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TECHNOLOGY
Super crops become a back paddock reality
by Nicole Baxter,
KONDININ GROUP
G
enetic engineering is a rapid way of
modifying plants and animals which
could revolutionise the way primary producers
approach farming in the future.
This breeding method is expected to provide
farmers with speedy access to new high
yielding, high quality crop varieties resistant
to insects, weeds and diseases.
It could also open up millions of hectares of
infertile land to profitable crop production and
help meet the food demands of a growing
world population.
Despite the potential benefits of genetic
engineering, no foods bred using this
technology have been released to Australian
consumers.
But in the United States of America and the
United Kingdom consumers have already
sampled tomatoes with longer shelf lives and
several more genetically engineered foods are
to be released in the near future.
Genetic engineering is the term used to
describe the process of taking a gene from one
organism and transferring into another.
The process is not new. For more than one
thousand years scientists have created crops
with new agronomic traits by cross-breeding
them with plants from a related species.
But cross-breeding usually takes 8-10 years
to produce varieties for release to farmers
while genetically engineered plants can be
released after about 4-5 years.
Another advantage of genetic engineering is
that plant breeders are not limited to working
with characteristics that already exist in
particular crops - a desirable characteristic
from an unrelated organism can be transferred
into a plant. The main aim of genetic
engineering is to change the characteristics of
a plant or animal by making its cells perform a
FIGURE 1 Gene gun technology
Helium
Particle gun
Solenoid
Timer
DNA-coated
particles on
mesh
Vacuum
chamber
Protective
screen
Target cells
CSIRO
Vacuum
FARMING AHEAD No. 55 - July 1996
A relatively new tool has been developed
and used to genetically engineer grass
plants.
The tool consists of a particle gun which
can directly “shoot” minute gold or
tungsten beads coated with pieces of DNA
directly into plant cells. A high pressure
blast of helium is used to accelerate the
beads from a mesh screen into the plate of
target cells below. These beads lodge
inside the cells and release their DNA
coating.
Scientists identify portions of the tissue
which carry the additional DNA and the
tissue is then selected and grown to
maturity.
As with other genetically modified plants
the seed will always bear the additional
DNA and plants grown from these seeds
may display the desired trait.
Centre for Legumes in Mediterranean Agriculture
researcher Dr Penny Smith showing the first
genetically transformed lupins to Western
Australian farmers Wally and Linley Filmer.
specific task in a predictable and controllable
way. This may involve making lupins
resistant to the disease cucumber mosaic virus
(CMV) or modifying tomatoes so they last
longer on the shelf.
Gene research in agricultural plants is
mainly in two areas. The first area involves
production characteristics such as insect, virus,
fungus and herbicide resistance.
For example, there is presently no known
control measures for plant viruses like
CMV and bean yellow mosaic virus (BYMV).
These affect many crops and the only way to
significantly limit losses is by killing the
insects which transmit the disease.
Researchers in Australia are working to
develop a lupin plant with resistance to these
two diseases.
Field trials in Australia and the US have
confirmed that plants with resistance to these
diseases will be effective in the agricultural
environment, saving farmers millions in lost
production and control measures.
The second area for genetic engineering
research is the improvement of quality
characteristics like increased oil content in
canola and different protein contents for wheat
varieties.
Genes
Any improvement to a plant’s yield or
quality is made by changing the instructions
contained in the plant’s genes.
Genes are the chemical messages or codes
within cells which determine the look of the
plant and how each part functions.
These messages are based on a substance
called deoxyribonucleic acid (DNA). DNA is
made of four chemical building blocks which
are arranged in pairs and look like a spiral
staircase when viewed under a high powered
microscope (see Figure 2).
Millions of different combinations of these
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TECHNOLOGY
Genetic engineering...
four chemical building blocks determine the
way every organism looks and works.
Genetic engineering allows scientists to add
or remove parts of these building blocks to
improve plants, animals or micro organisms.
Before organisms are genetically
engineered, scientists need to find a useful
gene which can be added to single cells before
being grown into a whole plant.
For example, one promising development is
the discovery of a gene which detoxifies the
herbicide Basta.
This gene has been cloned from the
bacterium Streptomyces hygroscopicus. When
it is inserted into plants it produces a high
level of tolerance to Basta.
Basta-resistant lupins are being tested in
Australia this year and will be made available
to growers in about four years’ time. This will
allow growers to spray lupins with Basta to
kill weeds without damaging the crop.
Introducing DNA
To introduce a permanent genetic change
into an animal, a gene must be directly
inserted into the nucleus of a fertilised egg.
