Substantial Genome Size Variation in Taraxacum stenocephalum (Asteraceae, Lactuceae)

Abstract

There are only a few exceptions to the rule that polyploidy in Taraxacum is associated with agamospermy. One of them is the sexual, tetraploid species Taraxacum stenocephalum. Incidentally, remarkable variation in karyology was found in this species. The present study aims to confirm this variation by an extensive screen of nuclear DNA content. Individuals from two large populations in the Lesser and Greater Caucasus, Georgia were analyzed using flow cytometry to ascertain intraspecific nuclear DNA content variation. Across the whole data set comprising all 159 individuals, a 1.223-fold difference was detected based on propidium iodide (PI) analyses. To verify this finding, we compared flow-cytometric data obtained using DAPI (4′,6-diamidino-2-phenylindole) and PI staining using a representative subset of individuals. This comparison revealed a 1.194-fold difference in DNA content for DAPI and a 1.219-fold difference for PI. Mean nuclear genome size in absolute terms (2C value ± s.d.) was estimated at 4.38 ± 0.21 pg, ranging from 4.01 pg to 4.89 pg, despite the invariable chromosome counts of 2n = 32. A regression analysis comparing the datasets for DAPI and PI staining found a strong correlation between data obtained by the DAPI and PI dyes (R = 0.976; P = 0.0001). Simultaneous high-resolution flow-cytometric analyses also proved the accuracy of our findings. We discuss possible sources of these large differences in DNA content within Taraxacum stenocephalum. Further research is needed to identify the source of this remarkable variation.

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Acknowledgments

We wish to thank George Nakhutsrishvili, Otar Abdaladze and other staff of the Institute of Botany of the Georgian Academy of Science, who were instrumental to the success of the expedition, and Eva Ibermajerová who helped with plant cultivation. This project was financially supported by the Czech Science Foundation (206/05/0970) and partly by the Research Plan of the Institute of Botany, Academy of Sciences of the Czech Republic (AV0Z60050516), the Research Plan of the Faculty of Science, Charles University in Prague (MSM 0021620828) and another grant from the Czech Science Foundation (206/08/H049).

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Correspondence to Pavel Trávníček.

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Trávníček, P., Kirschner, J., Chudáčková, H. et al. Substantial Genome Size Variation in Taraxacum stenocephalum (Asteraceae, Lactuceae). Folia Geobot 48, 271–284 (2013). https://doi.org/10.1007/s12224-013-9151-7

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Keywords

  • Flow cytometry
  • Genome size
  • Intraspecific DNA content variation
  • Taraxacum stenocephalum