Allozyme variation of oleaster populations (wild olive tree) (Olea europaea L.) in the Mediterranean Basin

Abstract

As a result of the early domestication and extensive cultivation of the olive tree throughout the Mediterranean Basin, the wild-looking forms of olive (oleasters) presently observed constitute a complex, potentially ranging from wild to feral forms. Allozyme variation was analysed at 10 loci in 31 large and 44 small oleaster populations distributed in various habitats of the Mediterranean Basin and in two populations of the wild subspecies Olea europaea subsp (ssp) guanchica, endemic to the Canary islands and closely related to oleasters. At eight polymorphic loci, 25 alleles were identified. Genetic evidence that nondomesticated oleasters still survive locally was provided by the occurrence of four and one alleles shared exclusively by the eight western and two eastern oleaster populations, respectively, which were collected in forests potentially containing genuinely wild forms according to environmental, historical and demographic criteria. As reported previously from cytoplasmic and RAPDs analysis, substantial genetic differentiation was observed between the eastern oleaster populations genetically close to most olive clones cultivated in the Mediterranean Basin, and the western populations that are related to the wild Canarian populations. In addition, the occurrence of significantly lower heterozygosity in cultivated olive than in oleasters, whatever their origin, suggests that intensive selection involving inbreeding has taken place under cultivation to obtain particular characteristics in the olive cultivars.

Microsatellite marker-based identification and genetic relationships of olive cultivars from the Extremadura region of Spain

“…Most of the alleles in cultivated accessions were common between local or foreign cultivars (16 and 8% of alleles were only detected in local and foreign cultivars, respectively). In the present study, allele identification detected evidence of the survival of indigenous wild oleasters, in agreement with previous research using allozymes (Lumaret et al, 2004) and molecular markers (Belaj et al, 2007;Erre et al, 2010). Nevertheless, as opposed to allele comparison, cultivated olive registered higher heterozygosity levels.…”

Genetic relationships among and within wild and cultivated olives based on RAPDs

“…Cultivated olives, on the other hand, are mostly produced through the vegetative method (Mendilcioglu, 1999). In this case, as Lumaret et al (2004) mentioned in their study, heterozygosity in wild olives is higher than in cultivated olives. Thus, it is expected that genetic similarities of wild and cultivated olives are distant.…”

On the origin of the invasive olives (Olea europaea L., Oleaceae)

“…The detection of three divergent Mediterranean ptDNA haplotypes clearly indicates that europaea populations originated from multiple individuals. Based on nuclear SSR data, East and west Mediterranean oleaster populations appear to be differentiated, as shown in previous studies (Besnard et al, 2001c(Besnard et al, , 2002Lumaret et al, 2004). The phenetic analysis and the FCA (Figures 2 and 3b) placed both South Australian populations at an intermediate position between the two main groups of native populations with some cultivars and oleasters from Libya and Tunisia.…”