Genetic relationships between oleander (Nerium oleander L.) accessions by means of AFLP profiling

Oleander (Nerium oleander L.) is a Mediterranean evergreen shrub widely grown as an ornamental for its abundant and long-lasting flowering as well as its moderate hardiness. Genetic relatedness among 71 accessions, including commercial varieties, different sources of the same varieties, and selections from the wild were investigated using amplified fragment length polymorphism (AFLP). Genetic similarities among accessions were calculated according to Jaccard's Similarity Index and used to construct a dendrogram based on the unweighted pair group method, using arithmetic averages. Our results show that up to about 9% molecular genetic differentiation was detected among morphologically indistinguishable provenances of the same variety. This can be partly attributed to scoring error but mainly to somatic variation occurring during vegetative propagation. On the other hand lower genetic distance values were sometimes found among varieties, which differ in morphological characters and are thus commercialised with different names. The possibility of considering the amount of genetic variation within a variety as the threshold value for discrimination of initial varieties and essential derivative varieties is discussed.