Further warnings about the risks of GM Crops

14 years ago

Modified Crops Reveal Hidden Cost Of Resistance

(Oct. 29, 2009) Â Genetically modified squash plants that are resistant to a debilitating viral disease become more vulnerable to a fatal bacterial infection, according to biologists.

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"There is concern in the ecological community that, when the transgenes that confer resistance to these viral diseases escape into wild populations, they will (change) those plants," said Stephenson, whose team's findings appear on October 26 in the Proceedings of the National Academy of Sciences. "That could impact the biodiversity of plant communities where wild squash are native."

Stephenson and his colleagues James A. Winsor, professor of biology; Matthew J. Ferrari, research associate; and Miruna A. Sasu, doctoral student, all at Penn State; and Daolin Du, visiting professor, Jiangsu University, China, crossed the genetically modified squash into wild squash native to the southwestern United States and examined the resulting flower and fruit production.

Unlike a lab experiment, the researchers tried to mimic a real world setting during their three-year study.

The researchers then looked at the effects of the virus-resistant transgenes on prevalence of the three viral diseases, herbivory by cucumber beetles, as well as the occurrence of bacterial wilt disease that is spread by the cucumber beetles.

"When the cucumber beetles start to feed on infected plants they pick up the bacteria through their digestive system," explained Sasu. "This feeding creates open wounds on the leaves and when the bugs' feces falls on these open wounds, the bacteria find their way into the plumbing of the plant."

The researchers discovered that as the viral infection swept the fields containing both genetically modified and wild crops, the damage from cucumber beetles is greater on the genetically modified plants. The modified plants are therefore more susceptible to the fatal bacterial wilt disease.

"Plants that do not have the virus-resistant transgene get the viral disease," explained Stephenson, whose team's work is funded by the National Science Foundation. "However, since cucumber beetles prefer to feed on healthy plants rather than viral infected plants, the beetles become increasingly concentrated on the healthy -- mostly transgenic -- plants."

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