Science in Society Archive

Syngenta's GM Maize Scandals

A trail of unstable GM maize varieties, dead cows, cross-contamination and misinformation. Prof. Joe Cummins and Dr. Mae-Wan Ho demand a full disclosure of all available data for damage limitation

Farmers who bought Syngenta’s genetically modified (GM) maize Bt11 may, in fact have got more than they bargained for, because many received another GM variety Bt10 that may be worse. The news broke in the science journal Nature. Several hundred tonnes of the unapproved GM maize variety Bt10 had been "inadvertently" distributed under the Bt11 label between the years 2001 and 2004. Syngenta claimed that Bt11 and Bt10 are physically identical [1], but this is impossible to achieve in the current state of the GM technology, and is at odds with its own reports to USDA/APHIS in 1994.

Eleven years ago the Northrup-King company (later taken over by Syngenta) reported that Bt10 produced several times less toxin than Bt11 even though the two lines were modified with similar sets of transgenes; but the transgenes had inserted at different sites in the maize genome.

Bt11 has been approved for consumption in Argentina, Australia, Canada, China, European Union, Japan, Korea, Philippines, Russia, South Africa, Switzerland, Taiwan, United Kingdom, United States and Uruguay [2]. Northrop-King Company consulted the US Food and Drug Agency (FDA), and provided minimal evidence that the maize strain was substantially equivalent to unmodified maize [3, 4]. It applied for non-regulated status in the US in 1995, which USDA/APHIS granted a year later [5].

Substituting the unapproved GM maize Bt10 for Bt11 is a very serious breach of safety. But Bt11 maize is already bad enough, and should never have been approved ("Approval of Bt11 maize endangers humans and livestock", SiS 23). The European Commission gave it approval in May 2004 when expert committees repeatedly failed to reach an agreement. French and Belgian government scientists had reported "rearrangements, truncations and unexpected insertions" in Bt11. The main insert appeared to have landed in what turns out to be a suspected "megatransposon" involved in exchanging segments between chromosomes, making the variety potentially very unstable. Bt11 was also contaminated with another Syngenta GM maize, Bt176, also found to be unstable and misidentified ("Unstable transgenic lines illegal SiS 21), and was implicated in the death of at least a dozen dairy cows in Hesse Germany ("Cows ate GM maize and died", SiS 21). Watch this space.

According to the petition from Northup-King [6], Bt11 (and also Bt10) was constructed using the Cry1Ab toxin gene from Bacillus thuringiensis var kurstaki that had been altered extensively and the protein shortened to enhance expression in maize, and controlled by a cauliflower mosaic virus 35S promoter enhanced by a maize alcohol dehydrogenase intron, and the nos transcription terminator from Agrobacterium. A second transgene coding for phosphoinothricin acetyl transferase (PAT) from Streptomyces, also altered extensively and controlled by the same promoter and terminator, confers resistance to the herbicide glufosinate; although the GM maize was not marketed as herbicide resistance. The two structural genes were inserted into the long arm of maize chromosome 8, it was claimed.

An appendix [7] to the Northrup King petition compared the production of the events Bt11 and Bt10. The Bt10 event was not characterized as to the chromosomal site of integration nor was there extensive analysis of the gene inserts and their protein products. The study showed that Bt11 produced about seven times more toxin protein than Bt10, indicating a clear difference between the two events. Farmers unknowingly planting Bt10 in place of Bt11 would be prone to experience insect resistance in the low toxin maize.

An advice on Bt11 from UK’s ACRE (Advisory Committee on Releases to the Environment) [8], made reference to data provided by Syngenta to support its claim that the ampicillin resistance marker gene was absent from Bt11, in which Bt10 was used as a positive control. This implies that the antibiotic resistance marker gene is indeed present in Bt10. Syngenta has now admitted to this [9], but a spokesperson from the company downplayed the significance of the antibiotic resistance marker gene. Ampicillin is a widely used clinical antibiotic, and the European Food Safety Authority, the Codex Alimentarius, and many medical and scientific experts have recommended against using antibiotic resistance genes in GM foods, hence Bt10 is unlikely to have received regulatory approval in Europe.

There are also as yet unconfirmed reports that the Bt10 inserts have a promoter different from Bt11 and that the enhancer has been altered.

The Australia-New Zealand Food Authority reported that the Bt11 PAT gene is driven by the 35S figwort mosaic virus [10] instead of the 35SCaMV promoter reported to USDA/APHIS and the European regulatory authorities. The Canadian Food Inspection Agency reported more than one Cry1Ab toxin protein produced in Bt11, these included proteins of 69kDa, 65kDa and two minor ones of 40kDa and 15kDa [11]; suggesting that the toxin is processed or degraded in Bt11 maize. The toxins produced in event Bt10 have not been reported to public and this information should be made available immediately.

There was a long delay between the discovery of large plantings of Bt10 and the report to the public. Syngenta, the FDA [12] and UK DEFRA (Department of the Environment, Food and Rural Affairs) [13] have all initially claimed that Bt10 and Bt11 are identical. This claim was made in the face of clear evidence that the two events were different, according to information available to UK’s ACRE at least since 2003 [14].

There must now be a full disclosure of all available data to limit the damages being done.

Article first published 30/03/05


  1. Macilwain C. US launches probe into sales of unapproved transgenic corn, Nature 2005, 434, 424.
  2. Agbios Bt11 approvals
  3. US Food and Drug Administration Biotechnology Consultation Agency Response Letter BNF No.000017 1996
  4. US Food and Drug Administration Biotechnology Consultation Note on the File BNF No.000017 1996
  5. Payne J. USDA/APHIS Petition 95-195-01 for Determination of Nonregulated Status for Bt11 Corn 1996.
  6. Pilacinski W and Williams D. Petition for Determination of Nonreguloated Status for: Insect protection corn expressing the Cry1Ab gene from Bacillus thuringiensis var. kurstaki 1995.
  7. Hanten J and Meeusen R. Petition for Determination of Nonreguloated Status for: Insect protection corn expressing the Cry1Ab gene from Bacillus thuringiensis var. kurstaki Appendix G Determination of levels of plant produced Bacillus thuringiensis kuastaki HD-1 proteins in transgenic maize. 1994.
  8. Advisory Committee on Releases to the Environment. Advice on a notification for marketing of insect resistant and herbicide tolerant GM maize.
  9. "Stray seeds had antibiotic-resistance genes" Colin Macilwain, Nature online, 29 March 2005.
  10. Australia-NewZealand Food Authority Draft Risk Analysis Report Application A386 Food derived from insect protected herbicide tolerant Bt11 corn 2000.
  11. Canadian Food Inspection Agency Decision Document DD96-12: determination of environment safety of Northrup King Seeds European corn borer resistant corn 1996.
  12. Press Release: Following Syngenta-initiated investigation of unintended corn release, EPA and USDA conclude existing food safety clearance applies, no human health or environmental concerns, Washington, DC (USA), 21 March 2005, Syngenta web site.
  13. DEFRA Press Release, 23 March 2005 (see below)
  14. "DEFRA accused of key role in GM contamination cover-up", Press Notice from GM Free Cymru 30 March 2005

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