Herbicide-resistant soybean plants were shorter, with less chlorophyll,
lower weight, and increased susceptibility to stem-splitting at high
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.
In comparison to conventional soybeans the transgenic glyphosate-resistant
had lower chlorophyll content in the leaves;
had a lower fresh weight; and
suffered stem splitting at higher temperatures.
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:
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.
Department of Crop and Soil Sciences, University of Georgia, USA.
Monsanto's Roundup Ready® soybeans have been on the market since 1996.
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