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Glyphosate-resistant soybeans had lower yields.

Manipulated Organism: Soybean (Glycine max).

Inserted Transgenes: CP4 EPSPS gene cloned from Agrobacterium, which produces an herbicide-resistant version of the enzyme targeted by the herbicide glyphosate (Roundup).

Goal of This Study: According to the authors, "potential yield suppression associated with GR [glyphosate-resistant] cultivars is a concern of producers and seed companies" (p. 408). This possibility was investigated by comparing the yields of GR soybean cultivars and their near-isogenic sister lines over two years at several sites in Nebraska.

Results of This Study:
  • GR cultivars had on average 5% lower yield than their near-isogenic sister lines, as well as 4% smaller seed weight.
  • In a previous study, no significant yield differences were observed when GR cultivars were sprayed with glyphosate or weeded by hand. In light of these results, the authors conclude that "yield suppression appears associated with the GR gene or its insertion process rather than glyphosate itself" (p. 411).

Source: Elmore, R. W., F. W. Roeth, L. A. Nelson, C. A. Shapiro et al. (2001). "Glyphosate-resistant Soybean Cultivar Yields Compared with Sister Lines," Agronomy Journal vol. 93, pp. 408-12.

Author Affiliations: University of Nebraska.

Funding: Nebraska Soybean Board.

Product Status: GR soybeans have been grown commercially in the US since 1996 and currently constitute over 90% of the US soybean crop.

Copyright 2009 The Nature Institute.

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