Genetic diversity of hazelnut (Corylus avellana L.) germplasm in northeastern Spain

In Spain, hazelnut is mainly cultivated in Catalonia, a region in the northeast. The province of Tarragona accounts for 88% of the total Spanish area planted to hazelnut. Almost 80% of the production in Tarragona is of the local cultivar Negret, with others cultivated to a lesser extent. Minor cultivars are only sporadically present in older orchards, farm yards and gardens, and have been collected for preservation. In this work, 16 SSR markers were used to fingerprint 18 minor hazelnut cultivars from northeastern Spain. Their microsatellite profiles were combined with those of 15 Spanish cultivars characterized in a previous work, and used to study the genetic diversity in 33 genotypes including local Spanish germplasm. The SSR analysis allowed development of unique profiles of each of the 18 cultivars, and no new case of synonymy was detected. A high level of genetic diversity (mean H-c = 0.7) was observed in 33 genotypes, although a high number of them showed a close genetic relationship. The dendrogram generated by UPGMA cluster analysis placed the 33 accessions into nine main groups, related to their putative pedigrees or geographical area of cultivation. All investigated Negret-type cultivars were found to be distinct from Negret, and only a few cultivars within this germplasm appeared to be seedlings of Negret. The results will be useful in the conservation of hazelnut germplasm and in the selection of parents for use in breeding.