Bt From Transgenic Plants Found In Soil Guenther Stotzky and researchers at New York University have shown that Bt maize, the seed variety which is resistant to corn borer pests, releases the Bacillus thuringiensis toxin through its roots into the soil. However, scientists are undecided as to whether this represents a potential hazard, or benefit, of GM maize. Stotzky and his colleagues report in Nature that the toxin remains in the soil as it is not easily broken down, and remains insecticidal. This could help the control of pests or increase the speed of development of insect-resistant pests. About one-fifth of the maize (Zea mays) planted in the USA last year was genetically modified so that it could produce an insecticide to protect itself against the ravages of pests such as caterpillars. This insecticide has been dubbed Bt toxin, after the bacterium that is its natural producer. Whether what is good for the maize might be bad for the network of insect communities in the vicinity, and how engineered Bt toxin compares with traditional insecticide treatments, are questions currently fuelling scientific and political debate. In Stotzky et al.'s Brief Communication, they describe how they identified the fully active toxin in soil surrounding the roots of Bt maize, but not those of unmodified maize, grown under greenhouse conditions. The toxin in the soil remained active during 25 days of plant growth, probably because, being bound to soil particles, it is protected against biodegradation. Although we cannot draw any conclusions about how the results from this laboratory study might affect all the different creatures that live under a real field of Bt maize, it is possible that these underground exudates may eventually turn out to be helpful in controlling root pests. They suggest that non-target insects and other organisms could be affected. Monsanto scientists say that soil degradation is only one of the components in assessing the potential impact of Bt proteins expressed in transgenic plants on soil ecology/environment. They report that insecticidal specificity is defined for each protein as well as assessing that the Bt protein has no adverse effects on non-target, beneficial insects (including soil invertebrates). All Bt proteins in Monsanto's transgenic plants are highly selective and no adverse effects have been observed, according to the company. It says soil degradation has been directly assessed for each Bt protein in the transgenic plant matrix. The Bt protein in each transgenic plant to date has degraded comparably or more rapidly than the microbial Bt products. In contrast, field information from the transgenic plants have shown significant increases in beneficial insects, as expected, thereby establishing clear environmental and ecological benefits compared to current insect control alternatives, it says. The paper, "Insecticidal toxin in root exudates from Bt corn" by Deepak Saxena, Saul Flores and G. Stotzky appears in Nature (1999) 402, 480. December 1999 -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] Archive: http://www.mail-archive.com/[email protected]/
