Diversity of Olea genotypes and the origin of cultivated olives

Abstract

Tandem repeats belonging to three DNA sequence families ( OeTaq80, OeTaq178, and OeGEM86) were isolated from the nuclear DNA of Olea europaea cv. Carolea and dot-hybridized to the genomic DNA of 14 hypothetically different Olea species, 78 olive cultivars, and 14 wild olives. The copy number per unreplicated haploid genome of OeTaq80- and OeTaq178-related sequences was in the 10(7)-10(6) range and that of OeGEM86-related sequences was in the 10(5) range in cultivars, wild olives and some Olea species. A large variation in the frequency of repeats belonging to each sequence family was observed within each group of plants. Positive correlations existed in each genome between the frequencies of repeats belonging to each family, and their overall frequency was positively correlated to the genome size. Duncan grouping showed that the frequency variation of tandem repeats within each group of plants was not continuous. Two main groups and several subgroups of genotypes could be separated within both the olive cultivars and the wild olives. Discrete areas in the Mediterranean Basin could be delimited by the geographic distribution of cultivated olives with different genotypes and the wild plants were associated with the cultivars in these areas according to genotypic similarity. The Olea species could be divided into four genotypic groups. Three of these, comprising accessions from Asia and North Africa, showed similarity with the genotypes of cultivars and wild olives. These results suggest a polyphyletic origin of cultivated olives from different wild Olea forms distributed throughout the Mediterranean Basin.

The coexistence of oleaster and traditional varieties affects genetic diversity and population structure in Algerian olive (Olea europaea) germplasm

“…Then, both analyses suggest that the present olive collection includes cultivated genotypes genetically related to oleaster germplasm, that we can call ''landraces''. These genotypes may represent the result of gene flow between local cultivars and oleaster genotypes, as expected in areas where the two botanical varieties share a common environment with the oleaster trees located in close proximity to the cultivated fields (Besnard and Bervillé 2000;Contento et al 2002). Hybridization of oleaster and cultivated germplasm, and the long history of exchange of cultivated genetic resources throughout the Mediterranean countries, could have contributed to the low degree of differentiation between oleasters and local olive cultivars in Algeria (Besnard et al 2001).…”

Transferability of olive microsatellite loci across the genus Olea

“…In the past years, several molecular studies, including AFLPs, RAPDs, ISSRs, repetitive DNA sequence analysis and chloroplast and mitochondrial DNA polymorphism, have also contributed to elucidate the classification of the Olea complex and the origin of cultivated olive (Angiolillo et al 1999;Amane et al 2000;Besnard and BervillØ 2000;Hess et al 2000;Besnard et al 2002b, c;Contento et al 2002).…”

Assessing Genetic Diversity in Olea europaea L. Using ISSR and SSR Markers

“…The high level of polymorphism observed was consistent with other comparable studies (Sensi et al 2003;Gemas et al 2004;Lopes et al 2004; Martins- Lopes et al 2007;Gomes et al 2008), confirming that the olive is a highly variable species, a reflection of the agronomic diversity within olive cultivars. The high diversity found between olive cultivars is probably due to a diverse germplasm origin, which presumably results from crosses between wild and cultivated olives, resulting in new cultivars in different parts of the Mediterranean, and low breeding pressures (Besnard et al 2001;Contento et al 2002;Belaj et al 2003). This may also explain why in the combined dendrogram ( Fig.…”