Abstract
A method for micropropagation of two red raspberry (Rubus idaeus) clones from the Norwegian red raspberry breeding programme by shoot tip cultures was tested. Both clones (N71-B3: DistadxViking and N71–2709: VikingxVeten), showed promising regeneration rates. They were micropropagated using modified MS medium and the medium of Anderson. The cytokinin/auxin ratio and the time of introduction of the hormones to the cultures was varied. The meristems were subcultured to fresh medium every 4 weeks. Growth started after one cycle in culture. After 10 weeks in culture several leaves were formed, and multiplication started. The average multiplication factor differed for both clones and media and no regeneration was obtained when auxin levels exceeded the level of cytokinin. The highest multiplication factors (3–4) were found for N71-B3 on Anderson medium. Microshoot quality was classified with respect to shoot size. Clone N71-B3 had more medium sized and large shoots on Anderson medium than on MS, while these differences were not as marked for N71–2709. Cytokinin levels were ranged from 0 to 3.0 mg/l and were tested for multiplication factor and shoot size for N71-B3 in both media. Increasing amounts of cytokinin generally gave increasing amounts of small shoots, but increasing the level above 0.6 mg/l had no further effect on the multiplication factor. Shoot tips were rooted in the greenhouse directly in peat and plantlets were evaluated for growth capacity after rooting. The highest rooting percentage obtained was 97.4% and there was a positive correlation between high rooting percentages and succeeding growth. In the summer of 1989, the plantlets were planted in field experiments to study growth and phenological characters.