Novel food information: Glufosinate resistant maize (corn), DLL25
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- Development of the modified plant
- Product information
- Dietary exposure
Health Canada has notified DEKALB Genetics Corporation that it has no objection to the food use of the transgenic maize line DLL25, which is resistant to glufosinate herbicides. The Department conducted a comprehensive assessment of DLL25 according to its Guidelines for the Safety Assessment of Novel Foods (September 1994). These guidelines are based upon internationally accepted principles for establishing the safety of foods derived from genetically modified organisms.
The following provides a summary regarding the DEKALB Genetics Corporation notification to Health Canada and contains no confidential business information.
Maize line DLL25 was developed through genetic modification to be resistant to glufosinate (also known as phosphinothricin, the active ingredient in the herbicides Basta®, Rely®, Ignite®and Liberty®). The modification permits farmers to use the broad-spectrum glufosinate herbicides for weed control in the cultivation of corn.
Development of the modified plant
The DLL25 maize line was created by microprojectile bombardment of cultured maize cells (also known as corn or Zea mays L.) with tungsten particles coated with DNA. This DNA introduced the bar gene, which was originally isolated from a common soil bacterium, Streptomyces hygroscopicus, and encodes the protein phosphinothricin acetyltransferase (PAT).
Also included on the introduced DNA is the -lactamase gene which encodes resistance to the antibiotic ampicillin. This gene was included as a selectable marker for the development of the introduced DNA in bacteria but is not functional in plants.
Expression of the bar gene in DLL25 plants results in the production of the PAT protein. This occurs in most, but not all, tissues of the corn plant. PAT levels are highest in leaves, with lower levels in roots, prop roots, stalk, tassel, cob, husk, and kernels. No PAT protein has been detected in silk or pollen. Stability of expression was demonstrated to be consistent across several hybrids derived from DLL25, across several generations. The only newly expressed material in DLL25 is the PAT protein. The PAT protein is an enzyme which is highly specific for glufosinate and is not expected to have any effect on metabolic pathways in the plant other than detoxification of glufosinate herbicides. Agronomic performance and nutritional composition data (see section 5) demonstrated that DLL25 hybrids are comparable to their non-transgenic counterparts.
Grain from DLL25 is primarily intended for animal feeding. However, such field corn may be dry- or wetmilled into various processed corn products for human food use. The human food uses of grain from DLL25 is not expected to be different from the uses of non-transgenic field corn varieties. As such, the dietary exposure of Canadians to grain from DLL25 will not be different from that for other commercially available field corn varieties.
Forage and grain from DLL25 maize hybrids were analyzed for nutritional composition and compared to the nutritional composition of non-transgenic versions of the same maize hybrids. Proximate and amino acid analyses were performed. Small differences between DLL25 plants and their non-transgenic counterparts were occasionally observed. However, the nutrient composition of DLL25 maize falls within the range of variability for the relevant nutrients reported for maize. The use of corn products derived from DLL25 would therefore have no significant impact on the nutritional quality of the Canadian food supply.
a. Potential toxicity
The PAT protein was compared to databases of known protein toxins and shows no homology to known protein toxins. PAT protein is rapidly degraded under conditions that simulate mammalian digestion. An acute mouse toxicity study was performed with no toxicity observed. Based on the results of the study, the acute oral LD50 was estimated to be greater than 2500 mg of PAT/kg body weight.
b. Potential allergenicity
The PAT proteins is extremely unlikely to be an allergen. The introduced protein was compared to known allergens and demonstrated to not share homology to known allergens. In addition, the potential for allergicity was assessed based upon the characteristics of known food allergens (stability to digestion, stability to processing). The PAT protein does not possess characteristics typical of known protein allergens.
Health Canad'as review of the information presented in support of the food use of glufosinate resistant maize DLL25 concluded that this maize does not raise concerns related to safety. Health Canada is of the opinion that DLL25 is as safe and nutritious as current commercial maize varieties.
Health Canada's opinion deals only with the food use of this glufosinate resistant maize. Issues related to growing glufosinate resistant maize in Canada and its use as animal feed have been addressed separately through existing regulatory processes in Agriculture & Agri-Food Canada.
This Novel Food Information document has been prepared to summarize the opinion regarding the subject product provided by the Food Directorate, Health Products and Food Branch, Health Canada. This opinion is based upon the comprehensive review of information submitted by the petitioner according to the Guidelines for the Safety Assessment of Novel Foods (September 1994).
For further information, please contact:
Novel Foods Section
Health Products and Food Branch
Health Canada, PL2204A1
251 Frederick Banting Driveway
Ottawa, Ontario K1A 0K9
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