Aim  The oleaster is believed to have originated in the eastern Mediterranean, implying that those in the western Mediterranean basin could be feral. Several studies with different molecular markers (isozymes, random amplified polymorphic DNA, amplified fragment length polymorphism) have shown a cline between the eastern and the western populations, which supports this hypothesis. To reconstruct the post‐glacial colonization history and establish a relationship between olive and oleaster populations in the Mediterranean basin, analyses were carried out on the genetic variation of chloroplast DNA (chlorotype) and at 12 unlinked simple sequence repeat (SSR) loci, sampling a total of 20 oleaster groves. Location  This is the first known large‐scale molecular study of SSR loci based on samples of both oleasters and cultivars from the entire Mediterranean basin. Methods  Samples were taken from 166 oleasters in 20 groves of modern populations, and 40 cultivars to represent molecular diversity in the cultivated olive. The Bayesian method and admixture analysis were used to construct the ancestral populations (RPOP; reconstructed panmictic oleaster populations) and to estimate the proportion of each RPOP in each tree. If one tree can be assigned to two or more RPOPs, it can be regarded as a product of hybridization between trees from different populations (i.e. admix origin). Results  On this first examination of the SSR genetic diversity in the olive and oleaster, it was found to be structured in seven RPOPs in both eastern and western populations. Based on different population genetic methods, it was shown that: (1) oleasters are equally present in the eastern and the western Mediterranean, (2) are native, and (3) are not derived from cultivars. Chlorotypes (one and three in the eastern and western Mediterranean, respectively) revealed fruit displacement for the oleasters. Main conclusions  Oleaster genetic diversity is divided into seven regions that could overlay glacial refuges. The gradient, or cline, of genetic diversity revealed by chloroplast and SSR molecular markers was explained by oleaster recolonization of the Mediterranean basin from refuges after the last glacial event, located in both eastern and western regions. It is likely that gene flow has occurred in oleasters mediated by cultivars spread by human migration or through trade. Animals may have helped spread oleasters locally, but humans have probably transported olives but not oleaster fruits over long distances. We found that cultivars may have originated in several RPOPs, and thus, some may have a more complex origin than expected initially.

Wood formation is a complex biological process, involving five major developmental steps, including (1) cell division from a secondary meristem called the vascular cambium, (2) cell expansion (cell elongation and radial enlargement), (3) secondary cell wall deposition, (4) programmed cell death, and (5) heartwood formation. Thanks to the development of genomic studies in woody species, as well as genetic engineering, recent progress has been made in the understanding of the molecular mechanisms underlying wood formation. In this review, we will focus on two different aspects, the lignification process and the control of microfibril angle in the cell wall of wood fibres, as they are both key features of wood material properties.

One hundred and thirteen olive (Olea europaea L.) accessions were characterized using randomly amplified polymorphic DNA (RAPD) markers. Forty-five polymorphic RAPD markers were obtained enabling us to distinguish 102 different RAPD profiles. The approximate estimation of the probability of obtaining the same RAPD profile for two different trees was between 6.75 × 10-5 and 4.82 × 10-14. A dendrogram was constructed using Ward's minimum variance algorithm based on chi-square distances. This led to a more clear-cut classification of profiles than the classical approach of unweighted pair group method with arithmetic average. Twenty-four clusters of RAPD profiles were shown in Ward's dendrogram. Reliability of the dendrogram structure was checked using variance analysis. RAPD data exhibited an acceptable resolving power for cultivar identification. A combination of three primers was proposed for rapid molecular identification of cultivars in collections and in nurseries.

RAPD profiles of 121 olive cultivars were compared to those of 20 natural oleaster populations from eastern and western parts of the Mediterranean Basin. Considering the proximi ties of RAPD profiles between cultivars and eastern or western oleaster populations, clear differences appeared between groups of cultivars. Cultivars from Israel, Turkey, Syria, Greece and Sicily were, with very few exceptions, close to the eastern group of oleasters; in contrast, clones from Continental Italy, Continental France, Corsica, Spain and the Maghreb were closer to the western group. This genetic structure is coherent with a local selection of cultivars all around the Mediterranean Basin. The cultivars were also characterised for their mitochondrial cytotype. This information led to the conclusion that a great majority (103 of 121) of the cultivars originated by maternal descent from the eastern populations as they carry the mitotypes ME1 or ME2. However, the selection process, which involved hybridisation by pollen from local populations, could have led to an RAPD profile closer to western than to eastern natural populations. Furthermore, the other cult ivars with the western mitotypes MOM or MCK generally kept a nuclear RAPD profile close to the profile of western natural populations. Consequently, they could result from exclusively local material (as for Corsica). Cultivars displaying such mitotypes could also have been selected in hybrids or introgressed genotypes between western local oleasters and the introduced eastern varieties used as male parents, restoring an eastern RAPD type. Therefore, the process of olive domestication appeared as disymmetrical: the western Mediterranean is probably a zone where olive trees from the East, once introduced, have been hybridised and back-crossed with the indigenous olives.

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