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This Decision Document has been prepared to explain the regulatory decision reached under Dir94-08 Assessment Criteria for Determining Environmental Safety of Plants with Novel Traits and its companion document BIO2005-01 The Biology of Helianthus annuus L. (Sunflower) and Chapter 2.6 of the Regulatory Guidance: Feed Registration Procedures and Labelling Standards, entitled «Guidelines for the Assessment of Novel Feeds: Plant Sources».
The Canadian Food Inspection Agency (CFIA) has evaluated information submitted by BASF Canada Inc.
in regard to the imidazolinone herbicide tolerant sunflower line CLHA-PLUS and CLsunflower hybridH4. The CFIA has sure that these plants with novel traits (PNTs) do not present altered environmental risk nor, as novel feeds, do they present livestock feed safety concerns when compared to currently commercialized sunflower varieties in Canada.
Taking into account these evaluations, unconfined release into the environment and use as livestock feed of line CLHA-PLUS, including lines derived from it as well as hybrids containing novel traits from CLHA-PLUS and line CLIMISUN (including CLsunflower hybridH4) are therefore authorized by the Plant Biosafety Office of the Plant Health and Biosecurity Directorate and the Animal Feed Division of the Animal Health Directorate, as of June 4, 2010.
Any sunflower lines or hybrids derived from line CLHA-PLUS may also be released into the environment and used as livestock feed, provided that (i) no inter-specific crosses are performed, (ii) the intended uses are similar, and (iii) it is known based on characterization, that these plants do not display any additional novel traits and are substantially equivalent to sunflowers currently grown in Canada, in terms of their potential environmental impact and livestock feed safety.
Sunflower line CLHA-PLUS and CLsunflower hybridH4 are subject to the same phytosanitary import requirements as their unmodified counterparts.
Please note, that the livestock feed and environmental safety assessments of novel feeds and PNTs are critical steps in the potential commercialization of these plant types.
Other requirements, such as the evaluation of food safety by Health Canada, own been addressed separately from this review.
IV. Criteria for the Environmental Assessment
Potential of sunflower hybrid H4 to Become a Weed of Agriculture or be Invasive of Natural Habitats
Sunflower production in Canada occurs in southern Manitoba, Saskatchewan and Alberta, with a extremely little quantity of production in Ontario. Cultivated sunflower does not own a high potential for weediness.
Sunflower plants can grow as volunteers in a cultivated field following a sunflower crop and are generally eliminated via cultivation or the use of herbicides. In the recent provincial weed surveys conducted in Manitoba (2002) and Saskatchewan (2003), volunteer sunflower was ranked the 66th and 85th most abundant weed, respectively, and the Prairie Weed Survey Report 2005 ranked «Sunflower species» (Helianthussp.) 95th out of 148species in terms of relative abundance.
According to the information provided by BASF Canada Inc., no competitive advantage was conferred to CLsunflower hybridH4 other than that conferred by tolerance to imidazolinone herbicides.
CLsunflower hybridH4 was tested at three locations in 2007 in the United States in areas representative of Canada’s sunflower growing regions. Agronomic characteristics were evaluated that encompass a wide range of characteristics indicative of the entire life cycle of the sunflower plant.
They included germination (including dormancy), seedling emergence, seedling vigour, days to flower, days to maturity, plant height, and yield. The results showed no significant differences between CLsunflower hybridH4 and the unmodified counterpart, and support a conclusion of phenotypic equivalence to currently commercialized sunflower varieties. It is therefore not expected that CLsunflower hybridH4 would possess traits that would render it invasive of natural habitats since none of the reproductive or growth characteristics were modified.
Imidazolinone tolerance in itself will not cause CLsunflower hybridH4 to become more weedy or invasive in managed habitats than non-modified H.annuus.
