A crop with in-built protection that can fight back against its main pest would seem a 'holy grail' for agricultural industries.

Cotton is the first of Australia's agricultural commodity industries to commercialise a genetically-modified (GM) crop ó 'Ingard' varieties of cotton ó putting the dream to a large-scale test. Getting the crop into the field has required the skills of conventional plant breeders as well as genetic engineers.

Ingard cotton has been modified to include a gene from the soil organism Bacillus thuringiensis (Bt). By including the Bt gene, science has created a cotton plant which produces a protein toxic to Helicoverpa larvae (a type of caterpillar).

The protein produced in Ingard plants is a specific pesticide against key pests, particularly Helicoverpa, and does not affect other insects or organisms. The oil from Ingard cotton seed is genetically indistinguishable from other cottonseed oil (oil contains no protein).

Reduced pesticide use

After three seasons of Ingard in the field, the benefits are clear. Average use of chemical pesticides on transgenic cotton was 38% less in 1998-99 (a year of exceptionally high insect pressure), 44% in 1997-98 and 52% in 1996-97 when the technology was introduced to the market. (Source: The Performance of Ingard Cotton in Australia during the 1998-99 Season, Cotton Research and Development Corporation).

Economic benefits for growers from the new technology have been variable but generally only small when compared to conventional cotton, so it is the environmental benefits that are continuing to drive the technology's introduction and expansion.

Regulations

Far from being a haphazard process, producing a successful transgenic crop can take more than 10 years and is scrutinised by several regulatory bodies along the way.

The first step in developing a transgenic crop is identifying a donor organism within which a desired genetic trait occurs. In Australia and internationally, formulations based on various strains of the Bt soil bacteria have been used for decades as highly specific natural pesticides and have been popular with organic growers and home gardeners. This meant there was an enormous amount of scientific data available on the efficacy and effects of the pesticide.

Once a donor organism has been found, science steps in to isolate the specific desired gene from the DNA sequence. And because plant genes use different control signals to animals or bacteria, it is necessary to swap the signal section of the gene with an appropriate 'promoter' from a donor plant. Constructing a new gene in this way gives scientists precise control over when and where the new genes will be expressed within transgenic plant.

When the gene is in a form ready to go to work, it needs to be introduced into the plant's chromosomes. In the case of cotton, researchers turned to a plant tumour disease caused by a soil-borne bacterial pathogen. The disease was caused when the pathogen transferred some of its genetic material into the DNA of the infected plant ó a form of 'natural genetic engineering'. By replacing the bacterium's disease-causing genes with potentially useful constructed ones, the bacterium can be used to transfer material from the test tube into plant cells.

From here a good tissue culture system allows the regeneration of whole plants containing the new genes which can be grown to harvest for seed collection. The time frame for transformation and regeneration is between 10 and 18 months.

Testing

When the seed becomes available for breeders, the transformed lines are crossed and backcrossed into commercial varieties. While the transformation process confers the genetic trait, conventional breeding makes sure the plant is adapted to local conditions and is fundamental to providing the best varieties to farmers. The backcrossing, testing and eventual development of foundation seed stocks can take five years or more.

During this time testing continues to ensure the plants are effective against the target pests, and pose no risk to human, animal or environmental health and safety.

In the case of Ingard cotton, the Genetic Manipulation Advisory Committee controlled pre-registration developments and studies, such as issues surrounding the release of genetically-modified organisms into the environment.

Local research has shown there is no chance of transgenic cotton pollinating wild cotton and no possibility of widespread movement of pollen to other cotton.

The National Registration Authority then considered varieties containing the Ingard gene as they would any new pesticide. Ingard is available to farmers through a contractual agreement with the technology's owners, Monsanto. This contract conforms to aspects defined by the Authority's labelling requirements including measures designed to prevent the development of pest resistance. The Australia New Zealand Food Authority also plays an important role in ensuring the wholesomeness of food derived from the cotton plant (for example, oil) and subsequent labelling requirements.

Only when all the conditions are met can the transgenic product reach the market, but this is not where the hard work stops.

Management strategies have been developed and imposed for Ingard cotton to ensure pest resistance is delayed or prevented for as long as possible. By developing effective products under the proper regulatory controls, with strategies designed to maintain the efficacy of those products, Australian agriculture can look forward to an internationally-competitive and environmentally-sustainable future.

Contact: Tim Lester, Communications Manager, CRDC, (02) 6792 4088, email: timlester@mpx.com.au