Cytokinin-mediated shoot induction and liquid culture-enhanced rooting in Turkish hazelnuts (Corylus avellana L.)

Three commercially important Turkish hazelnut (Corylus avellana L.) cultivars (‘Tombul’, ‘Çakıldak’, and ‘Foşa’) were evaluated to optimize an in vitro propagation protocol. The effects of different cytokinins; benzyladenine (BA), zeatin (ZT), meta-topolin (mT), and thidiazuron (TDZ) were tested at 1, 2, and 3 mg L− 1 in the presence of 0.01 mg L− 1 indole-3-butyric acid (IBA). TDZ at 1 mg L− 1 promoted high shoot multiplication, whereas higher TDZ concentrations reduced shoot proliferation and were associated with increased hyperhydricity, shoot tip necrosis, and callus formation. BA supported high shoot multiplication and elongation at specific concentrations, and mT also resulted in long shoots with minimal physiological disorders. Callus formation was most pronounced under TDZ treatments, reaching 100% at 2 and 3 mg L− 1 in all cultivars. For rooting, micro-shoots were cultured on media containing 1 or 2 mg L− 1 IBA solidified with different gelling agents or maintained as liquid culture. Rooting responses differed among cultivars and were influenced by both IBA concentration and rooting system. High rooting percentages, root numbers, and root lengths were obtained in liquid medium and in phytagel, and plant agar solidified media supplemented with 1 or 2 mg L− 1 IBA, whereas bacto agar generally resulted in lower rooting performance. Overall, ‘Foşa’ exhibited lower rooting responses compared with ‘Tombul’ and ‘Çakıldak’.