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Leakage of transgenic proteins into soil

Many plants leak chemical compounds into the soil through their roots. There are concerns that transgenic plants may leak different compounds than conventional plants do, as an unintended consequence of their changed DNA. Speculation that this may be happening leads to concern about whether the communities of micro-organisms living near transgenic plants may be affected. The interaction between plants and soil micro-organisms is very complex, with the micro-organisms that live around plant roots also leaking chemical compounds into the soil. Much more research must be done before we understand the relationships that occur between micro-organisms and conventional crops. Attempts to discover whether transgenic plants are changing the soil environment, and whether they are changing it in good ways or bad ways, are hindered by our lack of basic scientific knowledge.

A few studies have attempted to describe conditions in soils where transgenic crops are grown. A Canadian study (Dunfield and Germida, 2001), tested the soils around four transgenic and four conventional canola varieties. Some differences were associated with whether the crop being grown was transgenic or conventional. Other soil characteristics were similar regardless of the crop type, and some differences were not associated with the crop type. An analysis of fatty acids that are associated with certain kinds of soil micro-organisms indicated that transgenic plant roots might harbor higher levels of certain micro-organisms, but further research is essential to determine whether this is true.

Image: Rural Life Center, Kenyon College.

Bt corn roots leak Bt toxin into the soil, and this toxin is known to bind to certain soil components, where it has the potential to remain for more than 200 days, protected from degradation and retaining its ability to kill insect larvae (Saxena et al., 1999). This characteristic would be considered an advantage if the target of the toxin is a soil-living insect. It is not known whether leakage from roots will lead to a long-term buildup of Bt toxin in the soil of corn fields or how this might affect non-target micro-organisms or insects living in the soil.

One report published in the Canadian newspaper Le Devoir (Gravel, 2001, POLLUTE THE SAINT LA) claimed that sediments taken from Quebec's Saint Lawrence river near a field of Bt corn contained five times more Bt toxin than samples taken from drainage water and sediments around the field. The results were mentioned at an international symposium in a presentation by Professor Jean-Francois Narbonne of the University of Bourdeaux. Another scientist associated with the research project is reported to have said that the Bt levels in the river sediment were "trace amounts" rather than high levels ( Further research is necessary to clarify the results of the research. It is unknown whether Bt toxin in river sediments will have any effect on river organisms.

Page last updated : March 11, 2004

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