Genetic diversity and clonal variation within the main Sicilian olivecultivars based on morphological traits and microsatellite markers

Abstract

The richness of Olea europaea (L.) genetic resources in Sicily is well documented. In the last 30 years, mostof the local cultivars, landraces and ecotypes have been gathered together in a large ex-situ collection,containing more than 300 genotypes. In this study, 45 putative clones of the main Sicilian olive cultivarswere characterized morphologically using microsatellite markers to unambiguously identify possiblesuperior genotypes. The microsatellites employed were polymorphic (observed heterozygosity = 0.71;polymorphic information content = 0.59), discriminated 52% of the genotypes and enabled the detectionof intra-cultivar polymorphism, derived from both somatic mutations, indicating the presence of poly-clonal cultivars, or from gametic origin, thus suggesting the presence of cultivar-populations. A high levelof genetic variability was detected within the ‘Biancolilla’, ‘Giarraffa’ and ‘Moresca’ genotypes, whereaslow variation was found within the ‘Cerasuola’ and ‘Tonda Iblea’ genotypes. The combination of UPGMAcluster analysis of data obtained from microsatellite analysis, with canonical discriminant analysis (CDA),based on 18 morphological variables, measured under the same conditions, enabled intra-cultivar diver-sity, attributable to genetic factors rather than to environmental ones to be identified. The goodness offit between microsatellite profiles and the CDA analysis was significantly supported by the Mantel test(r = 0.3; p < 0.001). Genotypes and clonal variants with superior traits (larger fruit size; compact tree habit,apt for high density planting; higher oleic acid content) were identified, suitable for enlarging their areaof cultivation.