Transgenes from GM crops can end up in wild relatives of these crops via crossing. But the chances of this happening very much depend on where in the genome of the plant the new gene is introduced, according to research at Plant Breeding.
Wageningen trainee research assistant Brigitte Uwimana tested this by crossing cultivated and wild lettuce varieties and then crossing their offspring several times with wild lettuce varieties. She then used markers to find out which DNA fragments of the cultivated lettuce ended up in the genome of the wild lettuce. 'This is because a gene cannot get into other varieties on its own,' says her supervisor Rene Smulders. 'It is always found in a piece of genome.'
If that piece of genome wants to remain in the genome of the wild lettuce, there must be a fitness advantage. For example, the crossing grows faster or produces more seeds than the wild variety. The genome analysis showed that some pieces of genome raised this fitness and other pieces of genome were edged out in de selection process. Therefore, to produce a safe GM lettuce requires introducing the gene in those parts of the genome which lower the fitness in wild varieties, says Smulders. In this way, the chances of 'leakage' of such genes into the environment can be minimized.
The test using the lettuce - not a GM crop - has shown that 'strong' and 'weak' spots can be pinpointed in the genome, so that these can be taken into account during genetic modification, says Smulders. This information is of great importance to the Netherlands Commission on Genetic Modification (COGEM), the government's adviser on the risks of GMOs. Whether this knowledge will be applied in breeding, Smulders does not know. 'COGEM will need to assess how big the extra safety benefits are, while breeders have to find out whether such benefits are easy to achieve and to weigh these against the costs.' He will publish the proceedings of the research, funded by NWO, in this month's Theoretical and Applied Genetics.