Interaction with the environment

Potential for weediness?

Two main concerns about potential environmental impacts remain the focus of public attention. These are, the possibility of a genetically modified crop becoming a weed, and the possibility of unwanted genes being transferred to wild relatives. Plants possess varying degrees of quantifiable inherent weedy behaviour. Thus, the effect of a transgene on weediness will be mainly a function of the new genetic background into which it is introduced. Weeds are mainly an agricultural problem and not an environmental one, requiring adequate management practices in the field to be dealt with. The other main concern is with the displacement of related plants in the wild or the introgression of transgenes into those wild relatives, principally in centres of origin. One of the questions being debated is whether the introgression of a transgene into wild relatives could cause loss of biodiversity at all or be different in any way from traditionally bred commercial varieties.

Rice paddies harbour a plethora of organisms, including algae, microorganisms, beneficial insects, and sometimes commercially utilised crayfish. To maintain this diversity it is important to develop agronomical practices that minimise the use of biocidal compounds.The use of resistance genes, crossed in from other varieties or introduced by genetic engineering, eg Bt genes, is one way of managing threats to both the crop and the environment.

Below is a list of papers that deals with introgression of transgenes in centres of origin:

• Celis C, Scurrah M, Cowgill S, Chumbiauca S, Green J, Franco J, Main G, Kiezebrink D, Visser RGF & Atkinson HG (2004) Environmental biosafety and transgenic potato in a centre of diversity for this crop. Nature 432:222-225.
• Ming High S, Cohen MB, Yao Shy Q, Altosaar I (2004) Achieving successful deployment of Bt rice. Trends in Plant Science 9:286-292.
• Nap J-P, Metz PLJ, Escaler M, Conner AJ (2003) The release of genetically modified crops into the environment. The Plant Journal 33:1-18.
• Stewart CN Jr, Halfhill MD, Warwick SI (2003) Transgene introgression from genetically modified crops to their wild relatives. Nature Reviews 4:806-817.