Physical Mapping of 5S and 45S rDNA Sequences by FISH in Species of the Genus Iris L.

For the first time, FISH was used to map 5S and 45S rDNA sequences in two species of the genus Iris L. Ten major 45S rDNA sites were detected on chromosomes and interphase nuclei of Iris pumila L. and six sites in Iris pseudopumila Tineo; 12 loci 5S rDNA were found in I. pumila, while only two were in I. pseudopumila. A high level of aneuploidy (60–80%) was revealed in I. pumila plants, which is probably associated with the hybrid origin of the species. Given the obtained results, it is quite probable that I. pseudopumila may be one of the parental forms of the allotetraploid I. pumila. The obtained data are the basis for further evolutionary studies of this species. The evolutionary changes of diploid ancestral forms following the formation of allopolyploids and the importance of ribosomal DNA sequences in detecting these changes are discussed.