ARCHIVED - Imidazolinone Tolerant Clearfeild Wheat AP602CL

Novel Food Information - Biotechnology

Health Canada has notified BASF Canada that it has no objection to the food use of Clearfield wheat (Triticum aestivum) line AP602CL derived through mutation breeding, which is tolerant to imidazolinone herbicides. The Department conducted a comprehensive assessment of this wheat according to its Guidelines for the Safety Assessment of Novel Foods. These Guidelines are based upon internationally accepted principles for establishing the safety of foods with novel traits.


The following provides a summary regarding the BASF notification to Health Canada and contains no confidential business information.

1. Introduction

BASF Canada has developed a wheat variety that is tolerant to imidazolinone herbicides through a combination of mutagenesis and conventional breeding. The mutation responsible for imidazolinone tolerance is due to a point mutation of a single nucleotide in the acetohydroxyacid synthase (AHAS) gene, similar to that previously described for imidazolinone tolerant corn, canola, rice and wheat lines evaluated by Health Canada.

2. Development of the Modified Plant

Seeds of the hard red spring wheat variety Gunner were subjected to chemical-induced mutagenesis using ethylmethane sulfonate (EMS) and diethyl sulfate (DES). Mutants were selected based on imidazolinone tolerance and further bred using conventional breeding techniques. Imidazolinone tolerant variety AP602CL was chosen for commercialization based on agronomic and grain quality characteristics.

The mutation which confers herbicide tolerance in AP602CL was identified by enzyme activity analysis, Mendelian genetics and DNA sequencing. A codon change caused by a single nucleotide substitution in the AHAS gene results in a single amino acid change of serine to asparagine in the AHAS enzyme. This amino acid change alters the binding site for the herbicide on the AHAS enzyme while having no effect on the normal functioning of the enzyme. Previously approved imidazolinone tolerant rice, corn, canola, and wheat lines were the result of a similar single nucleotide substitution in the AHAS gene.

3. Product Information

A mutation in the AHAS enzyme in wheat could affect the biosynthesis of the essential amino acids isoleucine, leucine, and valine. The amino acid composition of Clearfield wheat variety AP602CL was compared to commercial cultivars, however, and it was confirmed that the AHAS activity of the imidazolinone-tolerant wheat was not affected by the mutation.

4. Dietary Exposure

Wheat is grown widely throughout North America as a food and feed crop. The principal use of wheat grain is the production of flour which, depending on the specific type of wheat, is used in many baked goods and other food products. Imidazolinone tolerant Clearfield wheat line AP602CL is expected to be used in similar applications as other wheat varieties by the food industry. Since there would not be expected to be any change to the gluten content of this variety of wheat, there is no new or additional concern for individuals with celiac disease.

5. Nutrition

The nutrient data pertaining to Clearfield wheat variety AP602CL comprised the analyses of grain samples for proximates (moisture, crude fat, protein, crude fibre), amino acids, fatty acids, minerals (phosphorus, zinc, magnesium, iron), vitamins (thiamin, niacin, pantothenic acid, vitamin B6, and vitamin E), phytic acid, and trypsin inhibitor. The nutrient data demonstrates that the nutritional composition of grain from the AP602CL herbicide tolerant wheat variety is not significantly different from grain derived from the parent variety Gunner.

6. Toxicology

There are no toxicity or allergenicity concerns associated with the expression of the imidazolinone tolerance trait in wheat variety AP602CL. This conclusion is based on the observations that the protein is present in very low amounts in the edible part of the wheat, its activity is heat-labile and would be destroyed during normal food preparation processes, and the protein is as sensitive to degradation in the human gastrointestinal tract. Further, the mutant AHAS protein is not homologous to known allergens and mutagenized AHAS did not differ from native AHAS in its similarity to known food allergens. Lastly, the AP602CL wheat does not express any new major proteins or altered amounts of other proteins, including endogenous wheat allergens.


Health Canada's review of the information presented in support of the food use of imidazolinone tolerant wheat variety AP602CL, concluded that this line does not present human food safety concerns. Clearfield wheat variety AP602CL is unchanged in its nutritional and food safety characteristics when compared to other wheat varieties currently available on the Canadian marketplace.

Health Canada's opinion pertains only to the food use of Clearfield wheat variety AP602CL. Issues related to 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.

(Également disponible en français)

For further information, please contact:

Office of Food Biotechnology
Food Directorate
Health Products and Food Branch
Health Canada
Tunney's Pasture
Ottawa, Ontario K1A 0L2
Telephone: (613) 941-5535
Facsimile: (613) 952-6400
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