Assessment of genetic variability of olive varieties by microsatellite and AFLP markers

Fourteen developed microsatellite markers were characterized for their use in genotyping and diversity studies of olive varieties. After optimisation of microsatellite assay and allele sizing, ninety-six alleles were found in nineteen varieties, with an average of 6.8 alleles per locus. The characteristics of the microsatellite markers were used to identify markers that can be reliably applied for variety genotyping. Such features were the generation of complex banding patterns supported by underlying allele sequences, `short allele dominance', an unstable repeat structure and a low number of alleles. AFLP analysis was performed on the same set of olive varieties using eight primer pair combinations. The genetic relationships among nineteen olive varieties were compared on the basis of microsatellite and AFLP polymorphisms. Genetic distances between all pairwise combinations of the varieties were calculated using Jaccard's coefficient of similarity and dendrograms were constructed by the UPGMA method. The results of clustering analysis with both molecular systems showed the common genetic background of Tuscan varieties, and genetic divergence within Slovene olive germplasm. Slovenian varieties ‘Buga’, ‘Štorta’ and ‘Samo’ might represent regionally selected olives, while ‘Zelenjak’ and ‘Črnica’ are probably derived from the Central Italian region. The predominant local ‘Istrska belica’ was introduced to Slovenia independently from the other regional varieties and showed the lowest genetic similarity with the other regional varieties.