Variability in giant fennel ( Ferula communis, Umbelliferae ): Ribosomal RNA nuclear genes

The rDNA of five accessions of the giant fennel (Ferula communis, Umbelliferae) was analyzed. The restriction map of Bam H 1, Eco R 1 and Hind III sites was established for one of them. Variation between the five accessions was observed at several levels. Three have a homogeneous repeat size, whereas the two others are heterogeneous, one presenting an additional site heterogeneity. However, the general pattern of organization is very similar and there is much greater similarity between theFerula accessions than with the pattern observed for carrot, a plant from the same family. Variation was also observed in the copy number of the rDNA repeats, which ranges from ≃ 900 to 3 500. The results demonstrate that the five accessions can be clearly differentiated by molecular analysis of their DNA although they belong to the same species or subspecies. They also demonstrate that different isolated populations of a species evolve independently, thus shedding light on the molecular mechanisms of speciation.