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Unintended Effects of Genetic Manipulation
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Herbicide-resistant soybean plants were shorter, with less chlorophyll, lower weight, and increased susceptibility to stem-splitting at high temperatures.

Manipulated Organism: Soybean (Glycine max).

Inserted Transgenes and Intended Effect: CP4 EPSPS gene derived from the common soil bacterium Agrobacterium, sp. Strain CP4. The gene was fused to the cauliflower mosaic virus (CaMV-35S) promoter so that the target gene would be expressed in all parts of the plant. The transgenic soybeans are resistant to the herbicide glyphosate. Glyphosate-resistant soybeans have been grown on millions of acres of farmland since 1996.

Goal of This Study: Gertz et al. responded to complaints of farmers in Georgia in the late 1990s concerning poor performance of the transgenic soybeans under conditions of heat and drought stress. They carried out a comparative study of transgenic and conventional soybeans.

Unintended Effects: In comparison to conventional soybeans the transgenic glyphosate-resistant soybeans
  • were shorter;
  • had lower chlorophyll content in the leaves;
  • had a lower fresh weight; and
  • suffered stem splitting at higher temperatures.

Additional Comments: Gertz et al. conclude: "These data indicate that the advantage of glyphosate resistance may come at the expense of physiological heat stress tolerance in the varieties examined. . . . The current system that imparts glyphosate resistance in glyphosate-resistant soybeans makes them inherently sensitive to stress." The report by Gertz et al. appeared in the proceedings of a conference, not in a peer-reviewed journal. For a response to Gertz et al. by Monsanto Company, which sells glyphosate-resistant soybeans under the name Roundup Ready®, see: http://www.monsanto.co.uk/news/ukshowlib.phtml?uid=2507.

Source: Gertz, J.M., W.K. Vencill, and N.S. Hill (1999). "Tolerance of Transgenic Soybean (Glycine max) to Heat Stress," The 1999 Brighton Conference: Weeds. Farnham, Surrey, UK: The Council, pp. 835-40.

Author Affiliations: Department of Crop and Soil Sciences, University of Georgia, USA.

Funding: Not mentioned.

Product Status: Monsanto's Roundup Ready® soybeans have been on the market since 1996.

Copyright 2008 The Nature Institute.

This document: http://natureinstitute.org/nontarget/reports/soybean_001.php

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