Novel food information: Imidazolinone tolerant ClearfieldTM wheat AP205CL

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Health Canada has notified BASF Canada Inc. that it has no objection to the food use of grain from the Triticum aestivum line AP205CL 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 (September 1994). These Guidelines are based upon internationally accepted principles for establishing the safety of foods with novel traits.

The following provides a summary of the BASF Canada Inc. notification to Health Canada and the results of the safety assessment. This summary contains no confidential business information.


BASF Canada developed wheat line AP205CL, which is tolerant to imidazolinone herbicides, through a combination of mutagenesis and conventional breeding. No novel DNA has been introduced into the wheat line to achieve the herbicide tolerant phenotype. 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 AP206CL and SWP965001.

Development and production of the modified plant

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.

The petitioner has provided information describing the methods used to develop wheat line AP205CL and data that characterizes the genetic change which confers tolerance to imidazolinone herbicides. Seed from the hard red spring wheat variety gunner was mutagenized using ethyl methanesulfonate (EMS) and diethyl sulfate (DES). These mutagens are commonly used in plant breeding and generate nucleic acid substitution mutations.

The mutation responsible for imidazolinone tolerance is due to a point mutation of a single nucleotide in one of three AHAS genes found in AP205CL (Triticum aestivum has three genomes). The petitioner has identified the mutation in the AHAS gene which confers herbicide tolerance by sequencing. The altered gene contains a mutation which results in a codon change from ACG to AAC, producing an amino acid change from serine to asparagine. As with the previously approved imidazolinone tolerant wheats, rice, corn and canola, the single 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. During development, AP205CL was backcrossed with its parent gunner to recover the genotype of the parent while keeping the imidazolinone tolerant trait.

Product information

A mutation in the AHAS enzyme in wheat could potentially affect the biosynthesis of the essential amino acids isoleucine, leucine, and valine. The amino acid composition of ClearfieldTM wheat line 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.

Dietary exposure

Imidazolinone tolerant ClearfieldTM wheat line AP205CL is expected to be used in similar applications to 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.


The wheat grain samples were analyzed for proximates (moisture, crude fat, protein, crude fibre), amino acids, minerals (iron, magnesium, phosphorous, and zinc), vitamins (niacin, pantothenic acid, thiamin, vitamin B6, and vitamin E) fatty acids and antinutrients (phytic acid and trypsin inhibitor). There were significant differences found between the AP205CL and gunner varieties in the levels of two fatty acids, oleic and palmitic acids, however, these differences are not biologically significant in wheat grain since the fat content of the grain is less than 2% and these fatty acids make up only a portion of the fat. If the wheat germ oil were extracted and used as an ingredient, the differences would still not be considered biologically significant since the levels in the ClearfieldTM wheat fall within the range of variation for these fatty acids as shown by the control varieties in the study and data reported in the scientific literature.


The weight of evidence suggests that the mutant AHAS enzyme from AP205CL wheat is unlikely to be a toxin or allergen under normal conditions of consumption. 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 by trypsin as the native protein. Consequently, systemic exposure to the intact AHAS was considered negligible. Further, the modified AHAS protein is not homologous to known allergens and did not differ from native AHAS in its similarity to known food allergens. In addition, the AP205CL wheat does not express any new major proteins or altered amounts of other proteins, including endogenous wheat allergens, as demonstrated by comparing protein extracts from AP205CL and its unmodified parent by reverse phase high performance liquid chromatography.


Health Canada's review of the information presented in support of the food use of imidazolinone tolerant wheat line AP205CL concluded that the food use of grain from this wheat line does not raise concerns related to safety or nutrition. ClearfieldTM wheat variety AP205CL 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 deals only with the food use of imidazolinone tolerant wheat variety AP205CL. Issues related to its use as animal feed have been 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

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