Imidazolinone-tolerant sunflower volunteers will not be controlled in subsequent crops if a Group 2 herbicide is used as the sole weed control tool. However, control of imidazolinone tolerant sunflower as a volunteer weed can readily be achieved by the use of herbicides with other modes of action (i.e. non-Group 2 herbicides) or by mechanical means. BASF Canada Inc. has provided the CFIA with a stewardship plan that describes appropriate strategies that will permit the management of CLsunflower hybridH4 volunteers (see Appendix1).
The above considerations own led the CFIA to conclude that CLsunflower hybridH4 and its parental line CLHA-PLUS will not become weedier or more invasive than currently commercialized sunflower varieties.
Potential Impact of CLsunflower hybridH4 on Non-Target Organisms
The AHAS enzyme is not a known toxin or allergen and is commonly found in a wide variety of plants and micro-organisms with a history of safe use.
It does not exhibit properties typical of protein allergens or toxins (e.g. it is not resistant to digestive degradation or heat treatment) and the protein lacks homology with any known toxins or allergens.
BASF Canada Inc. has provided information to protest that the two amino acid substitutions found in the CLsunflower hybridH4 AHAS enzyme do not change the nontoxic and nonallergenic properties of the plants’ AHAS protein. The functional activity of the protein is unaltered as well, and results of the compositional analysis of CLsunflower hybridH4 demonstrated that seed from this hybrid is as safe and nutritious as unmodified sunflower seed.
Therefore, no negative interactions with non-target symbiotic or consumer organisms are anticipated.
The CFIA has therefore sure that the unconfined release of CLsunflower hybridH4 or its parental line CLHA-PLUS will not result in altered impacts on non-target organisms, including humans, compared to current commercial sunflower hybrids.
Altered Plant Pest Potential of CLsunflower hybridH4
H.annuus is not a plant pest in Canada and the imidazolinone tolerance traits in CLsunflower hybridH4 are not expected to alter its plant pest potential. Numerous crop plants with mutations in the AHAS gene are cultivated in Canada and no instances of altered plant pest potential own ever been associated with these mutations. Furthermore, BASF Canada Inc.
observed the severity of an insect pest (the sunflower midge, Contarinia schulzi) and three pathogens (downy mildew (Plasmopara halstedii), rust (Puccinia helianthi), and sclerotinia (Sclerotinia sclerotiorum))in the agronomic field trials and identified no statistical or biological differences between CLsunflower hybridH4 and its unmodified counterparts.
The CFIA has therefore sure that CLsunflower hybridH4 and its parental line CLHA-PLUS do not present any concerns with honor to altered plant pest potential.
Potential for Gene Flow from CLsunflower hybridH4 to Wild Relatives Whose Hybrid Offspring May Become More Weedy or More Invasive
Canada is a centre of biodiversity for sunflower germplasm.
Wild Helianthus annuusL. is a native of North America, and Helianthus species are distributed widely across the Central Plains of Canada.
The wild H.annuus is a common roadside weed in the southern parts of the prairies, particularly in Manitoba. The cultivated and wild H.annuus own numerous opportunities for hybridization as they often grow in shut proximity. These populations overlap in flowering time and are visited by the same pollinators. Genetic cultivar markers are readily found in wild populations of H.annuus indicating no strong barrier to the introgression of domesticated germplasm into wild populations.
H.petiolaris, another annual species that occurs in pockets in Canada, has also been known to hybridize with H.annuus.
Several perennial species of genus Helianthus happen in Canada. The most conspicuous is H.maximiliani which flowers on the roadside in tardy summer and drop. H.giganteus occurs in pockets and H.tuberosus (Jerusalem artichoke) is found primarily on riverbanks. hybridization with these perennial species occurs extremely rarely in nature and artificial methods are generally required to cross H.annuus with these perennial species.
Gene flow from CLsunflower hybridH4 to wild H.annuus and H.petiolaris in Canada will happen, but it is not expected to result in increased invasiveness of the offspring.
The imidazolinone tolerance trait is not associated with enhanced weediness or competitiveness in the absence of the herbicide. The occurrence of imidazolinone tolerant wild sunflowers in agricultural fields will not cause greater weed management issues in comparison to wildtype wild sunflowers.
