Nuclear DNA content variation within the genus Taraxacum (Asteraceae)

Nuclear DNA content was estimated using flow cytometry in 13 sections represented by 18 species of the genus Taraxacum using propidium iodide as the DNA stain. Investigated plants represented diploid, triploid and tetraploid species from sections considered both primitive and advanced, i.e., T. sect. Dioszegia, Piesis, Glacialia, Mongolica, Scariosa, Obovata, T. pyrenaicum group, T. sect. Coronata, Palustria, Taraxacum (= Crocea), Kashmirana, Ruderalia and Erythrosperma. Estimated nuclear 2C DNA content ranged from 1.74 pg in diploid T. linearisquameum (T. sect. Ruderalia) to 6.91 pg in tetraploid T. albidum (T. sect. Mongolica), demonstrating 3.97-fold variation. The lowest monoploid genome size 1C(x) = 0.87 pg was recorded in T. linearisquameum (T. sect. Ruderalia) together with T. brachyglossum (T. sect. Erythrosperma), and the highest one (1.73 pg) was recorded in T. albidum (T. sect. Mongolica), giving a 1.99-fold difference in the genus. No significant differences in genome size were observed within T. sect. Ruderalia, similarly no intraspecific variation was observed in T. paludosum (T. sect. Palustria) and T. serotinum (T. sect. Dioszegia). These results indicate a high intraspecific stability of the trait. Preliminary comparisons of genome size in species/sections considered to be close relatives were made. These data give tentative additional evidence for the close phylogenetic relationship between sections Palustria and Piesis and against the close relationship between sections Piesis and Dioszegia.