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The hazelnut cultivar 'Tonda Gentile delle Langhe' (TGdL) from Piedmont (Northwest Italy) is known worldwide for the excellent quality of its nuts and is thought to have a monoclonal origin. During 3 years of on-farm exploration carried out in Piedmont within the AGRI-GEN-RES project SAFENUT, 6 accessions of a minor cultivar called 'Tonda di Biglini' (TdB), known for its nut quality similar to TGdL, and two plants with low or null suckering habit, found in an orchard of TGdL, were characterized with TGdL reference plants using molecular markers and plant descriptors. In addition, agronomical behaviour and nut quality of TdB were evaluated in a field trial aimed at comparing TdB and TGdL in the same environmental conditions. Although analyses at 27 SSR hazelnut loci revealed the same genetic profile of TGdL for all the considered accessions, observations showed relevant differences in phenological and nut traits: earlier female flowering and nut maturity times (10 days) in TdB than in TGdL; lower percent kernel and higher presence of double kernels in TdB than in TGdL. These results were confirmed in the field trial comparison and were observed also in the non-suckering plants. A sensory analysis conducted on TGdL and TdB kernels using triangle test gave a significant identification indicating organoleptic differences between the two cultivars. In conclusion, given that the distinctive characters found are stable and maintained through propagation as shown in the field trial, TdB can indeed be considered a different cultivar while for the non-suckering individuals the stability of the traits after propagation still need to be confirmed. This report demonstrates the presence of mutations of agronomical relevance within a monoclonal cultivar of hazelnut. © 2013 Elsevier B.V.

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 ten 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 caliber. 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 centers 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 suggest 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.