Molecular cytogenetic analysis of recently evolvedTragopogon(Asteraceae) allopolyploids reveal a karyotype that is additive of the diploid progenitors

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Abstract
Tragopogon mirusandT. miscellus(both 2n= 4x= 24) are recent allotetraploids derived fromT. dubius×T. porrifoliusandT. dubius×T. pratensis(each 2n= 2x= 12), respectively. The genome sizes ofT. mirusare additive of those of its diploid parents, but at least some populations ofT. miscellushave undergone genome downsizing. To survey for genomic rearrangements in the allopolyploids, four repetitive sequences were physically mapped. TPRMBO (unit size 160 base pairs [bp]) and TGP7 (532 bp) are tandemly organized satellite sequences isolated fromT. pratensisandT. porrifolius, respectively. Fluorescent in situ hybridization to the diploids showed that TPRMBO is a predominantly centromeric repeat on all 12 chromosomes, while TGP7 is a subtelomeric sequence on most chromosome arms. The distribution of tandem repetitive DNA loci (TPRMBO, TGP7, 18S‐5.8S‐26S rDNA, and 5S rDNA) gave unique molecular karyotypes for the three diploid species, permitting the identification of the parental chromosomes in the polyploids. The location and number of these loci were inherited without apparent changes in the allotetraploids. There was no evidence for major genomic rearrangements inTragopogonallopolyploids that have arisen multiple times in North America within the last 80 yr.
Funding Information
  • NSF-NATO (DGE− 0000658)
  • Agency of the Czech Republic (204/01/0313, 521/01/0037)
  • Natural Environmental Research Council
  • US-UK Fulbright Distinguished Professorship Program
  • University of Florida Research Foundation