In vitro rooting of hybrid hazelnuts (Corylus avellana×Corylus americana) in a temporary immersion system

Abstract

Commercial micropropagation of hybrid hazelnuts (Corylus avellana L. × C. americana Marshall) has been limited, owing to their poor rooting ability in vitro as well as ex vitro, leading to high mortality of plantlets transplanted in the greenhouse. The objective of this study was to develop an efficient and cost-effective protocol for rooting and plantlet acclimation of in vitro grown hazelnut shoots. Efficient in vitro rooting was accomplished in a rocker-based temporary immersion bioreactor system. The use of a temporary immersion system (TIS) in combination with the inert substrate Oasis® In Vitro Express (IVE) significantly improved the in vitro rooting efficiency (100%) compared with semi-solid medium (27%) after four weeks of culture. A higher density (36 explants/vessel) of shoot explants in the TIS was found to support a significantly greater shoot height, chlorophyll content, and longest root length, compared with the lowest density treatment (12 explants/vessel). Efficiency of rooting and the number of roots formed were similar for both the high and low density of explants in the culture vessels, and the resulting plantlets exhibited > 80% survival in the greenhouse. These results demonstrate the usefulness of rocker-based TIS for commercial micropropagation of hazelnuts and, potentially, other tree species.