Data from: Molecular and morphological diversity of on-farm hazelnut (Corylus avellana L.) landraces from southern Europe and their role in the origin and diffusion of cultivated germplasm

Hazelnut (Corylus avellana L.) is a traditional nut crop in southern
Europe. Germplasm exploration conducted on-farm in five countries
(Portugal, Spain, Italy, Slovenia, and Greece) identified 77 landraces.
The present work describes phenotypic variation in nut and husk traits and
investigates genetic relationships using 10 simple sequence repeat (SSR)
markers among these landraces, 57 well-known references cultivars, and 19
wild accessions. Among the 77 landraces, 42 had unique fingerprints while
35 showed a SSR profile identical to a known cultivar. Among the 42 unique
landraces, morphological observations revealed high phenotypic diversity
and some had characteristics appreciated by the market such as nut round
and calibre Analysis of genetic relationships and population structure
allowed investigation of the origin and spread of the cultivated germplasm
in southern Europe. Our results indicate the existence of three primary
centres of diversity in the Mediterranean basin: northwestern Spain
(Tarragona) and southern Italy (Campania) in the West and Black Sea
(Turkey) in the East. Moreover, the data suggests the existence of
secondary gene pools in the Iberian (Asturias) and Italian (Liguria and
Latium) Peninsulas, where local varieties were recently domesticated from
wild forms and/or from introduced ancient domesticated varieties.