Environmental Safety Out-crossing and Gene Flow

Interbreeding between cultivated plants and their wild relatives is constantly taking place. The fact that transgenic plants are no exception to this has aroused suspicion among critics. The questions of if and when this could happen have been a focus of environmental safety research for quite some time. Lately, the essential questions are being revised. The more pressing, practical concern is: does the passing on of the new gene pose a real threat?

Out-crossing does not necessarily mean environmental damage. Whether or not the environment is at risk is a question being addressed by researchers. For example, does a new gene confer some kind of fitness advantage? If so, the possibility that the new gene could enable a plant to get an unfair advantage in nature needs to be thoroughly investigated. In other scenarios, a gene from a GM plant could make its way into nature, possibly putting that plant at a disadvantage.

Rapeseed: Out-crossing is possible, but what would the consequences be?

Based on these concerns, environmental safety research addresses: If the new gene could be passed on to other plants, and if so: If the trait associated with the new gene could have ecological consequences. If there are adequate safeguards against gene flow between the GMOs and native organisms when transgenes could affect fitness, decrease genetic diversity, or increase toxicity.

Management strategies could include avoiding the planting of transgenic crops in their centres of biodiversity. Genetic engineering can be used to alter flowering periods to prevent cross-pollination, to ensure that the transgenes are not incorporated in pollen, and to induce sterility.

When can out-crossing take place?

Out-crossing oftransgenes is possible when compatible hybridisation partners are found nearby. The most common way of out-crossing is the dispersal of pollen to sexually compatible plants. This can occur by:

• The transfer from crop genes to wild relatives (e.g., rapeseed to turnip rape)
• The exchange of genes between or among crops (e.g., sugar beet to garden or fodder beet, or maize to maize)

Organisms of the same species can interbreed with each other. Although breeding compatibility is a definition of a species, these boundaries are not absolutely strict. This is made obvious by the multitude of hybrids that exist between different species (interspecific hybrids). In plant breeding and in agriculture, the ability of plants to breed between and among species allows for the movement of genes among crops and between crops and wild relatives.

In certain cases, crops may interact with related wild plants forming crop-weed complexes (sugar beet and sea beet). These weed populations can act as reservoirs of foreign genes, potentially including genes introduced by genetic engineering. These weed populations can also act as bridges, allowing gene flow between crops and wild species that are usually unable to interbreed.

See also on GMO-Compass:

• Which crops could spread their genes?