In vitro Propagation of Cedar (Cedrela odorata L.) from Juvenile Shoots

Nodal segments were taken from 12-wk-old shoots induced in modified MS basal medium as already described. For shoot induction and efficient plant elongation, this medium was supplemented with the following auxin treatments: 1) IAA 1.0 mg L-1 (5.70 µM); 2) IAA 2.0 mg L-1 (11.42 µM); 3) IAA 3.0 mg L-1 (17.12 µM); 4) NAA 1.0 mg L-1 (5.37 µM); 5) NAA 2.0 mg L-1 (10.7 µM); and 6) NAA 3.0 mg L-1 (16.07 µM). Effect of PGR on leaf and stem development. Morphogenic response and plant development showed a direct relationship in the culture mediums with the best results (Figure 1). Treatments with 17.12 µM IAA, 10.7 µM, and 16.07 µM NAA induced the best leaf formation and stem development with significant differences with other treatments (Figure 1A). In these media, it was observed that the leaf lamina of the in vitro plants developed better, and it is probable that this effect is related to a better photosynthetic efficiency that has influenced plant development and higher rooting. In the case of the 17.12 µM IAA treatment, a similar number of leaves was observed with regards to the treatments with the best results. Likewise, the number of nodal segments was benefited more in the treatments supplemented with 17.12 µM IAA and NAA at 10.7 and 16.07 µM, and differed significantly from the other treatments (Figure 1B). The greater number of nodal segments can benefit a higher multiplication rate and greater efficiency of the in vitro propagation protocol. In woody species, propagation from nodal segments can be limited by the low nodal formation and scarce separation of these, which complicates its manipulation. For Melia azedarach L., a good response has been obtained in nodal segments cultured in MS medium supplemented with IAA (0.06 µM) and BAP (4.44 µM), as well as with IAA and kinetin (4.65 µM) (Thakur et al., 1998). For C. odorata nodal segments cultured in vitro from juvenile plants, 1 cm long shoots were obtained in basal MS medium supplemented with 2.2 µµ BAP although no significant differences were found with the other treatments with 2-iP and kinetin (Pérez et al., 2002). The best response for Melia azedarach L. was obtained for growth and nodal formation at low IAA levels while height was favored when IAA levels increased (Thakur et al., 1998). In S. macrophylla, the best nodal emission was obtained with BAP at 4 mg L-1 (17.76 µM), and adding NAA or IAA to the medium at different concentrations benefited root and plant height development (Astorga et al., 19