The new genes are injected using a
microscopic needle and a device called a
micro-manipulator which is used to hold the
receiving cell in place. If the egg survives the
insertion and withdrawal of the needle, it is
implanted into the uterus of a mother animal.
It is more difficult to introduce DNA into
plant cells because they are surrounded by a
strong box-like wall which is not easily
penetrated.
To overcome this scientists use microbes
which infect plant cells with their own DNA.
The new piece of DNA is placed in the
FIGURE 2 How plants are genetically engineered
Gene
The benefits
1. Identify a gene
(from any organism) encoding desirable
protein, for example, the coat protein that
encapsulates a particular virus.
DNA
2. Build a new gene from
genetically different tissues
from assorted pieces of DNA, including the
coding sequence of the desired gene.
Agrobacterium
Transferred DNA
3. Introduce gene into vector
such as the tumour-inducing plasmid (Ti) from
Agrobacterium tumefaciens, which infects
plants and causes crown galls.
Chromosome
Tumour-inducing
plasmid
4. Transfer the gene
by infecting plant cells with the bacterium.
When cells encounter the Ti plasmid containing
the new gene they incorporate the new
genetic material into their own.
Plant cell wall
Nucleus
Chromosome
Cloned cells
5. Regenerate whole plants
Select plants which contain the new genetic
material, clone them and generate whole
plants using tissue culture techniques.
6. Test the transgenic plants
New Scientist
Evaluate whether the new gene is active and
how well the plant will resist viral infection
and hold field tests.
7. Breed a hardy plant
Using conventional plant breeding, make additional
crosses with other crop varieties to develop a hybrid
that farmers can successfully grow.
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bacterium which acts like a courier, carrying
the introduced DNA into the plant cell (see
Figure 2). In the case of lupins, gene transfer is
achieved by infecting the growing tip with a
bacteria which transfers the gene to the plant’s
cells.
Scientists wound the growing tip and apply
a bacterial solution containing the new gene.
After infection has occurred, shoots which
develop on the seedling are transferred to a
nutrient gel containing everything required for
plant growth.
The gel also contains antibiotics or
herbicides which kill any remaining bacteria
and identify the genetically engineered shoots.
When these plants produce seeds, the new
seeds may contain the additional DNA.
Plants such as tomatoes, tobacco, soybeans,
lupins and lentils are modified using this
method. Gene gun technology and
electroporation are used to modify grass crops
such as corn or wheat and rice (see Figures 1
and 3).
Plant with new traits
Genetically engineered plants have the
potential to take agriculture in a new direction
which will benefit farmers, marketers, retailers
and consumers.
For farmers, genetically engineered plants
could decrease costs and reduce the need for
chemicals while lifting crop yields beyond
current levels.
For example, herbicide use is increasing
rapidly in Australia and plant resistance to
selective herbicides has placed added pressure
on continuous cropping systems.
Genetic engineering is creating new plants
which are tolerant to herbicides, giving
farmers new options for controlling weeds in
the non-cereal phase of their rotations.
Scientists are working on producing a
Basta-resistant lentil. Lentil production is
increasing rapidly in Australia yet their early
growth is slow and they are susceptible to
early weed competition. New genes can be
easily introduced into lentil plants using
bacteria carriers.
Bacterial genes have also been used to
detoxify the herbicide 2,4-D and bromoxynil.
Work by Monsanto is giving plants such as
canola resistance to the herbicide Roundup.
The company has also developed a cotton
variety with in-built resistance to heliothis
caterpillars. The variety is being trialled for
release to farmers next year.
For the food processing and marketing
industries, new genes will decrease transport
spoilage, reduce the time to market products,
guarantee a consistent supply of food and
provide a wider range of higher quality
products.
For example, researchers are working to
modify the starch content in wheat to produce
a much higher fibre content in white bread
which is consumed by many Australian
children.
The protein content of wheat grain will also
FARMING AHEAD No. 55 - July 1996
Safety concerns
Consumer demand for healthy foods is
increasing and some people are concerned
genetically engineered products may not be
safe to eat.
While concern about eating plants with
genes not fit for human consumption is
justified, humans have eaten plant and animal
DNA for millions of years and the introduced
DNA is no different from its original source.
Researchers believe altered DNA will not
cause health problems if the introduced gene is
eaten in other food sources.
Another concern is that genetic engineering
will make some species dangerous pests or a
threat to life.
Many organisms, including the rabbit,
prickly pear and cane toad, have been
introduced to Australia without adequate
assessment of their likely impact on the
environment.
But the only valid threat posed to the
environment by genetically engineered plants
is that they could give rise to weeds.
A problem could occur if genetically
modified plants began to invade nonagricultural locations. For example, a crop
which was altered to improve its waterlogging
tolerance may out-compete wild plants.
