Understanding Biotechnology

What is Biotechnology

Overview of Biotechnology

History of Biotechnology

Why do we do biotechnology?

Biotechnology for the environment

Biotechnology for food and agriculture

Increased pressure from importing countries, changing Australian regulations covering farm safety, environmental degradation and pesticide residues are pushing farmers and researchers to find and adopt more sophisticated integrated pest management practices.

What is cotton?

When the bud has flowered, it turns pink and the petals fall off. Seeds are then formed in a small green pod called the cotton boll.

Huge numbers of seed hairs form around each seed and these white fibres become packed around the seed inside the boll. When the boll is mature, it bursts open, showing the soft cotton fibres, which help the cotton seeds spread.

Cotton fibres are about 2 to 4 centimetres in length. They are made up of about 87–90 per cent cellulose. This is a tough carbohydrate molecule that makes up the cell wall of all plants. The fibres also contain 5–8 per cent water and about 5 per cent other substances.

The length of the cotton fibre determines the quality, and therefore the price, of the cotton produced. The longest fibres are woven into the highest quality cotton fabric.

Why do we grow cotton?

Cotton is seen as a natural fibre that is versatile, comfortable, desirable and extremely useful. Cotton can be as fine as a handkerchief or thick like denim. It can be dyed to be any colour you like, easily washed and dried, and added to other fibres for functional clothes and other uses.

The Australian cotton industry produced 1.65 million bales of cotton in the 2002/03 season. This was less than a ‘normal’ cotton season (a reduction of over half) due to the drought.

That year, the world cotton industry produced about 84 million bales. Of this, China produced 21.5 million bales and the USA produced 19.5 million bales. Other major producers include India, Pakistan and Uzbekistan.

Australia exports over 96 per cent of its cotton crop. In a normal year, the value of these exports is in excess of $1.5 billion. The main buyers of Australian cotton are Indonesia, South Korea, Japan and Thailand.

Maintaining our market share means continually looking for improved farming practices. Managing insect pests is a major issue.

What’s the problem with insects?

Cotton growers have previously relied heavily on applications of broad spectrum pesticides to control insect pests. In the past few years, they have moved more toward integrated pest management, where predatory or ‘beneficial’ insects are encouraged onto the farm to provide a level of natural control of the pest species.

Additional crop areas, called trap crops or refuge crops, are planted to move pest insects away from the cotton and to increase the number of beneficial insects in the area.

Less harmful, more selective chemical pesticides are used if necessary, and researchers continue to focus on the management techniques offered by transgenic cotton crops.

Australia's worst cotton pest is Helicoverpa armigera, a type of cotton bollworm.

The adult of this pest is a moth that lays its eggs on cotton plants. When the caterpillar (larvae) hatches, it starts eating the food around it – the cotton plant. The caterpillar then burrows into the cotton seedpod (boll) to find more food, and in the process damages the cotton. The caterpillar is called the cotton bollworm or cotton boll weevil.

When the larvae have grown, they crawl down the stem of the plant into the soil. Here they turn into pupae, inside a hard case. The pupae metamorphose (change) into the adult moth stage in the soil. Four or five generations of these moths can be produced each year.

Cotton is also attacked by several hundred other species of insects. The cotton leafworm, cotton fleahopper, cotton aphid, rapid plant bug, cochineal bugs, southern green stinkbug, spider mites, grasshoppers, thrips, and tarnished plant bugs all feed on various parts of cotton plants. Because of the large number of insect cotton pests, repeated spraying of insecticides is needed throughout the growing season.

Using insecticides to kill insect pests

This use of insecticides raises a number of concerns:

• Insects can rapidly become resistant to insecticides.
• Insecticides can kill other types of insects as well as the pest species.
• Insecticides often kill other beneficial insects that prey on the pest species, thus destroying a natural way of controlling the pest.
• Birds that eat insects killed by the chemicals can become sick, possibly endangering some bird species.
• Some insecticides are dangerous to people living and working in the cotton growing areas.
• Nearby waterways can be contaminated by insecticide run-off.
• Although today's chemical insecticides are much safer than in the past, they can still cause problems for human health

Using viruses and venoms to kill insect pests

Baculoviruses, which specialise in infecting the caterpillars of many moth and butterfly species, can be used to control caterpillar pests. Scientists in the USA have genetically modified a virus that is intended to control cotton caterpillars. Scientists in Australia are considering importing these experimental baculoviruses for laboratory trials.

The GM baculoviruses contain a gene for a type of scorpion venom. When the baculovirus infects the caterpillar, it invades the caterpillar's cells. The cells take up the gene for scorpion venom and begin to produce it. The venom paralyses the caterpillar, in the same way that a scorpion sting would do. As a result, the caterpillar dies within 36 hours.

