Karyotypes and Physical Mapping of Ribosomal DNA with Oligo-Probes in <i>Eranthis</i> sect. <i>Eranthis</i> (Ranunculaceae)

A comparative karyotype analysis of four species of yellow-flowered <i>Eranthis</i> sect. <i>Eranthis</i>, i.e., <i>E. bulgarica</i>, <i>E. cilicica</i>, <i>E. hyemalis</i>, and <i>E. longistipitata</i> from different areas, has been carried out for the first time. All the studied specimens had somatic chromosome number 2<i>n</i> = 16 with basic chromosome number <i>x</i> = 8. Karyotypes of the investigated plants included five pairs of metacentric chromosomes and three pairs of submetacentric/subtelocentric chromosomes. The chromosome sets of the investigated species differ mainly in the ratio of submetacentric/subtelocentric chromosomes, their relative lengths, and arm ratios. A new oligonucleotide probe was developed and tested to detect 45S rDNA clusters. Using this probe and an oligonucleotide probe to 5S rDNA, 45S and 5S rDNA clusters were localized for the first time on chromosomes of <i>E. cilicica</i>, <i>E. hyemalis</i>, and <i>E. longistipitata</i>. Major 45S rDNA clusters were identified on satellite chromosomes in all the species; in <i>E. cilicica</i>, minor clusters were also identified in the terminal regions of one metacentric chromosome pair. The number and distribution of 5S rDNA clusters is more specific. In <i>E. cilicica</i>, two major clusters were identified in the pericentromeric region of a pair of metacentric chromosomes. Two major clusters in the pericentromeric region of a pair of submetacentric chromosomes and two major clusters in the interstitial region of a pair of metacentric chromosomes were observed in <i>E. longistipitata</i>. <i>E. hyemalis</i> has many clusters of different sizes, localized mainly in the pericentromeric regions. Summarizing new data on the karyotype structure of <i>E.</i> sect. <i>Eranthis</i> and previously obtained data on <i>E.</i> sect. <i>Shibateranthis</i> allowed conclusions to be formed about the clear interspecific karyological differences of the genus <i>Eranthis</i>.