Imidazolinone herbicides are not widely used to control these weeds, and imidazolinone-tolerant wild sunflowers will still be easily controlled with herbicides with other modes of action (non-Group 2 herbicides) or cultivation. Imidazolinone herbicides are not used exterior of managed ecosystems and thus any wild H.annua or H.petiolaris with the imidazolinone-tolerance trait will not own a competitive advantage over these species without the trait.
Any new authorization of a PNT must take into account the spectrum of PNTs that own already been approved for unconfined environmental release in Canada.
Since there are no barriers to outcrossing within diverse varieties of cultivated H.annuus and wild H.annua or H.petiolaris, there is the possibility that novel trait of a previously authorized plant could become combined in volunteer sunflowers or in individuals in wild populations. Two sunflower PNTs own been previously authorized for unconfined environmental release in Canada. In CLsunflower hybridH4, BASF Canada Inc. has provided information to describe the environmental interactions between novel traits of a previously authorized hybrid X81359 and CLHA-PLUS. The combination of traits did not result in increased weediness or invasiveness of the hybrid in comparison to unmodified sunflower.
Based on familiarity with the other previously authorized trait (SU7), it is also unlikely that there will be increased weediness or invasiveness as a result of gene flow with CLsunflower hybridH4.
BASF Canada Inc. has provided the CFIA with a stewardship plan that describes appropriate strategies that will permit the deployment of cultivated sunflower lines expressing imidazolinone tolerance while minimizing volunteers and outcrossing to wild sunflowers (see Appendix1).
This stewardship plan also describes management strategies for the control of these plants should they appear in an agronomic situation. Additionally, the stewardship plans that own been provided by BASF Canada Inc. provide strategies for the management of volunteers or individuals in wild populations with both of the imidazolinone- and sulfonylurea-tolerance traits.
These plants will still be controlled by non-Group 2 herbicides and by non-chemical methods of control that control H.annuus.
Potential Impact of CLsunflower hybridH4 on Biodiversity
CLsunflower hybridH4 has no novel phenotypic characteristics which would extend its use beyond the current geographic range of sunflower production in Canada. Imidazolinone tolerance will not alter the ability of CLsunflower hybridH4 to persist in the Canadian environment. In addition, CLsunflower hybridH4 is not diverse from conventional sunflower in terms of safety to non-target organisms, weediness or plant pest potential.
The ability of CLsunflower hybridH4 to outcross is not expected to be altered either.
The herbicide tolerance trait could be linked to other domestic traits that could make the offspring of any hybrids less ‘fit’, which could then be increased in the population by selection with imidazolinone herbicides. However, imidazolinone herbicides are not used to control Helianthus species in unmanaged ecosystems, therefore, the genetic diversity of wild Helianthus species is not likely to change as any linked traits will not be selected. In managed ecosystems, the imidazolinone trait (and any linked traits) may be selected by imidazolinone herbicide use, but any hybrid offspring will be controlled by other weed management techniques.
The CFIA has therefore concluded that the impact on biodiversity of CLsunflower hybridH4 and its parental line CLHA-PLUS is equivalent to that of currently commercialized sunflower varieties.
BASF Canada Inc. has developed a sunflower hybrid tolerant to imidazolinone herbicides. This sunflower hybrid, designated CLsunflower hybridH4, was developed to permit in-crop applications of imidazolinone herbicides at normal field application rates. This will permit expanded use of post-emergent applications of imidazolinone herbicides in sunflower crops.
The CLsunflower hybridH4 was developed by conventionally breeding a previously approved imidazolinone-tolerant sunflower line (Clearfield™ Oilseed Sunflower hybrid X81359, also referred to as the CLIMISUN event; DD2005-50) with a new imidazolinone-tolerant line (CLHA-PLUS) in which the imidazolinone tolerance trait was introduced by mutagenesis.
The herbicide tolerance trait in CLHA-PLUS is conferred by a single point mutation in the acetohydroxyacid synthase (AHAS) gene such that this enzyme is no longer affected by imidazolinone herbicides.
