Application of additive light increases leafy cutting rooting and survival in hazelnut (Corylus avellana L.)

Corylus avellana is a hard-to-root species, thus hazelnut cultivar propagation by stem cuttings is considered difficult. The rooting of cuttings is influenced by many exogenous and endogenous factors such as hormones, cutting quality, and environmental conditions. In particular, rooting success of soft wood cuttings could be enhanced by the application of additive light during rooting due to the possible increase of photosynthetic activity of the cutting leaf and of the consequent increase of the carbohydrate content of the cutting. The aim of the present work was to evaluate the effect of additive light during the rooting process on cutting physiology and rooting success. Results showed that additive light (PAR ~300 μmol m-2 s-1), applied in 2014 on cuttings of 'Tonda di Giffoni', increased cutting leaf photosynthesis and cutting non-structural carbohydrate content. This resulted in a consistent increase of the percentage of rooted cuttings and of the quality of the roots. Furthermore, plants obtained from rooting under the additive light condition suffered a reduced amount of mortality in comparison with control plants. The experiment was repeated in 2015 on a pre-commercial scale using 'Tonda di Giffoni' and 'Tonda Romana' cuttings. Results confirmed the observation of the previous year. In conclusion, additive light during leafy cutting rooting is a technique able to increase cutting propagation success in hazelnut.