Micropropagation of Pinus taeda L. from Juvenile Material

The purpose of this study was to develop a protocol for the micropropagation of Pinus taeda from juvenile material. Apical shoots and nodal segments were inoculated into MS, DCR or WV medium. After 90 days, the explants were transferred to WV5 medium supplemented or not with 6-benzyladenine (BA) (2.0 μM) in order to induce multiple shoot formation. For root induction, a medium composed of water and agar and a combination of 1-naphthaleneacetic acid (NAA) (2.69 M) and BA (0.44 M) was used for periods of 7, 9 or 12 days followed by transfer to growth regulator-free GDm/2 or GDm/4 medium. During in vitro establishment, nodal segments showed better responses than apical shoots, with an average of 4.3 to 5.8 shoots per explant after 90 days of culture. WV5 medium proved better than all other media due to a higher survival rate (86%) and higher elongation percentage (85.2%). BA did not promote better multiplication compared to the control, with approximately 2.4 to 3.0 shoots per explant. The alternate use of BA concentrations (2.00, 0.25 and 1.00 μM in each subculture) in WV5 culture medium can increase the multiplication rate. The estimated production was 7530 shoots from 100 explants in 9 months of culture. The best rooting percentage (47.5%) was obtained when shoots were inoculated in a medium with 2.69 M NAA and 0.44 M BA for 12 days. In the roots derived from calluses, the vascular connection was established when roots were longer than 0.6 cm and this size was recommended as the minimum for transplanting. Acclimatized plants showed 90% survival after 90 days. It can be concluded that micropropagation of P. taeda from axillary buds excised from seedlings is feasible. _____________________________________________________________________________________________________________