title: Centennial olive trees as a reservoir of genetic diversity.
abstract: OBJECTIVE
  Genetic characterization and phylogenetic analysis of the oldest trees could be a powerful tool both for germplasm collection and for understanding the earliest origins of clonally propagated fruit crops. The olive tree (Olea europaea L.) is a suitable model to study the origin of cultivars due to its long lifespan, resulting in the existence of both centennial and millennial trees across the Mediterranean Basin.
  
  
  METHODS
  The genetic identity and diversity as well as the phylogenetic relationships among the oldest wild and cultivated olives of southern Spain were evaluated by analysing simple sequence repeat markers. Samples from both the canopy and the roots of each tree were analysed to distinguish which trees were self-rooted and which were grafted. The ancient olives were also put into chronological order to infer the antiquity of traditional olive cultivars.
  
  
  RESULTS
  Only 9·6 % out of 104 a priori cultivated ancient genotypes matched current olive cultivars. The percentage of unidentified genotypes was higher among the oldest olives, which could be because they belong to ancient unknown cultivars or because of possible intra-cultivar variability. Comparing the observed patterns of genetic variation made it possible to distinguish which trees were grafted onto putative wild olives.
  
  
  CONCLUSIONS
  This study of ancient olives has been fruitful both for germplasm collection and for enlarging our knowledge about olive domestication. The findings suggest that grafting pre-existing wild olives with olive cultivars was linked to the beginnings of olive growing. Additionally, the low number of genotypes identified in current cultivars points out that the ancient olives from southern Spain constitute a priceless reservoir of genetic diversity.
authors.affiliation: Departamento de Agronomía, Campus Universitario de Rabanales, Ctra. Madrid-Cádiz Km. 396, Córdoba, Spain. g62mudim@uco.es
authors.forename: Concepción M
authors.initials: CM
authors.lastname: Díez
authors.forename: Isabel
authors.initials: I
authors.lastname: Trujillo
authors.forename: Eladio
authors.initials: E
authors.lastname: Barrio
authors.forename: Angjelina
authors.initials: A
authors.lastname: Belaj
authors.forename: Diego
authors.initials: D
authors.lastname: Barranco
authors.forename: Luis
authors.initials: L
authors.lastname: Rallo
mesh_terms: D017343:Genes, Plant; D014644:Genetic Variation; D018895:Microsatellite Repeats; D031658:Olea / Q000235:genetics*; D010802:Phylogeny; D018515:Plant Leaves / Q000235:genetics; D018517:Plant Roots / Q000235:genetics; D013030:Spain