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Genome Size Study in the Valerianaceae: First Results and New Hypotheses

DOI: 10.1155/2010/797246

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The purpose of this study is to provide a new focus to contribute, from the perspective of genomic evolution, towards a better understanding of the Valerianaceae evolutionary history. Chromosome numbers were determined by Feulgen staining in 24 populations of 18 species (first count for Valerianella multidentata, –16), and DNA contents were assessed by flow cytometry in 74 populations of 35 species (first assessments in all taxa but Centranthus ruber). A molecular phylogeny based on the trnL-trnF and including 41 new sequences was established, with the first DNA sequence for Centranthus nevadensis, Valeriana rotundifolia, V. saxatilis, Valerianella multidentata, and V. turgida. This work is the first large genome size study devoted to the Valerianaceae, showing a range of DNA amounts from ?pg (Valerianella turgida) to ?pg (Valeriana officinalis). At the family level, changes in basic chromosome number and genome size coincide with or precede major shifts in the evolutionary history of the group, such as those concerning stamen number and floral symmetry. 1. Introduction The family Valerianaceae (currently considered within the Caprifoliaceae s.l.; [1]) comprises ca. 400 species of which approximately 200 are included in Valeriana L., the biggest genus of the order Dipsacales. The Valerianaceae are cosmopolitan in their natural distribution, with the exceptions of Australia and the Pacific islands, where they were introduced, and can be nowadays considered as naturalized. Several of their representatives have economic interest as medicinal (e.g., V. officinalis L.), edible (e.g., Valerianella Mill., corn salad or lamb’s lettuce), or ornamental plants (e.g., Centranthus DC.). The family always roused important scientific interest, and its study has broadly benefited from the new molecular techniques, especially the phylogenetic reconstructions. Recent phylogenies based on DNA sequencing [2–7] have considerably modified the traditional classification of the family [8–12]. Molecular results recognize only six genera: Centranthus, Fedia Gaertn., Nardostachys DC., Patrinia Juss., Valeriana (including Aretiastrum DC., Astrephia Dufr., Belonanthus Graebn., Phyllactis Pers., Porteria Hook., and Stangea Graebn.), and Valerianella. Plectritis (Lindl.) DC. is nested amongst South American Valeriana [5, 6]. Moreover, Bell [7] suggested a possible further taxonomic treatment of the family considering Fedia as a synonym of Valerianella. New genera may also be described for some of the Valeriana species that do not group with their congenerics in the phylogenetic

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