Abstract:
The timber and Christmas tree industries are important components of the Pacific Northwest economy. A goal of both industries is to produce high quality trees with high growth rates. Accomplishing this requires increased genetic quality of the trees grown. Tissue culture provides the most promise for propagating these superior genotypes. Douglas-fir has been tissue cultured previously, however, multiplication rates were low and success with mature material was limited. Recent research found that a double-phase tissue culture system significantly increases multiplication rates of fruit and nut trees. A doublephase system consists of the conventional solid layer overlaid by a liquid layer. Therefore, the objective of this study was to test a double-phase micropropagation system of Douglas-fir, particularly mature clones. Preliminary experiments were performed on juvenile Douglas-fir to test media and media components while waiting to obtain mature material. Preliminary experiments concluded that 1) Dunstan B-2 medium provides better multiplication rates compared to SEM medium; 2) activated charcoal is a beneficial addition to the medium; 3) a low hormone liquid phase may be superior to a high hormone liquid phase and to no liquid phase; and 4) there does not appear to be a significant difference between 0.25%, 1 %, and 2.5% activated charcoal addition to the solid medium. In the final experiments using mature shoots, hormone-free doublephase medium stimulated more growth than single-phase or other double-phase media. This indicates that double-phase culture has potential for improving micropropagation of Douglas-fir.
