Genetic characterisation of olive trees from Madeira Archipelago using flow cytometry and microsatellite markers

In this study, native olive plants from Olea maderensis (≡ O. europaea ssp. cerasiformis) and O. cerasiformis (≡ O. europaea ssp. guanchica), wild olives (O. europaea ssp. europaea var. sylvestris) and cultivated olives (O. europaea ssp. europaea var. europaea) were analysed with respect to genome size and microsatellite markers. The mean nuclear DNA content of O. maderensis was estimated as 5.97 ± 0.191 pg/2C, while the remaining studied taxa presented mean genome sizes ranging from 2.99 to 3.18 pg/2C. These data and the obtained simple sequence repeats (SSR) profiles, i.e., with 2–4 alleles in O. maderensis and a maximum of two alleles in the other taxa, enabled the identification of a new ploidy level, tetraploidy, for a species belonging to the Olea genus. Cluster analysis of the microsatellite data revealed a clear separation of each species in different clusters and a high genetic dissimilarity could be observed among genotypes belonging to different species. This work contributed to a better characterization of olive species and the obtained data can be helpful to support taxonomic studies, and to develop germplasm preservation strategies in endangered populations of O. maderensis from Madeira Archipelago.