Basal Salt Composition, Cytokinins, and Phenolic Binding Agents Influence In Vitro Growth and Ex Vitro Establishment of Magnolia 'Ann'

In vitro growth responses of Magnolia 'Ann' to basal salt composition, cytokinins, and phenolic binding agents were investigated in a series of experiments to refine micropropagation protocols. Murashige and Skoog (MS), half-strength MS, Woody Plant Medium (WPM), Driver and Kuniyuki (DKW), and Blaydes basal salts in conjunction with 1 g.L-1 activated charcoal (AC) or 1 g.L-1 polyvinylpyrrolidone (PVP) were evaluated as multiplication media. Benzylaminopurine (BAP), meta-topolin (mT), or 6-(gamma,gamma-dimethylallylamino) purine (2iP) at 2, 4, or 8 mu M was investigated to optimize the cytokinin concentration. Murashige and Skoog medium supplemented with 2 mu M BAP with no phenolic binding agent was an optimal multiplication medium that yielded 3.2 +/- 0.2 shoots with a mean length of 17.2 +/- 1.8 mm over an 8-week period. For rooting, microshoots were cultured on half-strength MS media supplemented with 0, 5, 10, or 20 mu M indolebutyric acid (IBA) with or without AC. Media containing AC produced elongated microshoots suitable for rooting and ex vitro establishment. Microshoots cultured on medium supplemented with AC also had higher in vitro rooting (16%) and higher ex vitro rooting (75%) compared with those without AC regardless of in vitro IBA concentration.