DNA-typing of hazelnut: a universal methodology for describing cultivars and evaluating genetic relatedness

The European hazelnut (Corylus avellana L.) is the source of many commercial nuts and the most important cultivars in Europe and Turkey were selected, over many centuries, from local wild populations of this species. Methods for identification of hazelnut cultivars are primarily based on analysis of morphological traits. These, however, are often unreliable or imprecise indicators of plant genotype, being influenced by environmental factors. Thus discrimination among closely related cultivars and clones is often extremely difficult, above all in nursery, when plants are young and not yet bearing nuts. For these reasons, DNA-typing can be a convenient method for accurately identifying hazelnut cultivars. Microsatellite or Simple Sequence Repeat (SSR) markers show many characteristics of the ideal molecular marker: abundance in the genome, reproducibility, a high level of polymorphism, and co-dominant inheritance. Recently SSR markers have been developed and characterized in C. avellana. From available loci, twelve were selected for high polymorphism and clearness of profile and used for the genetic identification of the most important commercial cultivars of hazelnut, using a semi-automated technique based on fluorochrome technology. The fingerprints of cultivars were defined by their genetic profiles across loci, and the data were expressed in a format suitable for constructing a database. Statistical analysis was applied to investigate informative content and discriminative power of the loci, probability of identity, possible parentage and phylogenetic relationships among cultivars. The methodological approach and the perspectives of the technique are discussed in view of its application at international level and for genetic certification of propagated material