BASF Canada Inc. intends to commercialize CLsunflower hybridH4, as well as sunflower lines with only the CLHA-PLUS event. The CFIA has sure that BASF Canada Inc.’s information regarding CLsunflower hybridH4 is also relevant to the determination of environmental safety and feed safety of the parental CLHA-PLUS line. This determination is based on the CFIA’s familiarity with the evaluation of PNTs and novel feeds with one or more modified AHAS genes in at least 9 diverse plant species, the nature of the two diverse mutations and their products, a safe history of cultivation in Canada of other products with single or dual mutations conferring imidazolinone herbicide tolerance, and that no environmental and feed safety concerns were identified with the CLsunflower hybridH4, which includes the CLHA-PLUS mutation.
BASF Canada Inc.
has provided data on the identity of CLsunflower hybridH4 and event CLHA-PLUS, a detailed description of the modification method and breeding history, information on the modified gene, the resulting protein and its mode of action and the stability of trait expression.
CLsunflower hybridH4 was field tested at three locations in the US in 2007, in regions representative of Canadian sunflower growing regions.
Agronomic characteristics and nutritional components were compared with the unmodified parental control hybrid H7 and two other unmodified sunflower varieties. Agronomic characteristics included germination (including dormancy), seedling emergence, seedling vigor, days to flower, days to maturity, plant height, and yield. Responses to biotic and abiotic stress tolerances were also observed. Nutritional components included proximates, fiber composition, amino acids, fatty acids, minerals, vitamins, and anti-nutrients
The Plant and Biotechnology Risk Assessment (PBRA) Unit of the Plant Health Science Directorate, CFIA, has reviewed the above information, in light of the assessment criteria for determining environmental safety of PNTs, as described in the Directive94-08 (Dir94-08), entitled «Assessment Criteria for Determining Environmental Safety of Plants With Novel Traits».
The PBRA Unit has considered:
- potential of CLsunflower hybridH4 and sunflower event CLHA-PLUS to become a weed of agriculture or to be invasive of natural habitats;
- potential impact of CLsunflower hybridH4 and sunflower event CLHA-PLUS or its gene products on non-target species, including humans; and
- potential for CLsunflower hybridH4 and sunflower event CLHA-PLUS to become a plant pest;
- potential for gene-flow from CLsunflower hybridH4 and sunflower event CLHA-PLUS to wild relatives whose hybrid offspring may become more weedy or more invasive;
- potential impact of CLsunflower hybridH4 and sunflower event CLHA-PLUS on biodiversity
The Animal Feed Division, CFIA, has also reviewed the above information with honor to the assessment criteria for determining the safety and efficacy of livestock feed, as described in Directive95-03 (Dir95-03), entitled «Guidelines for the Assessment of Novel Feeds: Plant Sources».
The Feed Section has considered:
- potential impact of CLsunflower hybridH4 and sunflower event CLHA-PLUS on livestock nutrition; and
- potential impact of CLsunflower hybridH4 and sunflower event CLHA-PLUS on livestock and workers/bystanders.
BASF Canada Inc. has provided the CFIA with a method for the detection and identification of sunflower products containing CLsunflower hybridH4 and sunflower event CLHA-PLUS.
III. Description of the Novel Trait
The CLsunflower hybridH4 was developed by conventional breeding between a CL IMISUN breeding line (described in DD2005-50) and a CLHA-PLUS breeding line.
Sunflower event CLHA-PLUS was developed by subjecting seeds of the sunflower line BTK47 to the mutagenic agent ethyl methanesulfonate (EMS). The plants derived from mutagenized seeds were treated with imidazolinone herbicides to identify imidazolinone tolerant events. After greenhouse and field evaluations of several mutant lines and generations for preferred characteristics, the CLHA-PLUS sunflower mutant was selected for further breeding.
Imidazolinone herbicides are athletic against the enzyme acetohydroxyacid synthase (AHAS), also known as acetolactate synthase (ALS).
