Evaluation of ‘Tonda di Giffoni’ hazelnut (Corylus avellana L.) clones

‘Tonda di Giffoni’ is among the most highly appreciated Italian hazelnut (Corylus avellana L.) cultivars. Due to its round kernels and excellent processing quality, it was awarded a Protected Geographical Indication (PGI) from the European Union. To identify clones expressing improved nut and production qualities, a ‘Tonda di Giffoni’ clonal selection programme was conducted across hazelnut orchards in the Irno valley of Italy from 1995 to 2006. One hundred different clones were selected and propagated in a replicated trial under similar climate, soil, and cultural conditions. From this work, the 29 best clones were identified and from 2006 to 2008 their agronomic and pomological characteristics were observed. Microsatellite or simple sequence repeat (SSR) markers were used to successfully confirm true-to-type identity of the clones. Traits evaluated included flowering time (anthesis), bud break, suckering, trunk diameter, nut and kernel characteristics and productivity (yield). Best linear unbiased predictions for clone means and estimates of intraclass correlation coefficient were obtained using R environment, lme4 and ggplot2 packages. Five clones superior to that of the standard of ‘Tonda di Giffoni’ were identified in this study. Furthermore, yield and number of suckers produced showed sufficient variability to likely be exploited for breeding. The selected clones express features useful for both growers and the processing industry and will be propagated and planted in hazelnut orchards for further study and commercial production.