Novel food information: Imidazolinone tolerant (IT) corn

On this page

• Background
• Introduction
• Development and production of the modified plant
• Product information
• Dietary exposure
• Nutrition
• Toxicology
• Conclusion

Background

Health Canada has notified Pioneer Hi-Bred International, Inc. that it has no objection to the food use of grain from the genetically modified IT Corn line, which is tolerant to imidazolinone herbicides. The Department conducted a comprehensive assessment of IT Corn according to it's 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 Pioneer Hi-Bred International, Inc. notification to Health Canada and contains no confidential business information.

Introduction

Pioneer Hi-Bred International, Inc. (Pioneer) has licensed an imidazolinone tolerant corn line from American Cyanamid that was used to develop new corn hybrids with herbicide tolerance. The mutation is known as XI-12 and the resulting hybrids as IT hybrids. The IT hybrids are very similar to imidazolinone resistant (IR) hybrids in their mechanism of herbicide resistance. IR hybrids were reviewed by Health Canada in 1995 as a novel food and determined to be safe for food consumption in Canada.

Development and production of the modified plant

Corn is grown widely throughout North America as a food and feed crop. Corn is a commodity crop largely used to feed domestic animals, either as grain or silage. The remainder of the crop is exported or processed by wet or dry milling to yield products such as high fructose corn syrup and starch, oil, grits, and flour. The imidazolinone tolerant corn (IT corn) was developed through mutation breeding. No foreign DNA was introduced to achieve the herbicide tolerance trait.

The method used for obtaining imidazolinone-tolerant corn plants was in vitro selection. The mutation conferring imidazolinone tolerance is referred to as XI-12. The XI-12 mutation affects the acetohydroxyacid synthase (AHAS) enzyme of maize at a specific location. The AHAS enzyme catalyses the first step in the biosynthesis of the branched chain amino acids isoleucine, leucine, and valine in corn. The mutation in the AHAS enzyme results in an alteration to the binding site for the imidazolinone class of herbicides, therefore increasing the plant's tolerance to those herbicides.

Product information

A mutation to the AHAS enzyme in corn could affect the biosynthesis of the essential amino acids isoleucine, leucine, and valine. The amino acid composition of an XI-12 hybrid and Pioneer^® Brand hybrid 3394 was analysed in grain from field grown plants. The results of the amino acid analyses demonstrate that corn hybrids containing the XI-12 mutation do not show altered levels of valine, leucine, and isoleucine. It can be concluded that the single amino acid substitution in the XI-12 mutation results in maize hybrids, which are unchanged in their AHAS enzyme activity.

Dietary exposure

It is not anticipated that the dietary exposure to maize-based products will increase as a result of the sale of IT hybrids. Farmers grow many different maize hybrids based on such factors as geographical location, soil type, climate, prevalent diseases and pests and price. Moreover, the growing environment can markedly affect grain composition. This results in a wide variation in the composition of commercial maize grain. Extensive mixing during storage, transportation and processing helps ensure consistency in composition of the commodity grain supply. Minor variations in composition of grain from one or two hybrids will be of no nutritional consequence since it will be mixed with grain from many other hybrids.

Nutrition

The data presented on the amino acid composition of IT corn demonstrates that the XI-12 mutation does not alter AHAS enzyme activity based on the levels of valine, leucine, and isoleucine. It can be concluded that hybrids derived from XI-12 are also unchanged in their nutritional and food safety characteristics.

Toxicology

No toxicity concerns are associated with the expression of the imidazolinone tolerance trait in IT corn hybrids.

No new protein, or significantly altered protein, is produced through this genetic modification. No allergenicity concerns are associated with the expression of the imidazolinone tolerance trait in IT corn hybrids.

Conclusion

Single amino acid substitutions can affect the binding of AHAS inhibitors, such as imidazolinone herbicides, but there appears to be no significant change in enzyme function, as reflected in studies comparing the XA-17 and XI-12 mutations. It can be concluded that the single amino acid substitution in the XI-12 mutation will result in IT corn hybrids which are unchanged in their nutritional and food safety characteristics when compared to IR hybrids and normal maize hybrids currently on the market in Canada.

Health Canada's opinion deals only with the food use of IT corn. Issues related to growing IT corn in Canada and its use as animal feed are addressed separately through existing regulatory processes in the Canadian Food Inspection Agency.

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
Food Directorate
Health Products and Food Branch
Health Canada, PL2204A1
251 Frederick Banting Driveway
Ottawa, Ontario K1A 0K9
bmh-bdm@hc-sc.gc.ca