Résumé
Despite the socio-economic importance of olive oil and the need of olive breeding, genetic studies on agronomic traits are restricted to few biparental populations limiting the efficiency of QTL (Quantitative Trait Loci) mapping strategy. Association mapping based on a diversified collection of olive germplasm can be proposed as a complementary strategy to genetically map agronomic traits. Here, we aimed to develop tools for association mapping studies by defining a Mediterranean olive core collection and characterizing a massive set of microsatellite markers (SSRs). The worldwide olive germplasm bank of Marrakech, Morocco (561 accessions from 14 Mediterranean countries) was characterized using 17 nuclear SSRs and cpDNA markers and classified into east, centre and west Mediterranean gene pools. Combining two sampling methods maximizing the capture of diversity and genetic distance, we proposed two core collections of 50 and 94 accessions including all nuclear SSR alleles, cpDNA haplotypes and states of agro-morphology (from Olea databases) from the WOGB Marrakech. These core collections include cultivars considered as the most important in Mediterranean olive producing countries and display a limited genetic structure between east and west/center gene pools. Hence, they are efficient candidates for phenotyping agronomic trait and to explore the largest variability in distinct environmental conditions. Concurrently, we developed a set of genomic and Expressed Sequence Tag (EST)-derived SSRs that were used to complete the genetic map of ‘Olivière’ × ‘Arbequina’ segregating population. Molecular markers will be used on the proposed core collections to assess the linkage disequilibrium decay according to the genetic distance and to further develop association mapping studies.