Novel food information: Clearfield™ bread wheat variety BW
On this page:
- Development of the modified plant
- Characterization of the modified plant
- Product information
- Dietary exposure
Health Canada has notified BASF Canada Inc. that it has no objection to the food use of Bread wheat variety (BW7) with an Als1b imidazolinone tolerance trait. The Department conducted a comprehensive assessment of these varieties 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 notification from BASF Canada Inc. and the evaluation by Heath Canada and contains no confidential business information.
The imidazolinone tolerance trait in bread wheat variety BW7 was introduced through chemical mutagenesis of seed and traditional breeding. Exposure to a chemical mutagen causes a genetic change that results in an alteration to the acetohydroxyacid synthase (AHAS) protein produced by the Als1 gene. These changes cause this variety to grow in the presence of imidazolinone herbicides. Health Canada has previously indicated no objection to the sale of imidazolinone tolerant corn (XI-12), canola (NS738, NS1471, NS1473), rice (CL121, CL141, CFX51, PWC16, CL IMINTA 1 and CL IMINTA 4), lentils (RH44), sunflower (X81359), bread wheat (AP602CL, AP205CL, Teal11A, BW 255-2 and BW238-3) and durum wheat (DW1 and DW12) in the Canadian marketplace.
The assessment conducted by Food Directorate evaluators determined how Clearfield™ bread wheat variety BW7 was developed; how its composition and nutritional quality compares to traditional bread wheats; and the potential for the presence of any toxicants, anti-nutrients, or allergens. BASF has provided data which demonstrates that Clearfield™ bread wheat variety BW7 is as safe and nutritious as the conventional bread wheat varieties sold in Canada.
The Food Program has a legislated responsibility for pre-market assessment of novel foods and novel food ingredients as detailed in the Food and Drug Regulations (Division 28). Food use of bread wheat variety BW7 is considered a novel food under the following part of the definition of novel foods: "c) a food that is derived from a plant, animal or microorganism that has been genetically modified such that
- the plant, animal or microorganism exhibits characteristics that were not previously observed in that plant, animal or microorganism."
Development of the modified plant
Imidazolinone tolerant wheat variety BW7 was developed using seed mutagenesis with sodium azide from the parental winter wheat variety. Treated seeds were grown as the M1 generation to produce M2 generation seeds. The M2 generation and each subsequent generation until M6 were screened using imazamox for herbicide tolerance. This process has been described by the petitioner and is similar to those used in previously approved Clearfield™ products. Currently BW7 has been bred to the M9 generation by self pollination.
The target of the imidazolinone class of herbicides is the enzyme AHAS which is responsible for the first step in the biosynthesis of essential branched chain amino acids. The mutation which results in the tolerance to imidazolinone herbicides in BW7 is a single nucleotide change in the AHAS coding region, resulting in a single amino acid change in the expressed protein. The single amino acid change alters the binding site for the herbicide on the AHAS enzyme expressed by this Als gene while having no effect on the normal functioning of the enzyme.
Characterization of the modified plant
The petitioner has provided data from sequencing studies comparing cloned Als gene sequences from both BW7 and wildtype plants have confirmed this single base substitution in the Als1 coding region. Additionally, the petitioner provided data that confirms that no alterations in the coding regions of Als2 of Als3 has occurred in BW7. This study confirms that herbicide tolerance in this variety is the result of a single base change in the coding region of Als1.
The AHAS enzyme produced by this line has been shown to have similar activity to that produced by the wild type parental line. The mutation in the Als1 gene, A1s1b, has been shown to be stably inherited in BW7 This has been shown through consistent tolerance to imidazolinone herbicides in generations M1 to M6 and through sequencing data generated from the M5 and M8 generations. Additionally, the petitioner has presented data demonstrating that this trait is inherited in the expected Mendelian fashion.
Bread Wheat variety BW7 differs from its traditional counterparts in that it is tolerant to Imidazolinone herbicides. This is due to a mutation in the AHAS enzyme produced by Als. 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™ bread wheat variety BW7 was compared to its parent, confirming that the AHAS activity of the imidazolinone-tolerant wheat was not affected by the mutation.
Bread Wheat variety BW7 is expected to be used in similar applications as traditional bread wheat varieties by the food industry.
Nutrient and anti-nutrient composition was determined for grain samples of the test variety (BW7) and parental control grown in 2002-2003, and 2005 in eight field sites (five locations in Kansas/USA and three locations in Nebraska/USA). In addition, the nutrient and anti-nutrient content of BW7 wheat was compared to other conventional wheat varieties using a database of grain composition of wheat varieties grown in the U.S. and Canada.
The components analysed included: moisture, crude fat, protein, crude fibre, ADF, NDF and TDF, 18 amino acids, 33 fatty acids, 9 minerals (phosphorus, zinc, magnesium, iron, copper, manganese, calcium, sodium, and potassium), 7 vitamins (thiamin/B1, niacin, pantothenic acid, pyridoxine/B6, vitamin E, vitamin B2 and folic acid), and the anti-nutrients phytic acid and trypsin inhibitor.
There were very few statistically significant differences between the control and test variety (fatty acids, phosphorus, zinc, and vitamin B6). For these nutrients, the differences were small, and they were observed only during one period (2002-2003 field trials or 2005 field trials) or in the case of oleic acid, differences were in the opposite direction in 2002-2003 compared to 2005. Consequently, it was concluded that these differences could be considered not nutritionally significant. As well, the levels of nutrients and anti-nutrients in BW7 were comparable to the levels in the other conventional wheat varieties.
The weight of evidence suggests that the mutagenized AHAS expressed in BW7 bread wheat is unlikely to demonstrate toxic or allergenic properties under usual conditions of consumption. This conclusion is based on the observations that the protein is expressed in extremely low amounts in the edible part of the wheat, its activity is heat-labile and would be denatured during normal food preparation processes, and the protein is as sensitive to degradation in a simulated human gastrointestinal tract by trypsin as the native protein. The mutant AHAS protein is not homologous with any known toxins or allergens. Consequently, systemic exposure to the active AHAS protein was considered negligible and it does not share the characteristics of common food allergens.
The mutant AHAS protein is not homologous with any known toxins or allergens. Further, the mutant BW7 bread wheat variety does not express any new major proteins or altered amounts of other proteins, including endogenous wheat allergens. Consequently, systemic exposure to the active AHAS protein was considered negligible and it does not share the characteristics of common food allergens.
Health Canada's review of the information presented in support of the food use of imidazolinone tolerant bread wheat variety BW7 does not raise concerns related to food safety. Health Canada is of the opinion that food derived from bread wheat variety BW7 is as safe and nutritious as food from current commercial bread wheat varieties.
Health Canada's opinion deals only with the food use of imidazolinone tolerant bread wheat variety BW7. 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
Health Products and Food Branch
Health Canada, PL2204A1
251 Frederick Banting Driveway
Ottawa, Ontario K1A 0K9
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