Toxic leak

时间:2019-03-07 03:01:06166网络整理admin

By Andy Coghlan INSECT-KILLING toxins from genetically modified maize plants leak into the soil and persist for weeks, biologists in the US have found. Neither finding was expected, say the researchers, raising questions about the impact of the toxins on soil ecology. Guenther Stotzky and Deepak Saxena of New York University grew a commercial maize variety that is genetically modified to make the Bt toxin, a protein normally made by the soil bacterium Bacillus thuringiensis. The toxin protects the plants against moth larvae that burrow into maize stems. Stotzky and Saxena, working with Saul Flores of the Venezuelan Scientific Research Institute in Caracas, grew the maize in the lab and collected soil extracts from around the roots of the plants. They found Bt toxin in the extracts, which could still kill larvae in standard tests of its activity after 25 days. The toxin could have widespread effects on soil ecology, say Stotzky and Saxena, as Bt maize plants now cover 6 million hectares of farmland in the US. They speculate that its effects might be beneficial, in killing pests that would otherwise damage the roots of crops. But the toxin could also harm benign soil organisms, or select for pests resistant to it. “If the target organisms become resistant, the technology of using the toxin goes down the tubes,” says Stotzky. Environmental groups have seized on the findings. “I think it’s time to revisit the environmental risk assessment for GM maize,” says Sue Mayer of GeneWatch, an environmental lobby group in Buxton,