Novel food information: Clearfield™ rice varieties with an Als imidazolinone tolerance trait

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Health Canada has notified BASF Canada Inc. that it has no objection to the food use of rice varieties (CL IMINTA 1 and CL IMINTA 4) with an Als 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 rice varieties CL IMINTA 1 and CL IMINTA 4 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 AHAS protein produced by the Als gene in rice. This change causes the plant 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, and PWC16), lentils (RH44), sunflower (X81359) and wheat (AP602CL, AP205CL, Teal11A, BW 255-2 and BW238-3) in the Canadian marketplace.

The assessment conducted by Food Directorate evaluators determined how Clearfield™ rice varieties CL IMINTA 1 and CL IMINTA 4 were developed; how their composition and nutritional quality compares to traditional rice varieties; and the potential for the presence of any toxicants, anti-nutrients, or allergens. BASF has provided data which demonstrates that Clearfield™ rice varieties CL IMINTA 1 and CL IMINTA 4 are as safe and nutritious as the conventional rice 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 rice varieties CL IMINTA 1 and CL IMINTA 4 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

  1. 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 rice lines CL IMINTA 1 and CL IMINTA 4 were developed from seeds treated with the mutagen sodium azide. These seeds were grown under greenhouse conditions to produce the M1 generation. The herbicide tolerant lines CL IMINTA 1 and CL IMINTA 4 were selected from the M3 generation based on parental type and tolerance to the imidazolinone herbicides imazapic and imazapir. These varieties of CL IMINTA rice have been generated using self pollination and are currently at the M7 generation. This process has been described by the petitioner and is similar to the process used in previously approved Clearfield™ submissions.

The target of the imidazolinone class of herbicides is the enzyme acetohydroxyacid synthase (AHAS) which is responsible for the first step in the biosynthesis of essential branched chain amino acids. Imidazolinone tolerance in Clearfield™ rice varieties CL IMINTA 1 and CL IMINTA 4 is due to a point mutation of a single nucleotide in the Als gene. This results in a single amino acid substitution in the expressed AHAS enzyme. The single amino acid change alters the binding site for the herbicide on the AHAS enzyme expressed by Als gene while having no effect on the normal functioning of the enzyme.

Characterization of the modified plant

The petitioner has provided sequencing data that characterized the nucleotide change, showing a single base change in the Als gene. This results in a single amino acid change in the AHAS enzyme confering resistance to imidazolinone herbicides. No change in the tolerance to imidazolinone herbicides has been observed over the M1 to M5 generations indicating that the trait is stable in the plant genome. The petitioner has stated that this has been confirmed through sequencing of Als clones at the M6 and M7 generations.

The petitioner has also provided information regarding the functionality of the mutant AHAS protein as compared to this wild type counterpart. Data from these studies indicate that the mutant protein is not significantly different in trypsin, heat or feedback inhibition from the wild type.

Product information

Rice varieties CL IMINTA 1 and CL IMINTA 4 differ from their traditional counterparts in that they are tolerant to Imidazolinone herbicides. This is due to a mutation in the AHAS enzyme produced by Als. A mutation in the AHAS enzyme in rice could affect the biosynthesis of the essential amino acids isoleucine, leucine, and valine. The amino acid composition of Clearfield™ rice varieties CL IMINTA 1 and CL IMINTA 4 was compared to their parent, confirming that the AHAS activity of the imidazolinone-tolerant wheat was not affected by the mutation.

Dietary exposure

Rice varieties CL IMINTA 1 and CL IMINTA 4 are expected to be used in similar application as traditional rice varieties by the food industry.


Nutrient and antinutrient data were provided to the Food Directorate for the evaluation of CL IMINTA 1 and CL IMINTA 4 rice grain. A randomized complete block design with three replications (at each of the two locations in Argentina) of each variety (i.e., two test varieties: CL IMINTA 1 and 4, and one parent variety: IRGA 417) was used to obtain their compositional data. Compositional analyses were conducted on the grain samples, using accepted methods. Samples were analyzed for proximates (moisture, crude fat, crude fibre, protein, crude ash), 18 amino acids, 33 fatty acids (of which 5 were present at levels above the detection limit of 0.011%), seven minerals (phosphorus, zinc, magnesium, iron, copper, manganese and potassium), seven vitamins (thiamine, niacin, pantothenic acid, pyridoxine, total tocopherols, vitamin B2 and folic acid), and two antinutrients (phytic acid and trypsin inhibitor). Additional nutritional data from conventional rice varieties provided by the petitioner were obtained from the OECD Consensus document on compositional considerations for new varieties of rice (Oryza sativa) (2004).

The compositional data provided by the petitioner for these two rice varieties are acceptable and have been obtained using an acceptable study design, and valid sampling, analytical and statistical methodologies. Small but statistically significant differences in crude fat, oleic acid, and pantothenic acid were reported. The levels of these components were not outside of the range observed for conventional rice.

The data demonstrated that the levels of nutrients and antinutrients in grain from CL IMINTA 1 and CL IMINTA 4 rice were comparable with levels in grain from the parental variety IRGA 417. The petitioner has demonstrated that the two CLEARFIELD™ rice varieties are equivalent to the parental control variety. The use of the two CLEARFIELD™ rice varieties CL IMINTA 1 and CL IMINTA 4 will not impact the nutritional quality of the Canadian food supply.


The weight of evidence suggests that the AHAS protein expressed in CL IMINTA rice is unlikely to have toxic or allergenic properties. Systemic exposure to the intact mutant AHAS protein is negligible since the protein is present in low amounts in the edible portion of the rice, its activity is heat-labile and would be destroyed during cooking, or removed during processing in the production of edible oil.

The mutant AHAS protein is not homologous to known allergens or toxins, nor does it display characteristics of known food allergens. Furthermore, CL IMINTA rice does not express any new proteins or altered amounts of other proteins, which would include endogenous rice allergens.


Health Canada's review of the information presented in support of the food use of imidazolinone tolerant rice varieties CL IMINTA 1 and CL IMINTA 4 does not raise concerns related to food safety. Health Canada is of the opinion that food derived from rice varieties CL IMINTA 1 and CL IMINTA is as safe and nutritious as food from current commercial rice varieties.

Health Canada's opinion deals only with the food use of imidazolinone tolerant rice varieties CL IMINTA 1 and CL IMINTA. 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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