Concerns about GM herbicide tolerance

People who are concerned about using plants genetically modified for herbicide tolerance are generally worried that:

  • the plants will 'escape' into the natural environment and become a problem,
  • the plants will interbreed with other plants in the environment and produce 'super-weeds' that are resistant to a number of herbicides, and
  • there will be a transfer of the gene to non-GM and organic crops.

Plants may escape if their pollen or seeds are taken or are blown outside the paddock or farm.

Pollen is carried by the wind, insects or other animals. Farmers have no control over where the pollen from their plants ends up. However, it is possible to change the pollen-making genes in a plant so that the plant produces no pollen, or pollen that is not able to produce seeds - the latter would not work well for crops where we use the seeds, such as canola.

One technique that is being considered is the insertion of genes into the plants' chloroplasts. Chloroplasts are structures that contain the plants' green pigment, and lie outside the nucleus. Because chloroplasts are not within the nucleus, they are not passed on in pollen and, as a result, the GM plants cannot exchange their inserted genes with other plants and make weeds that are difficult to control with herbicide.

The most commonly used crop plants are hybrids (crossbred). Hybrids generally produce seed that can germinate, but the resulting plants will not have the same vigour as the parent and so are unlikely to survive for long.

However, if the plants do 'escape', they will only survive and become a potential problem if they have properties that enable them to compete successfully with plants already in the natural environment. French researchers have claimed that there is a greater risk of GM plants escaping into the wild from GM seeds being left in the fields than GM pollen being blown away from crops.

To read some of the recent news stories surrounding this debate, go to New Scientist:http://www.newscientist.com/channel/opinion/gm-food/