Chloroplast DNA variation in the cultivated and wild olive taxa of the genus Olea L.

Polymorphism in the lengths of restriction fragments of the whole cpDNA mol ecule were studied in 15 taxa (species or subspecies) of the genus Olea. Fr om restriction analysis using nine endonucleases, 28 site mutations and fiv e length polymorphisms were identified, corresponding to 12 distinct chloro types. From a phenetic analysis based on a Nei's dissimilarity matrix and a Dollo parsimony cladistic analysis using, as an outgroup, a species of the genus Phillyrea close to Olea, the ten taxa of section Olea were distingui shed clearly from the five taxa of section Ligustroides which appear to pos ses more ancestral cpDNA variants. Within the section Ligustroides, the tro pical species from central-western Africa, Olea hochtetteri, showed a chlor otype which differed substantially from those of the other four Olea taxa g rowing in southern Africa, supporting a previous assessment according to wh ich O. hochtetteri may have been subjected to a long period of geographical isolation from the other Olea taxa. Within the Olea section, three phyla w ere identified corresponding to South and East Africa taxa, Asiatic taxa, a nd a group including Saharan, Macaronesian and Mediteranean taxa, respectiv ely. On the basis of cpDNA variation, the closest Olea taxa to the single M editerranean species, Olea europaea, represented by its very predominant ch lorotype, observed in both wild and cultivated olive, were found to be Olea laperrinei (from the Sahara), Olea maroccana (from Maroccan High Atlas) an d Olea cerasiformis (from Macaronesia). These three taxa, which all share t he same chlorotype, may have a common maternal origin.