Development of an efficient regeneration system for the precious and fast-growing timber tree Toona ciliata

Toona ciliata (Chinese mahogany) is an important timber species and secondary protected plant due to excessive exploitation in China. Here we developed a robust and efficient regeneration system for adventitious shoot induction using hypocotyl explants of T. ciliata. To facilitate plant growth, different regulators were added to Murashige-Skoog (MS) medium (0.5 mg/l 6-BA, 1.0 mg/l KT and 0.1 mg/l IBA). A regeneration frequency of 58.67% with four shoots per explant was achieved by horizontal setting of hypocotyls on MS medium and following a 20-day seeding period. MS medium supplemented with 0.3 mg/l 6-BA and 0.2 mg/l NAA was optimal for shoot multiplication and elongation, with a multiplication coefficient of 3.06. A rooting frequency of 93.33% was achieved using the half-strength MS containing 0.1 mg/l NAA. After acclimatization, plantlets were transplanted to sterilized nutrient soil containing a 2 : 1 ratio of vermiculate with 90% survival frequency. Thus, the regeneration system developed in this study would be useful for genetic transformation and other biotechnology endeavours in T. ciliata.