Protocols for Micropropagation of Woody Trees and Fruits

472 V.M. JIMÉNEZ AND E. GUEVARA
Figure 4. Multiplication of the developed shoot clumps. A) Scheme of a shoot clump with
possible cutting sites (the red line indicates site of shoot clump division, while blue lines are
for multiplication through single nodes), B) Newly transferred small shoot clumps after
division of the large ones.
If PPM or a similar compound was included into the culture medium to deal with
contamination problems (see Section 2.2.2), start eliminating this compound from
the culture medium in part of the culture vessels at each subculture. This would
allow expression of endogenous latent contamination and therefore allows selection
of contaminant-free shoot clumps. PPM inhibits growth of microorganisms, but at
the same time masks endogenous contamination.
2.5. Rooting
For root induction, transfer well developed actively growing shoot clumps to the
rooting medium (see Table 5). If gelled culture medium does not induce rooting,
transfer large shoot clumps into large-volume vessels containing a relatively thin
film of liquid medium (1 cm in depth), which avoids the necessity of shaking the
cultures. In other cases, rooting can be induced ex vitro by dipping the shoots in 200
mg l –1 IBA and planting them in polyethylene bags containing sterilized soil and
vermiculite (1:1) (Ravikumar et al., 1998).
In Bambusa vulgaris ‘Striata’, a conditioning treatment with 0.1 mg l –1 thidiazuron
and exposure to continuous light (48 µmol m –2 s –1 ) for two to three subculture cycles
of 2 weeks each, before applying the PGR combination indicated in Table 5 for this
species, considerably enhanced rooting (Ramanayake et al., 2006). Rooting has also
occurred spontaneously in the same medium used for shoot and plant multiplication
in Dendrocalamus strictus (Shirgurkar et al., 1996) and Guadua angustifolia
(Jiménez et al., 2006).