Genetic diversity is the basis of plant breeding. Precious
biodiversity is being lost with the disappearance of
numerous wild plant species, mainly because of overexploitation and loss
of habitat. Many wild plants have medicinal uses. They
tend to become more valuable the scarcer they become. This encourages
people to gather them to sell, and puts heavy
pressure on surviving populations.
Tissue culture techniques are being widely used for the propagation and conservation of many traditional
Chinese medical plants Fig. 1, Fig. 2. and Fig. 3. Some of them are becoming rare in the wild. The conservation of germplasm
in vitro keeps these species safe from accidental extinction. The techniques also make available a large body of material
for pharmacological studies and chemical analysis.
They also provide large quantities of disease-free seedlings for farmers. Tissue culture has made possible the
mass production of disease-free and uniform plants. The technique thus brings farmers the great benefit of high-quality
planting materials of new high-value crops
Finally, these same techniques can be used for the safe transfer of germplasm from one country to another. Many
of the diseases and pests which damage agriculture today were introduced accidentally when new crop varieties were
imported from overseas.
So much damage has already been done from these accidental invasions, that it is becoming difficult for countries
to exchange plant materials. Many governments tend to feel that the possible damage from introductions may well
outweigh any potential benefits. However, plant breeding programs need access to new germplasm.
Tissue culture offers a solution to the problem. Germplasm can cross international boundaries safely, in the
assurance that no pests and diseases are secretly traveling with it.
In recent years, remarkable progress in molecular biology techniques has enabled scientists to acquire a more
detailed understanding of plant pathogens. This training course introduced participants to current techniques of serological
and molecular diagnostic techniques.
Serological assay is based on antibodies produced by animals, usually rabbit or rats. When suitable antibodies
are available, the most sensitive and efficient test for plant virus is ELISA (=enzyme-linked immunosorbent assay). ELISA
is widely used, since it is easy to apply and does not need any expensive equipment.
Another testing method is PCR (=polymerase chain reaction). PCR
testing is very accurate, but it is also
rather expensive and technically difficult. The participants were shown
the preparation of samples for PCR testing, including
the precautions needed to avoid the contamination of samples. They
then practiced the steps themselves in laboratory exercises.
The DNA composition of an individual plant is what determines its essential characteristics. The DNA
fingerprint describes the DNA sequence profile of an individual. This is the same in every cell of that individual.
The DNA fingerprint cannot be altered by any change in the environment. Nor can it be changed by anything
that happens to an individual during its lifetime.
Different DNA markers are available, including RFLP (restriction fragment length polymorphism), RAPD
(random amplified polymorphic DNA) and AFLP (amplified fragment length polymorphism).
These markers are used to characterize a variety or line, and in this way protect the intellectual property rights of
the plant breeder. They are also used to evaluate the purity of seeds, and to detect genetic drift in germplasm collections.
It is also advisable to use the material for only five generations, or only five sub-culturing cycles.
Held at PCARRD, Philippines, on December 1-7
No. of countries participating: 10 (Bangladesh,
Hong Kong, India, Japan, Korea, People's Republic of China,
Philippines, Taiwan ROC, Thailand, Vietnam)
No. of papers presented: 10
No. of participants: 25
Co-sponsors: Taiwan Agricultural Research Institute
Asia and Pacific Seed Association
Philippine Council for Agriculture, Forestry and Natural Resources Research and Development
Figure 1 Embryos Developing from Callus
Figure 2 Tissue Culture of C. Yanhusuo, Embryos with Shoots and Roots
Figure 3 Tissue Culture of C. Yanhusuo