We assessed the genetic differentiation of the Mediterranean olive from its wild relatives found in different geographic areas (Mediterranean, Asia, Africa) using eighty RAPDs revealed with eight primers. Variance analysis (AMOVA) enabled us to estimate the overall genetic differentiation parameters between wild populations. Oleasters from the Near East and Turkey were discriminated from the other Mediterranean populations. Olea laperrinei, O. maroccana and O. cerasiformis were the taxa the most related to the Mediterranean olive. In contrast, O. africana was shown to be the most genetically distant taxa from the Mediterranean olive. However, we characterised hybrid trees between these two taxa. Significant trends between genetic and geographic distances were met within the subspecies cuspidata and within the Mediterranean olive. A genetic diversity gradient was observed in both subspecies europaea and cuspidata. These results are in agreement with a mechanism of differentiation by distance in the O. europaea complex, but another non-exclusive mechanism could also be gene flow between differentiated taxa. Furthermore, we characterised the discriminating power of each RAPD to recognise the different taxa using intraclass correlation coefficients. Lastly, IGS-RFLPs enabled us to assess rDNA polymorphisms on a sub-sample of individuals. On the basis of these data, a low interspecifc differentiation was found. This suggests a recent genetic divergence between the different taxa of the O. europaea complex or the occurrence of gene flow during favourable periods or because human displacements. All the olive cultivars were genetically related to the oleaster populations supporting that Mediterranean is the olive domestication area.

Ribosomal DNA polymorphisms were studied in 6 lines of Petunia hybrida using EcoRI, BamHI, HindIII, KpnI, Sad or XhoI. Each line carries several unit types, and 13 types were found in lines, which was not expected. We characterized the unit types and we determined the number of loci. Two kinds of unit types carrying no or several HindIII sites were revealed. The longest EcoRI and BamHI fragments in St43 correspond to a 11.4 kb unit type. Moreover, a 2.6 kb EcoRI fragment cannot be mapped in the 11.4 kb unit. It was found to be equivalent to the 2.45 kb EcoRI fragment carrying the 25 S rRNA coding sequence. Consequently, it was mapped in another unit 11.7 kb long. In Tlh1 the corresponding EcoRI and BamHI fragments enabled us to construct 8.8, 9.2 and 10.8 kb segments. These fragments are therefore considered to be part of the 11.4 kb unit length. Other lines display combinations of these length units. The inheritance of polymorphic fragments of lines (St43 and Tlh1) for 50 individuals of the 2 possible backcrosses [(St43 x Tlh1) x St43] and [(St43 x Tlh1) x Tlh1] indicated at least 2 loci. The presence in Sk176 of 6.2, 5.7 and 5.4 EcoRI fragments suggested 3 loci. The haploid plants obtained from the hybrid (St43 x Tlh1) display 1 individual carrying the 3 unit types present in the hybrid which proves the presence of 3 rDNA loci in Tlh1. Moreover, the segregation in the backcrosses corresponds to only 2 loci in St43. It carries a nulli-allele. Evidence for such hypotheses were obtained by in situ hybridization with a biotinylated probe. The Tlh1 and Tlh7 dihaploid lines display more unit types and, consequently, more polymorphisms than other lines.