Olive domestication from structure of oleasters and cultivars using nuclear RAPDs and mitochondrial RFLPs

Abstract

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.

Construction of Core Collections Suitable for Association Mapping to Optimize Use of Mediterranean Olive (Olea europaea L.) Genetic Resources

“…By contrast, both core collections proposed in the current study accurately reflected the geographic distribution of cultivated olive, and demonstrated the high admixture level, since 48% and 52% of 50 and 94 entries, respectively, originated from the central Mediterranean zone. Our proposal is supported by the fact that the central Mediterranean zone is a hybrid area between the eastern and western zones, as shown by the admixed inferred ancestry of most of the genotypes sampled in this area [52], [96]. Strikingly, when comparing the varietal composition in the CC 94 core collection with those previously published for olive, we found that only 11 and 12 varieties were shared with those reported by Diez et al [66] and Belaj et al [51], respectively.…”

Genetic structure and core collection of the World Olive Germplasm Bank of Marrakech: towards the optimised management and use of Mediterranean olive genetic resources

“…As previously shown in Mediterranean wild and domesticated olives (Besnard et al 2002, 2007; Breton et al 2006), all eastern Mediterranean accessions carried E1, whereas lineages E2 and E3 were only observed in the western Mediterranean Basin, but with a relatively low frequency in cultivars (16%; Besnard et al 2001a). These cpDNA lineages again confirm that cultivated olive has been selected from different gene pools from both eastern and western regions of the Mediterranean Basin (Besnard et al 2001c). …”

Genetic diversity and gene flow between the wild olive (oleaster, Olea europaea L.) and the olive: several Plio‐Pleistocene refuge zones in the Mediterranean basin suggested by simple sequence repeats analysis

“…Domestication has been documented and previously reported by several authors (e.g. Zohary, 1994), with the assertion that cultivars moved westward with human migration supported by several authors (Besnard et al. , 2001a; Belaj et al.…”

“…, 1999) and random amplified polymorphic DNA (RAPD) (Fabbri et al. , 1995; Besnard et al. , 2001a) and recently with simple sequence repeat (SSR) analysis for cultivar identification (Cipriani et al.…”