and fluorescencein situ hybridisation (FISH). Ribosomal DNA and the B chromosome-specific sequence Bd49 were detected on all B chromosomes. In addition to minor size variation of the Bs, polymorphism of the rDNA and Bd49 position and copy number revealed two major types of B chromosomes. The B chromosomes of all the cytodemes were indistinguishable from each other in length, but that of A3 showed evidence of rearrangements consistent with its long-term geographic isolation. The results presented suggest a monophyletic origin of the B chromosomes ofB. dichromosomatica. |
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| Keywords: | Asteraceae Brachycome B chromosome polymorphism evolution karyotyping centromere |
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