DNA fingerprinting and classification of geographically related genotypes of olive-tree (Olea europaea L.)

Abstract

Malaga is a province of Spain where olive-trees are cultivated in a large range of environments, climates and soils. We have developed a reliable and reproducible method to detect RAPD and AP-PCR polymorphisms, using DNA from olive-tree (Olea europaea L.) leaves. Starting from their natural orchards, fifty-six olive-tree cultivars throughout Malaga province, including oil and table olive cultivars, were screened and grouped into 22 varieties. A total of 62 informative polymorphic loci that provide 601 conspicuous bands were enough to differentiate the varieties. Clustering analyses managing 3 different pairwise distances, as well as phylogenetic analyses, led to the same result: olive-trees in Malaga can be divided into three main groups. Group I (90% of certainty) contains wild type and two introduced varieties, group II (83% of certainty) covers some native olive-trees, and group III (58% of certainty) is an heterogeneous cluster that includes varieties originating and cultivated in a number of Andalusian locations. Geographic location seems to be the first responsible of this classification, and morphological traits are needed to justify the group III subclustering. These results are consistent with the hypothesis of autochthonic origin of most olive-tree cultivars, and have been used to support a Label of Origin for the olive oil produced by the varieties included in group II.