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CIAT
has been developing and implementing in vitro systems
for cassava since the 1980s. Procedures include cleaning cassava
of pathogens (especially those of viral and bacterial origin),
micropropagation, conservation, and germplasm exchange.
Two propagation schemes are currently being followed, one
that is low-cost and the other for mass production. The first
scheme uses a participatory approach, which was first developed
with a group of women farmers in the Department of Cauca,
Colombia, with support from FIDAR, CBN, and PRGA.
The scheme succeeded in establishing a facility for in
vitro propagation in the field, replacing conventional
laboratory inputs and equipment but maintaining the propagation
rate (1:3).
The second scheme, involving RITA®
bioreactors, increases the efficiency of solid-system propagation
from 1:3 to 1:10-12. In this system, explants are periodically
bathed, for short periods, in liquids containing high dosages
of cytokinins.
CIAT holds in trust the most complete world collection of
in vitro cassava, with about 6000 entries stored in
a space of no larger than 40 m2. This active collection supports
the material exchange systems of cassava germplasm certified
as virus-free. Material conserved this way must be periodically
subcultured to fresh mediums.
To establish complementary conservation systems for cassava,
research is being conducted on systems of conservation in
liquid nitrogen known as cryoconservation. Studies carried
out with cassava apices made possible the establishment of
a conservation system using programmers thereby achieving,
for most of the tested clones, the recovery of material after
freezing. Currently, encapsulation-dehydration systems are
being developed to permit simple manipulations of the material
during freezing. Preliminary trials with a sample from the
core collection have shown the comparative advantage of this
technique, compared with classic systems.
Protocols of cryoconservation have also been developed for
cassava seeds and friable embryogenic callus, and some fruit
trees.

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