Novel food information: Herbicide tolerant ExpressSunTM sunflower SU7

On this page

• Background
• Introduction
• Development of the modified plant
• Characterization of the modified plant
• Product information
• Dietary exposure
• Nutrition
• Chemistry/toxicology
• Conclusion

Background

Health Canada has notified Pioneer Hi-Bred Production Ltd. that it has no objection to the food use of herbicide tolerant ExpressSun^TM sunflower SU7 with an Als1 sulfonylurea herbicide 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 Pioneer Hi-Bred Production Ltd. and the evaluation by Heath Canada and contains no confidential business information.

Introduction

The imidazolinone tolerance trait in ExpressSun^TM sunflower SU7 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 sulfonylurea herbicides. Health Canada has previously indicated no objection to the sale of ALS mutagenized 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 ExpressSun^TM sunflower SU7 was developed; how its composition and nutritional quality compares to traditional sunflower varieties; and the potential for the presence of any toxicants, anti-nutrients, or allergens. Pioneer has provided data which demonstrates that ExpressSun^TM sunflower SU7 is as safe and nutritious as the conventional sunflower 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 ExpressSun^TM sunflower SU7 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. i. the plant, animal or microorganism exhibits characteristics that were not previously observed in that plant, animal or microorganism."

Development of the Modified Plant

Sulfonylurea tolerant ExpressSun^TM sunflower SU7 was developed using seed mutagenesis with ethylmethylsulfate (EMS) from the public sunflower variety HA89. Treated seeds were grown as the M1 generation to produce M2 seed. The M2 generation and each subsequent generation until M4 were screened for herbicide tolerance with a variety of sulfonylurea herbicides. This process has been fully described by the petitioner and resulted in the selection of a single line, designated SU7, as the preferred line for breeding purposes. The petitioner stated that ExpressSun^TM sunflower SU7 has been breed into elite sunflower lines and backcrossed for five generations.

The target of the sulfonylurea 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 ExpressSun^TM sunflower SU7 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 Als1 gene while having no effect on the normal functioning of the enzyme.

Characterization of the Modified Plant

The petitioner has provided data demonstrating that the mutation in ExpressSun^TM sunflower SU7 is identical to a mutation previously identified in the wild sunflower population. This mutation occurs in codon 197 of Als 1 in sunflower and results in tolerance to sulfonylurea herbicides.

The AHAS enzyme produced by this line has been shown to have similar activity to that produced by the parental line HA89. The mutation in the Als1 gene has been shown to be stably inherited in ExpressSun^TM sunflower SU7. This has been shown through consistent tolerance to imidazolinone herbicides in seven generations and through genotyping data generated from four generations. The petitioner has also presented data demonstrating that this trait is inherited in the expected Mendelian fashion.

Product Information

ExpressSun^TM sunflower SU7 differs from its traditional counterparts in that it is tolerant to sulfonylurea herbicides. This is due to a mutation in the AHAS enzyme produced by Als. A mutation in the AHAS enzyme could affect the biosynthesis of the essential amino acids isoleucine, leucine, and valine. The amino acid composition of ExpressSun^TM Sunflower SU7 was compared to its parent, confirming that the AHAS activity of the imidazolinone-tolerant sunflower was not affected by the mutation.

Dietary Exposure

ExpressSun^TM sunflower SU7 is expected to be used in similar applications as traditional sunflower varieties by the food industry.

Nutrition

Nutritional data was collected from a study conducted at four field sites located in the commercial sunflower-growing regions of the United States. The study was planned using randomized block design containing three replicates for each test and control varieties.

Whole seeds from test and control were analysed for proximates (moisture, crude protein, crude fibre, crude fat, carbohydrates and ash); amino acids (methionine, cystine, lysine, tryptophan, threonine, isoleucine, histidine, valine, leucine, arginine, phenylalanine, glycine, alanine, aspartic acid, glutamic acid, proline, serine, tyrosine); minerals (calcium, magnesium, manganese, phosphorus, potassium, copper, iron, zinc, selenium); vitamins (vitamin B₁, vitamin B₂, vitamin B₃, vitamin B₆, vitamin C, pantothenic acid, folic acid); and fatty acids (myristic acid, palmitic acid, palmitoleic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, arachidic acid, behenic acid, eicosenic acid and tetrasanic acid).

One sample for test and control from each site was also analyzed for tocopherols, phytosterols, fatty acids, metals, and physical parameters.

Most of the comparisons of the compositional data showed no significant difference between test and control treatments. For the analytes for which significant differences were observed, the values were within the reported literature range.

Chemistry/toxicology

The weight of evidence suggests that the mutagenized AHAS expressed in ExpressSun^TM sunflower SU7 is unlikely to demonstrate toxic or allergenic properties under usual conditions of consumption. No toxicological or allergenic concerns were introduced at the level of exposure to ALS in those products.

With regard to the oil produced from this mutant sunflower, extensive processing applied in refining of the oil would likely remove protein residues, and consequently exposure to any protein, including the mutated ALS protein or an endogenous allergen(s), is expected to be negligible. No increases in the level of heavy metals was observed in oil derived from this mutant sunflower compared to the non-mutated sunflower.

The concentration of major anti-nutrients were shown not be significantly different in the mutant as compared to non-mutant varieties of sunflower meal. The protein content and amino acid profile in the mutant compared to the non-mutant sunflower seed showed that no significant changes in the level of protein or amino acid profile were present in the mutant sunflower. This suggests that it is unlikely the novel sunflower contained increased amounts of endogenous allergens or large amounts of unintended novel proteins.

Conclusion

Health Canada's review of the information presented in support of the food use of sulfonylurea tolerant ExpressSun^TM sunflower SU7 does not raise concerns related to food safety. Health Canada is of the opinion that food derived from ExpressSun^TM sunflower SU7 is as safe and nutritious as food from current commercial sunflower varieties.

Health Canada's opinion deals only with the food use of sulfonylurea tolerant ExpressSun^TM sunflower SU7. Issues related to growing ExpressSun^TM sunflower SU7 in Canada and 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
bmh-bdm@hc-sc.gc.ca