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Folia Geobotanica

, 44:423 | Cite as

Karyological Observations in Medicago Section Dendrotelis (Fabaceae)

  • Marcela Rosato
  • Josep A. Rosselló
Article

Abstract

Medicago section Dendrotelis comprises polyploid, woody shrubs restricted to rocky and cliff faces in coastal places of the Mediterranean basin, showing a very close morphology. This has resulted in controversial taxonomic studies, differing in the circumscription and number of recognized species (from one to three). In the present study, cytogenetic studies (meiotic analysis, C-banding, Ag-NOR banding) were made in M. arborea, M. strasseri, and M. citrina to determine their karyological and evolutionary relationships. The observation of meiocytes revealed a regular meiotic cycle in all species. At pachytene stage, chromosomes showed constitutive heterochromatic blocks (knobs) that were species-specific, and clearly discriminate M. arborea and M. strasseri from M. citrina. Conventional karyotypes of M. strasseri and M. arborea were similar concerning chromosome classes, the apparent chromosome length, and the morphology of the single NOR chromosome pair. However, C-banding technique revealed karyotypic differences between both species. In contrast, M. citrina exhibited a slightly asymmetric karyotype, the presence of two pairs of chromosomes showing secondary constrictions, a similar apparent chromosome length, and two pairs of active rDNA loci. Its C-banded karyotype strikingly differed from those observed in M. arborea and M. strasseri, and only three chromosome pairs showed heterochromatic blocks. These cytogenetic data indicate a clear evolutionary split in woody medics (tetraploid vs hexaploid species), reflecting divergent patterns of karyological evolution. Taken together, all karyological data unequivocally support the recognition of M. citrina as a distinct species.

Keywords

Giemsa C-banding Mediterranean flora Nucleolar organizer region Polyploidy 

Notes

Acknowledgements

Several accessions of M. citrina were kindly provided by N. Torres and E. Laguna. We acknowledge M. Chiavarino and G. Nieto-Feliner for discussions and ideas shared during the work that improved the manuscript. This work has been partially funded by the CGL2007-60550/BOS project.

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Copyright information

© Institute of Botany, Academy of Sciences of the Czech Republic 2009

Authors and Affiliations

  1. 1.Jardí BotànicUniversidad de ValenciaValenciaSpain
  2. 2.Marimurtra Botanical GardenBlanesSpain

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