Investigation on clonal variants within the hazelnut (Corylus avellana L.) cultivar 'Tonda Gentile delle Langhe'

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 2 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 an ex situ 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 ex-situ trial 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 2 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.