Efficient organogenesis and plantlet regeneration in the timber species Cunninghamia lanceolata (Lamb.) Hook

Two efficient regeneration systems were developed in Cunninghamia lanceolata, the most important conifer for industrial wood production in China. Cotyledons and hypocotyls derived from greenhouse-grown seedlings were used as initial explants in our research. A high frequency (95.1 ± 1.84%) of adventitious buds were initiated directly from cotyledons cultured on Douglas-fir cotyledon revised (DCR) medium supplemented with 1 mg l^-1 benzyladenine (BA), 0.1 mg l^-1 α-naphthaleneacetic acid (NAA), and 0.004 mg l^-1 thidiazuron (TDZ) with a maximum mean number of adventitious buds per cotyledon explant of 3.76 ± 0.08. In contrast, a high percentage (93.73 ± 0.55%) of adventitious buds regenerated via callus produced from hypocotyls cultured on DCR medium supplemented with plant growth regulators with a maximum number of adventitious buds per explant (16.71 ± 0.34). Adventitious buds elongated on DCR medium supplemented with 0.2 mg l^-1 BA and 0.02 mg l^-1 NAA. After liquid pretreatment with 50 mg l^-1 indole-3-butyric acid (IBA), over 95% of the shoots successfully rooted on 1/2 DCR medium supplemented with 0.3 mg l^-1 IBA. The innovated systems reported in this study will be useful tools for future genetic manipulation of C. lanceolata and may be adapted for large-scale propagation in other conifers.