The species-rich and widespread genusTaraxacumF. H. Wiggers, 1780 (Asteraceae subfamily Cichorioideae) is one of the most taxonomically complex plant genera in the world, mainly due to its combination of different sexual and asexual reproduction strategies. Polyploidy is usually confined to apomictic microspecies, varying from 3x to 6x (rarely 10x). In this study, we focused on Taraxacum sect.Taraxacum(= T.sect.Ruderalia;T.officinalegroup), i.e., the largest group within the genus. We counted chromosome numbers and measured the DNA content for species sampled in Central Europe, mainly in Czechia. The chromosome number of the 28 species (T.aberransHagendijk, Soest & Zevenbergen, 1974,T.atrovirideŠtěpánek & Trávníček, 2008,T.atroxKirschner & Štěpánek, 1997,T.baeckiiformeSahlin, 1971,T.chrysophaenumRailonsala, 1957,T.coartatumG.E. Haglund, 1942,T.corynodesG.E. Haglund, 1943,T.crassumH. Øllgaard & Trávníček, 2003,T.deltoidifronsH. Øllgaard, 2003,T.diastematicumMarklund, 1940,T.gesticulansH. Øllgaard, 1978,T.glossodonSonck & H. Øllgaard, 1999,T.guttigestansH. Øllgaard in Kirschner & Štěpánek, 1992,T.huelphersianumG.E. Haglund, 1935,T.ingensPalmgren, 1910,T.jugiferumH. Øllgaard, 2003,T.laticordatumMarklund, 1938,T.lojoenseH. Lindberg, 1944 (=T.debrayiHagendijk, Soest & Zevenbergen, 1972,T.lippertianumSahlin, 1979),T.lucidifronsTrávníček, ineditus,T.obtusifronsMarklund, 1938,T.ochrochlorumG.E. Haglund, 1942,T.ohlseniiG.E. Haglund, 1936,T.perdubiumTrávníček, ineditus,T.praestabileRailonsala, 1962,T.sepulcrilobumTrávníček, ineditus,T.sertatumKirschner, H. Øllgaard & Štěpánek, 1997,T.subhuelphersianumM.P. Christiansen, 1971,T.valensMarklund, 1938) is 2n = 3x = 24. The DNA content ranged from 2C = 2.60 pg (T.atrox) to 2C = 2.86 pg (T.perdubium), with an average value of 2C = 2.72 pg. Chromosome numbers are reported for the first time for 26 species (all butT.diastematicumandT.obtusifrons), and genome size estimates for 26 species are now published for the first time.