AHAS is an enzyme found in bacteria, certain other micro-organisms and plants.
This enzyme catalyses the first step in the biosynthesis of the essential branched chain amino acids isoleucine, leucine and valine. Herbicide-induced AHAS inhibition results in a lethal decrease in protein synthesis. Unmodified sunflowers are not tolerant to imidazolinone herbicides.
BASF Canada Inc. provided data that demonstrated that CLsunflower hybridH4 contains two distinct mutations, each in diverse AHAS alleles, that confer imidazolinone tolerance. One of the mutations is from a previously authorized imidazolinone tolerant sunflower (Clearfield™ Oilseed Sunflower hybrid X81359, also known as the CLIMISUN trait).
The other mutation is from sunflower event CLHA-PLUS, which possesses a diverse mutation than that found in sunflower hybrid X81359. The single amino acid substitution in the AHAS gene of sunflower event CLHA-PLUS is sufficient to alter the binding site such that imidazolinone herbicides no longer bind to the AHAS enzyme, resulting in the herbicide tolerant phenotype for both CLHA-PLUS and the CLsunflower hybridH4.
The CLHA-PLUS imidazolinone tolerance trait is under the control of the native AHAS promoter and is believed to be constitutively expressed.
Sequence information for the modification in the AHAS gene was submitted.
The imidazolinone tolerance of the modified AHAS enzymes from CL sunflower H4 was demonstrated in vitro by comparison of the activity of the AHAS enzyme extracted from CLsunflower hybridH4 plants to that of imidazolinone-susceptible sunflower plants in presence of imidazolinone herbicides.
The single amino acid change in sunflower event CLHA-PLUS has previously been approved in BASF Canada Inc.’s Clearfield™ rice (varieties IMINTA 1 and 4) and Clearfield™ bread wheat (variety BW7).
AHAS proteins are not known toxins or allergens. Since the amino acid sequence of the mutated AHAS of sunflower event CLHA-PLUS differs by one amino acid from that of unmodified sunflower, no changes in allergenic or toxicological properties are anticipated for sunflower event CLHA-PLUS or CLsunflower hybridH4. Bioinformatic analysis confirmed the lack of homology between the amino acid sequence of sunflower event CLHA-PLUS AHAS protein and that of known or putative allergens or toxins.
The introduced mutation in sunflower event CLHA-PLUS is inherited as a partially dominant trait conferred by a single nuclear gene. Studies confirmed the Mendelian inheritance of the mutation and stable expression of the herbicide tolerance trait in event CLHA-PLUS across breeding generations.
The two mutations were stably inherited in breeding lines leading to CLsunflower hybridH4 as well. The mutation present in the CLHA-PLUS AHAS enzyme is therefore stable across generations.
I. Brief Identification of the Modified Plant
|Designation of the Modified Plant:||CLsunflower hybridH4 and parental line CLHA-PLUS|
|Applicant:||BASF Canada Inc.|
|Plant Species:||Sunflower (Helianthus annuus L.)|
|Novel Traits:||Tolerance to imidazolinone herbicides|
|Trait Introduction Method:||Chemically induced seed mutagenesis and conventional crossbreeding|
|Proposed Use of the Modified Plant:||Production of H.annuus for human food and livestock feed.|
Table of Contents
- Development Method
- Imidazolinone Tolerance
- Stable Expression
- Potential of sunflower hybrid H4 to Become a Weed of Agriculture or be Invasive of Natural Habitats
- Potential Impact of CLsunflower hybridH4 on Non-Target Organisms
- Altered Plant Pest Potential of CLsunflower hybridH4
- Potential for Gene Flow from CLsunflower hybridH4 to Wild Relatives Whose Hybrid Offspring May Become More Weedy or More Invasive
- Potential Impact of CLsunflower hybridH4 on Biodiversity
- Potential Impact of CLsunflower hybridH4 on Livestock Nutrition
- New Information Requirements
- Potential Impact of CLsunflower hybridH4 on Livestock and Workers/Bystanders
- Regulatory Decision