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Gene flow comes under scrutiny

GM oilseed rape genes may cross out into other plants (www.nature.com) swissinfo.ch

Scientists from around the world are meeting in Amsterdam this week to discuss how genes from genetically modified crops cross over into wild plants.

This content was published on January 22, 2003 - 11:12

They will present the latest research on gene flow and discuss its environmental and evolutionary impact.

Among the participants is Klaus Ammann, director of the botanical garden of Bern University.

In 2002, genetically modified plants were grown on more than 58 million hectares worldwide, an area bigger than Germany, the Netherlands and Belgium combined.

The conference will start by looking at how conventional crops have transferred genes to their wild relatives.

This process, which generally does not cause any public concern, offers a benchmark for comparing the behaviour of genetically modified plants.

"There are so many plants hybridising or 'crossing out' and they did that long before genetic engineering was developed," Ammann told swissinfo.

"A lot of opponents of genetic engineering behave as if pollen only learnt to fly with transgenes - the genes that are artificially put into the plants - but plants have always hybridised."

Gene flow

Ammann said that in 99 per cent of cases, gene flow does not have any negative consequences.

However, he said it was wise to take precautionary measures because in the future new genes might cause some competitive advantage.

"There is a possibility that a gene comes into another plant which makes it more competitive. This other plant could be a weed, related to the crop, and this weed would become more competitive and a bigger problem for farmers."

Ammann said there were no known cases so far. "Even in oilseed rape, the problems are under control despite the fact that transgenic oilseed rape has crossed out," he said.

Seed dispersal

Ammann and his team use collections of dried plants to study the effects of hybridisation.

Hybrids are normally very well represented in these collections and allow scientists to compare over decades what has happened in the field.

Scientists use three criteria to assess the risk of gene flow: the frequency of a plant and its relatives; how its pollen is transported by wind or bees; and the way its seed is distributed.

"There are big differences in frequency, hybridisation and seed dispersal," explained Ammann.

"When you have very common wild relatives, the likelihood of getting hybrids is much higher.

"Grasses have a high potential of producing hybrids, and on the other hand you have potatoes which have a very low potential."

Transgenic plants

There are currently no transgenic plants grown in Switzerland.

Ammann said maize, which carries a transgene, should not be planted in Switzerland as long as it can cross out.

"Maize can hybridise over hundreds of metres to other plants of maize and then it might happen that you have an unwelcome mixture. In Swiss agriculture, with its small structured fields, this situation is particularly difficult."

"But I oppose the view that all transgenic crops are highly risky regarding gene flow. You could easily plant transgenic potatoes in Switzerland without any risk."

Legal challenge

Participants from science, plant breeding, governmental regulatory institutions, and policymakers have registered for the meeting which is organised by the European Science Foundation.

Genetically modified seed has been re-engineered to add characteristics that, for example, add vitamins or make the plant more resistant to pests.

The United States, Argentina, Canada and China continue to be the leading growers of GM crops.

Last week the US government's top trade official threatened to take the European Union to court over Brussels' refusal to import genetically modified crops.

The EU has banned the approval of any new genetically modified crops since 1998 because of public disquiet about potential risks to health and the environment.

swissinfo, Vincent Landon

Key facts

The conference is being organised by the European Science Foundation and will focus on how genes from genetically modified crops cross over to wild plants.
In 2002, GM plants were grown on more than 58 million hectares worldwide.
The United States, Argentina, Canada and China are the leading growers of GM crops.
The EU has banned the approval of any new genetically modified crops since 1998 because of public disquiet about potential risks.

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