Cytotaxonomy of diploid and polyploid Aristolochia (Aristolochiaceae) species based on the distribution of CMA/DAPI bands and 5S and 45S rDNA sites
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Aristolochia is the largest genus of the family Aristolochiaceae and the only one with large chromosome number variation. A combination of fluorochrome banding and in situ hybridization of 5S and 45S rDNA probes was used to evaluate the structural karyotype variability of representatives of two subgenera: Siphisia, which seems to have a single chromosome number (2n = 32), probably derived from an old polyploidization event, and Aristolochia, including the Old World section Diplolobus and the New World Gymnolobus. Based on chromosome morphology and on the degree of diploidization of rDNA sites, A. serpentaria (Siphisia) was identified as an old hexaploid, whereas A. paucinervis (Diplolobus) seemed to be a recent hexaploid (2n = 34). The karyotypes of the five analyzed species of section Gymnolobus were structurally more stable than those from Diplolobus, which varied considerably in the type of heterochromatin, chromosome number, and morphology. These data indicate that fluorochrome banding and rDNA localization may substantially improve the cytotaxonomical analysis of this genus.
KeywordsAristolochia Cytotaxonomy Heterochromatin rDNA
The authors wish to thank Conselho Nacional de Desenvolvimento Científico e Tecnológico (Brazil), Fundação de Amparo à Ciência e Tecnologia de Pernambuco (Brazil), and Ministerio de Ciencia e Innovación (Spain) for their financial support, and to Dr. Leonardo Felix, Dr. Juliano Cabral, and Dr. Santiago Castroviejo for their kind help in collecting the plant material.
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