Adventitious shoot regeneration from in vitro leaves of formosan sweetgum (Liquidambar formosana L.)

Plantlets were regenerated from in vitro-grown leaf explants of five genotypes of Liquidambar formosana on WPM basal medium supplemented with different concentrations of TDZ and NAA. With the addition of 0.27 mu M NAA, regeneration efficiency was increased by 2- to 4-fold over that with TDZ alone. Lower concentrations of TDZ (0.45-2.27 mu M) were beneficial for regenerating shoot clusters. Four genotypes (P2, P6, P9, and P11) showed high regeneration rates (up to 90%), whereas genotype P13 showed a low capability for shoot regeneration on all media tested (< 35%). For all five genotypes, the optimum medium for inducing adventitious shoots was WPM supplemented with 1.14 mu M TDZ and 0.27 mu M NAA, on which regeneration rate ranged from 72.6% to 89.5% and adventitious shoot clusters per regenerating leaf explant ranged from 2.63 to 3.11 in four genotypes (P2, P6, P9, and P11), while for P13, the regeneration rate and number of shoot clusters per regenerating explant were 23% and 1.39, respectively. Transfer of shoot clusters to WPM basal medium containing 0.54 mu M NAA, 2.22 mu M BA, and 1.44 mu M GA(3), resulted in shoot elongation. All the elongated shoots were rooted on WPM supplemented with 9.84 mu M IBA, and plantlets were transplanted to soil successfully. Chemical names used: 6-benzyladenine (BA), gibberellic acid (GA(3)), indole-3-butyric acid (IBA), 1-naphthalene acetic acid (NAA), plant growth regulator (PGR), thidiazuron (TDZ), woody plant medium (WPM).