Liquid Culture Systems for in vitro Plant Propagation

198 Elio Jiménez González
1. Introduction
Commercial in vitro propagation is currently applied to several tropical
plants. Among food crops bananas, plantains, sugarcane and pineapples are
the most successful examples. However, in vitro propagation methods are
available for a large number of other tropical plants, which are normally
used on a laboratory scale for research purposes, germplasm preservation or
propagation of selected plants in research or academic institutions.
The present limitation to the wider commercial application of
micropropagation in tropical crops in developing countries is the high cost of
the plants when using the traditional micropropagation methods, e.g.
bananas and plantains (0.15 – 0.30 USD), sugarcane (0.12 – 0.20 USD),
pineapple (0.10 – 0.25 USD) (Pérez et al, 1998).
Labour costs in Latin America are lower compared to developed
countries in North America, Europe or Asia, but still remain as the major
part of propagation costs. Manual labor for in vitro propagated plants in
Latin America represents from 45 – 60 % of total costs (Pérez et al., 1998).
Partial automation of in vitro propagation and especially temporary
immersion systems (TIS) may help to reduce propagation costs (Etienne and
Berthouly, 2002). TIS can increase the efficiency of propagation processes
by reducing the cost as a result of labour reduction, savings in shelf space,
high biological yields, improved plant quality or low investment and
maintenance costs. For pineapple shoot multiplication the application of TIS
resulted in 20 % cost reduction compared to cultures in conventional liquid
medium (Escalona et al., 1999) and sugarcane propagation in TIS saved 46
% of the costs in comparison with the standard procedure in semisolid
medium (Lorenzo et al., 1998).
2. TIS from laboratory to commercial application
TIS have been described for in vitro multiplication of a wide range of
tropical crops such as Ananas comosus, Camellia sinensis, Citrus deliciosa,
Coffea s.p, Colocasia sp., Eucalyptus sp., Hevea brasiliensis, Manihot
esculenta, Musa sp., Psidium guajava, Saccharum sp., Solanum tuberosum
(Table 1). Laboratory protocols have been developed by using different
regeneration systems: Shoot multiplication, somatic embryos (either
multiplication and/or germination) and induction of storage organs
(microtubers).