Karyoptype analysis of Daucus carota L. using Giemsa C-banding and FISH of 5S and 18S/25S rRNA specific genes

In Daucus carota L. subsp. sativus (Hoffm.) Arc. sixteen ideally extended mitotic pro-metaphases with total genomic length variation of 9% were used for karyotype analysis after Giemsa C-banding. The C-bands were localized exclusively in centromeric positions of all chromosome types (D1 - D9). After computer-aided measurements of the chromosomes with respect to their length and arm ratios the karyotype could be subdivided into two groups: one with five longer subtelocentric chromosome pairs (including the satellite chromosome pair) and one with four shorter submetacentric chromosome pairs. A t-test confirmed that most of the arm length differences between the chromosomes of the same group were significant, except for the short arms within the subtelocentric group and the very similar short arms of D5 and D8 in the submetacentric group. Using fluorescence in situ hybridization the physical localization of rRNA genes was studied. The 18S/25S rRNA gene locus was found on the short arm of the longest subtelocentric satellite chromosome D1 and the 5S rRNA locus on the longer arm of the submetacentric chromosome D5. Based on statistical analysis of 16 pro-metaphases all nine chromosome pairs of the carrot karyotype were distinguishable.