In vitro shoot necrosis is a quite widespread disorder affecting raspberry micropropagation. This study was conducted to investigate effects of calcium gluconate and ascorbic acid on shoot necrosis and dieback of raspberry shoots during micropropagation. Nodal segments of primocane-fruiting raspberry cultivars ‘Allgold’, ‘Erika’, and ‘Polka’ when cultured on Murashige and Skoog (MS) medium containing 0.6 mg·L-1 6-benzyladenine (BA) and 1 g·L-1 calcium gluconate, showed lower explant browning and shoot necrosis and resulted in higher shoot initiation rate in all three cultivars. Ascorbic acid, at 50 and 100 mg·L-1, increased fresh weight of microshoots of all three cultivars. Although culture medium containing calcium gluconate was found to reduce shoot growth and multiplication of ‘Allgold’ and ‘Erika’ compared to control, an addition of 1 g·L-1 calcium gluconate into MS medium containing 0.6 mg·L-1 BA, at shoot induction stage, is recommended to prevent explants browning and shoot necrosis during raspberry micropropagation.
Key words: Explant dieback, nodal culture, shoot multiplication, tissue culture.