Cain
can gain
Dr
Vibha Dhawan emphasises that the tissue culture of new varieties and
multiplication of the existing disease free varieties might help in
improving per unit productivity of cane.
 |
| Dr
Vibha Dhawan |
In
this era of globalisation, farmers in the developing countries with
smallholdings and meagre resources have a challenging task of competing
in the international markets. While globalisation has offered tremendous
opportunities – whereby a farmer is free to sell his produce not just
in the domestic markets but world over – it has also posed threats,
which cannot be ignored.
The
customer today wants quality produce at a competitive price. Thus,
the marginal farmers in a developing country have the daunting task
of producing quality product as well as compete with large farmers
in industrialised countries, who apart from utilising technologically
advanced seeds, equipment, irrigation facilities and fertilisers also
enjoy farm subsidies.
Being
an agri-based economy, where agriculture contributes over 35 per cent
to the GDP and provides a livelihood to over 65 per cent of the population,
the task before us is to supplement ongoing efforts with newer biotechnological
tools to increase productivity.
INTRICACIES
OF MICROPROPAGATION
Micropropagation
is a technique of producing millions of identical plants from a millimetre
or centimetre long explants collected from an elite plant or seed.
The general techniques of micropropagation involves the following
stages:
- Selection
and preparation of mother plant m Initiation of aseptic culture
- Shoot
multiplication
- Shoot
elongation m Rooting of in-vitro formed shoots
- Transplantation
to potting mix.
Each
stage has its own special requirements specific to individual species.
Also, all species may not require to be treated for all the stages.
It
is of utmost importance to identify the mother plants carefully as
micropropagation techniques do not bring any improvement in the genetic
make-up of the plant and only produce mirror images of the selected
mother plant.
Further,
as the plants grow in the field, they are exposed to a large number
of microbial contaminants and thus harbour a large number of micro-organisms
on their surface and sometimes also have a high level of endogenous
bacteria, yeast-like microorganisms, fungi, and virus.
In
these instances, the mother plants are prepared for raising aseptic
cultures and various techniques for rejuvenating the material such
as pollarding and coppicing are attempted.
Growing
cuttings in the green house or covering them with poly-bags or spraying
them with fungicides are some other parameters used for preparing
mother plants for raising aseptic cultures. Explants are then sterilised
to ensure removal of microbial contamination by treating with chemicals
and then put on the sterilised growth medium.
The
growth medium typically contains the energy source, major and minor
salts, vitamins and growth regulators required to stimulate growth
in the explant.
The
most common method of shoot multiplication for cloning is through
the enhanced axillary method. The axillary bud found in the axil of
each leaf has the potential to develop into a shoot. In normal conditions
these buds remain dormant but if the terminal bud is injured, the
next axillary sprout takes over the role of the terminal bud. This
phenomenon is controlled by the interplay of growth regulators.
The
excised nodal explants, thus, when provided with appropriate conditions
for the growth of the shoot, show sprouting of axillary buds. Depending
on the species, it can be either a single shoot or a cluster of shoots,
which can be separated every three weeks for further multiplication.
Once enough shoots are formed, they are put for rooting.
Although
plants propagated through tissue culture appear to be green in colour,
they are neither capable of efficient photosynthesis nor are they
equipped with a proper mechanism to control
contd...
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