DNA fingerprinting and genetic relatedness among cultivated varieties of Olea europea L. estimated by AFLP analysis

Amplified fragment length polymorphism (AFLP) analysis was used to evaluate the genetic biodiversity and variability present in some Italian varieties of cultivated olive. A group of 12 genotypes belonging to three varieties was screened using six different AFLP primer combinations. A total of 274 loci (59.8% of which were polymorphic) were investigated. The number of polymorphic loci detected by single primer combination for each variety was calculated. AFLP banding patterns were transformed into binary data of presence–absence and matrices were processed with NTSYS-PC and ARLEQUIN software programmes. Similarity relationships were described graphically by a dendrogram which clustered accessions of the same cultivar. Analysis of molecular variance (AMOVA) revealed greater variation among cultivars than within them, but significant intra-cultivar differentiation was found. For the varieties analysed, the data revealed significant genetic diversity in the cultivated olive tree, despite the fact that they come from a limited geographical area. The DNA fingerprinting technique used was confirmed to be a reproducible and sensitive tool for the study of population genetics of olive trees. The high genomic polymorphism observed suggests a more complex genetic population structure than the conventional variety or cultivar level. The present study confirms the importance of considering the degree of genetic relatedness and variability within populations during clone and variety selection programmes.