Before considering the release of these baculoviruses in Australia, scientists conducted a trial to see how the baculovirus behaved in Australian conditions - whether it infected non-target insects and competed with Australian baculoviruses.

Researcher Andy Richards (from CSIRO Entomology) concluded:

“The results show that the question of how a GM virus might interact with the cotton agro-ecosystem is more complicated than was originally thought. Further research is necessary before GM viruses can be widely used in this country and this work is important because it provides a focus for future investigations to better judge potential risks to the Australian environment.”

A biotechnology solution to insect pests in the case of cotton

By the early 1990s, the cotton bollworm had developed resistance to most chemical pesticides. Scientists working for the United States company Monsanto developed a cotton variety called Ingard®, which contains a gene derived from the Bt bacterium.

When the gene is inserted into cotton plants, they produce toxic proteins called Bt toxins that kill the bollworm caterpillars. The poison stays in the leaves and does no harm until the bollworm eats the leaf tissue. It is very specific — it only kills bollworm caterpillars and very closely related species. It does not affect humans or other animals.

In the 1990s, CSIRO Plant Industry scientists used licensed Monsanto genes to develop Bt cotton varieties that were suitable for Australian conditions. This variety was called Ingard® cotton.

In 1999, about 40 million hectares of GM Bt cotton were planted worldwide. In the same year, about one third of Australia 's cotton crop (100,000 hectares) was Bt cotton.

Some bollworm caterpillars may be resistant to Bt, which means that Bt cotton crops still need to be sprayed with insecticides to kill any surviving caterpillars. However, the introduction of Ingard® cotton greatly reduced the amount of insecticide spray used on cotton crops.

The CSIRO has since created a new form of Bt cotton, known as Bollgard®II, which also uses licensed Monsanto genes. Bollgard®II is Ingard® cotton with an additional different Bt insecticidal gene. Having two genes significantly reduces the possibility of the bollworm developing resistance to the Bt toxins.

Bollgard®II cotton has reduced pesticide use in Australia by up to 80 per cent compared to conventional varieties.

Concerns about insecticide resistance

The problem is that an insecticide never kills all of its intended victims. If even a few insects survive, they will reproduce. They will produce two types of young - those that are resistant to the spray, and those that are not.

The non-resistant insects will be killed in the next spraying, but those that are left reproduce. At each generation, the number of naturally resistant insects in the population increases.

An individual insect does not become resistant during its lifetime. It is born either resistant or non-resistant, and it is the population as a whole that gradually becomes resistant to the pesticide over time. The Bt toxins become ineffective, and the benefits of using them (less toxicity to non-target species) disappear.

As this occurs, a new pesticide must be developed. Over time, populations of insects can become resistant to more and more pesticides. As a result, humans need to make different pesticides that are generally stronger.

Organic farmers have used Bt on their crops for a number of years. They are concerned that the increased use of the Bt toxin could speed up the development of resistant insect populations.

Entomologists know that controlled, laboratory experiments with generations of insects can not be easily reproduced in the field. How the resistant insects breed with refuge insects, and over what time frames, will determine the success of this technology.

These concerns are balanced by concerns that existing pesticide practices can be much more dangerous for non-target insect species than insect-resistant crops. Conventional non-selective pesticides kill many non-target insects. By reducing the number of sprays needed, insect-resistant crops help to preserve beneficial predator insects and simplify management decisions.

Controlling insecticide resistance

Two solutions to this problem are being investigated.

Double the genetic punch

One solution is the 'double and triple whammy'. This involves genetically modifying the plant by adding two or three insecticide genes, so that two or three toxins are produced. If an insect becomes resistant to one toxin, the other will still kill them. The number of bollworms that will be resistant to genetically modified plants with two or three different insecticide genes will be very small, and arise only rarely.

Bollgard®II is an example of the 'double whammy' principle at work. It uses two different Bt insecticide genes to deliver insecticides to the insect.

Reduce the chance of finding a resistant mate

The second solution involves refuges, which are areas of land near the crop planted with non-GM cotton. Farmers are not allowed to spray the plants in the refuges.

The bollworm moths will be able to grow and breed safely in the refuges and the population of moths that are not resistant to any pesticide will remain high. These non-resistant moths will be able to breed with the moths that have become resistant to the GM cotton.

The eggs and caterpillars that are produced will probably not all be resistant to the insecticide. These caterpillars will be killed when they eat the GM cotton. However, there will still be moths thriving and laying eggs in the refuges. This will ensure that the numbers of non-resistant moths remain high, and that the environmental benefit of using Bt instead of more toxic synthetic insecticides is not threatened.

The current Australian regulations prescribe that up to 90 per cent of a cotton crop can be planted with Bollgard®II on any one farm. This may be lifted to 100 per cent if other crops such as pigeon peas are planted as refuge crops to slow down the emergence of Bt resistance in cotton bollworms.