Development of a sterile cultivation system for rooting of shoot tip cultures (red raspberries) in duroplast foam

In order to improve the availability of oxygen for shoot tip cultures during the course of rooting and to overcome some further agar-related problems a sterile foam cultivation system was developed. Three commercially available foam substrates have been tested, but only a wide pore phenol resin foam proved to be useful in the rooting of red raspberry shoots (Rubus idaeus cv. ‘Gigant’). In comparison to root growth in agarous medium, the newly developed foam cultivation system improved the ramification of the root system, increased the number of root hairs significantly and reduced the friability (lignification) of roots. Also shoot length increased significantly. From the growth experiments it can be concluded that the chemical rather than physical properties of the foam substrate are growth limiting. Still some efforts must be made to improve and standardize the properties of the foam substrate for routine use in mass propagation of organ cultures in vitro.