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Variability of wild olives (Olea europaea subsp. europaea var. sylvestris) analyzed by SSR markers and agro-morphological traits

Wild olives (Olea europaea subsp. europaea var. sylvestris) represent a distinctive element of Mediterranean flora and an important genetic source for resistance to biotic and abiotic stresses in olive selection and breeding. In this study, genetic diversity among 48 wild genotypes sampled from four different sites from two provinces of Andalusia (Cadiz and Jaen), Southern Spain, was evaluated by means of SSR markers and agro-morphological traits. SSR markers revealed high genetic variability among the genotypes. The cluster analysis based on their polymorphism indicated a certain grouping of wild olives according to their sampling sites. The 20 agro-morphological traits evaluated showed a high variation between genotypes and significant correlation coefficients were obtained among the values recorded in two consecutive harvest seasons, 2007/08 and 2008/09 (r: 0.59-0.78). Traits such as pit shape, fruit symmetry (position A) and oil content on dry basis were very useful in genotype discriminating. The average values obtained in wild olives for fruit size and oil content were lower than the previously reported in cultivated material. However, it is worth mentioning that individuals with fruit weights (1.3 g) and olive oil percentage in dry matter (33.8%) comparable to the values found in some olive cultivars, were also found. With both DNA based and agro morphological descriptors, higher levels of variability were found within each site than between sites. Genetic variation observed among the wild olive germplasm at the DNA level was higher than the agro-morphological traits, indicating the efficiency of SSR markers for detecting genetic diversity among wild olive genotypes and their relationships. Molecular data obtained by SSR markers together with in situ morphological and agronomical characterization of wild olive trees confirmed the high diversity found within the wild populations evaluated. These results indicate the richness of wild olive genetic resources in Andalusia.

wild olives; SSR markers; morphological traits; plant genetic diversity

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