Caracterización morfológica, agronómica y molecular de un banco de germoplasma de olivo silvestre (Olea europaea subsp. europaea var. sylvestris)

The genetic improvement programs of olive tree have been based primarily on intra- specific crossbreeding on the purpose of obtaining new varieties that can meet the requirements of the olive growing sector regarding the early production, oil yield, maturation and harvest time, the ability to mechanical harvesting, oil quality and resistance to biotic and abiotic factors. However, recent studies on wild olive trees or Oleasters (Olea europaea subsp. europaea var. sylvestris) indicated high genetic diversity in these populations and their possible use in olive breeding programs. In this regard, a Germplasm Bank of Wild Olive trees (GBWO) is being established in the center IFAPA Alameda del Obispo, in Cordoba (Spain). A group of wild olive trees and related subspecies from different regions of Spain (Andalusia, Balearic Islands, Canarias and Extremadura) and the Madeira islands (Portugal) are being conserved in this ex situ collection. In addition, two of the conserved wild olive have been used in the Program of Improvement of Olive tree of Córdoba, in crosses with the variety 'Picual'. In the present study a first characterization of the Germplasm Bank of Wild Olive trees has been carried out. In this context, qualitative and quantitative morphological parameters of leaf, fruit and endocarp, and agronomic traits of interest such as vigor, oil yield, and flowering were evaluated in addition to the molecular profile of each oleaster, genotyped by the mean of eight SSR microsatellite loci. Wild olives characterization revealed a great diversity at the morphological, agronomic and molecular level. It should be noted that the variability found in the wild olive populations under study was mainly due to genetic differences within population although significant genetic differentiation between them was found in most cases. The high correlation obtained between in situ and ex situ data for some morpho-agronomic parameters indicate the usefulness of in situ evaluation for a preliminary selection of wild olive populations. The genotyping of the GBWO by means of SSR markers has confirmed their effectiveness in genotype discrimination and management of the collection as well as in the study of the variability found in it. The use of SSRs has evidenced a clear separation of genotypes of the subspecies cerasiformis from Madeira from the rest of the populations under study. In addition the use of SSR markers represented an additional information source to the one obtained by the morpho-agronomical evaluation. In the present work, two progenies originated from crosses between two oleasters and the cultivar ‘Picual’ were compared with the one obtained from the cross of ‘Picual’ and the cultivar ‘Zaity’. The offsprings of the wild olive trees showed low fruit oil content and fruit size, but also a shorter juvenile period compared with the offspring derived from crosses between varieties.