Perhaps a greater threat is that genes from
genetically engineered crops could be
transferred to existing weeds through pollen.
For example, a gene for herbicide tolerance in
canola could quickly cross into the wild radish
population.
Although super-weeds and volunteer weeds
could result, control would be still possible
provided there was no cross resistance to other
herbicides.
Scientists cannot be certain modified
organisms will behave in a certain way but all
genetically modified plants are extensively
trialled before they are released. Each stage in
the breeding process is monitored closely so
the work can be stopped if a problem occurs.
Ethical concerns
There are a number of ethical concerns
which will also determine the success or
failure of genetically modified organisms.
One concern is that multinational chemical
companies are using genetically engineered
FARMING AHEAD No. 55 - July 1996
FIGURE 3 Electroporation
Some protoplasts recover,
regrow a cell wall and express
the foreign DNA
Protoplast
and foreign
DNA
Culture for seven days
Electrical charge
Pores open briefly in
protoplast membrane
CSIRO
be changed while farmers may soon see the
development of specific wheats, each with a
protein content suited to a particular market.
If the genes that code for the nitrogen-fixing
system of certain bacteria could be added to
crop plants, the world’s food production would
dramatically increase and nitrogenous
fertilisers may become unnecessary.
Genetic engineering would also multiply
food production by reducing losses caused by
pests and diseases which currently claim one
third of the world’s crops. But these
advantages will amount to nothing if
genetically modified plants fail to be accepted
by the consumer.
TECHNOLOGY
Genetic engineering...
Electroporation is another method of transferring genes from one organism to another. This
process involves submerging protoplasts (cells which have had their walls removed) in a solution
containing the new DNA and applying a brief high-voltage electrical charge. The electrical pulse
causes temporary breakdown of the plant’s cell walls, allowing entry of the new DNA. Newer
electroporation methods use whole plants. Crops including rice, lucerne, tomato, potato and
canola can be modified using this method.
herbicide resistant crops as a ploy to secure
customers for their chemicals and seed.
Although these concerns could be valid,
questionable marketing efforts are not
restricted to gene technologies and issues like
these have to be dealt with by regulation and
customer rejection. The moral issues
surrounding genetic engineering are huge.
Some people believe manipulating genes is
“playing God” and “interfering with nature”.
Others are more concerned about whether
including animal genes into plants makes the
new plant unsuitable for vegetarians.
Likewise, Jewish people may object to
genetic engineering if genes from pigs were
used in plants or animals which were once
deemed acceptable.
Another moral issue to consider is the
impact of gene technology on farmers
overseas. Genetic engineering has the
capacity to ruin the economies of many underdeveloped countries heavily reliant on
supplying crops to the industrial world.
A hypothetical example of this is a
genetically modified wheat plant that produces
latex. What would be our responsibility
towards overseas producers?
Although it is easy to argue farmers in
developing countries who cannot afford
chemicals would benefit from sturdier crops,
the question remains as to whether the seed for
such crops will be affordable.
Despite the fact that tomorrow’s farmers
could have greater pest control options and
higher crop yields, any savings may be passed
directly onto consumers.
Farmers may end up paying a high price for
crops that offer no real advantage over existing
pesticides. For example, insects can adapt to
built-in defences as they do to chemicals, so
genetically modified crops may have to be
continuously re-engineered.
For commercial companies, it may not be
worth spending the money to develop a new
crop variety if it is likely resistance will
develop. Despite some major achievements,
genetic engineering still has a long way to go.
Adding herbicide resistance genes to plants
has been an early success story because single
genes are used to control the production of an
enzyme which is able to degrade the herbicide
and render the plant resistant.
But a multitude of factors, each one
controlled by up to several hundred genes,
govern yield and plant productivity.
Yield can be improved but only through
modifications of plant characteristics under the
control of more than a few genes.
A combination of genes are required to
change factors like nitrogen fixation, disease
resistance and crop quality. The modification
of such complex processes will require much
time and dedication.
Regulation
Genetic engineering research in Australia is
regulated by guidelines developed by a
government appointed committee known as
the Genetic Manipulation Advisory Committee
(GMAC).
The committee oversees all stages of a
project from approval to release. It is
concerned with risk factors associated with a
genetically modified organism which may give
rise to safety concerns in public health,
agricultural production and the quality of the
environment.
Since 1988 there have been 22 requests for
releases of genetically modified organisms in
Australia of which seven have involved the
small-scale field testing of modified plants
including:
• Virus-resistant potatoes
• High yielding canola
• Delayed ripening tomatoes
• Longer vase life carnations
• High yielding potatoes
• Insect resistant cotton.
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