Genetically modified (GM) cotton genes have been found in wild populations for the first time, making it the third plant species — after Brassica and bentgrass  — in which transgenes have established in the wild.

The discovery was made in Mexico by six Mexican researchers investigating the flow of genes to wild cotton populations of the species Gossypium hirsutum.

They found transgenes from cotton that had been modified to resist insects, herbicides or antibiotics in just under a quarter of the 270 wild cotton seeds assessed for that purpose. One of the contaminated seeds came from a wild plant located 755 kilometres away from the nearest GM cotton plantation. Others were beyond first-generation hybrids because they carried multiple and different transgenes.

According to the researchers, the GM seeds could have been dispersed by long distance lorry drivers transporting seeds for animal feed or oil extraction; by mild or strong winds; by fresh or salt water; or by birds and animals that had eaten them.

Norman Ellstrand, professor of genetics at the University of California, Riverside, United States, said this is the first study that finds transgenes in unmanaged cotton populations. He added that this is third system, after Brassica and bentgrass, in which transgenes have established in the wild

"It also highlights how seed dispersal has been an under-appreciated avenue of transgene movement," he said.

The flow of genes between cultivated GM or non-GM cotton plants and their wild relatives reduces the genetic diversity of cotton. This can have consequences for the environment, food safety and health, as well as legal and commercial implications.

"It is urgent to stop the flow of genes between cultivated and wild plants," Ana Wegier, lead author of the study and a researcher at the National Autonomous University of Mexico's ecology institute, told SciDev.Net.

"Post-harvest seeds must be destroyed and Mexico must have active monitoring, control and mitigation programmes," she said.

But Jonathan Wendel, an expert in the evolution of cotton and head of the Department of Ecology, Evolution, Biology and Organismal Biology at Iowa State University, United States, is cautious about the results of the study.

"The plants they identified may, for various reasons, be not truly wild but derived from cultivated plants. If this is the case, the long distance gene flow between transgene and wild populations reported may reflect human, not natural activity," Wendel told SciDev.Net.

More than 95 per cent of cultivated cotton worldwide was domesticated from G. hirsutum, which originated and diversified in Mexico. The first permits for planting GM cotton in Mexico were granted in 1996.

The study was published in the October edition of Molecular Ecology. Link to abstract.

(By María Elena Hurtado, SciDev.Net, 13/10/2011)