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Appendix 2: sample evaluations of the potential for new plant products to be regulated under Part V of the Seeds Regulations

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Appendix 2C : Imidazolinone tolerance in Clearfield™ sunflower hybrid X81359

PNT Determination Work Sheet
A companion document to Regulatory Directive 2009-09:
Plants with Novel Traits Regulated under Part V of the Seeds Regulations

Species: Helianthus annuus Clearfield™ Hybrid X81359
Trait: Imidazolinone tolerance, introduced through chemical mutagenesis of AHAS/ALS

1. Was the trait bred into the plant from, or present in, germplasm (of the same species) cultivatedFootnote 1 in Canada prior to 1996, or previously authorized by the PBO for use in a plant of the same species?

No – At the time that this product was developed, there was no evidence of this trait being present in germplasm of the same species cultivated in Canada.


If the answer to question 1 is "yes," then stop. The plant is not a PNT and is not subject to regulation under Part V of the Seeds Regulations. Otherwise, continue:

2. Does the plant have a potential to have a significant negative environmental impact, relative to an appropriate Canadian comparator line (or lines), in terms of:

2a. Weediness potential: Is there an increased potential that the plant will become a weed of agriculture or be invasive in the Canadian environment?

Yes, potentially – Cultivated sunflower does not have a high potential for weediness, but volunteers have been observed growing in cultivated fields. Plants with this trait would not be expected to have a competitive advantage over their comparator lines, other than that conferred by tolerance to imidazolinone. Any volunteer plants will be susceptible to non-imidazolinone herbicides, and could be controlled using those or through mechanical means.

The mutation of the AHAS gene does not affect the physiological, reproductive, or growth characteristics of the plant; therefore, it is not expected that this hybrid would possess traits that would render it invasive of natural habitats.

However, a longer term concern, if there is general adoption of several different crop and specific herbicide weed management systems, is the potential development of crop volunteers with a combination of novel resistances to different herbicides. This could result in the loss of the use of these herbicides and any of their potential benefits. A risk assessment should be completed and risk management options developed, if needed.


2b. Gene flow: Are there negative consequences to environmental safety resulting from the production of hybrids between the plant and any domestic or wild sexually compatible relatives that are present in Canada?

Yes, potentiallyHelianthus annuus L. is a native of North America, with wild relatives and other Helianthus species being distributed widely across the Central Plains of Canada from north to south. Wild H. annuus is a common roadside weed in the southern parts of the prairies, particularly in Manitoba, extending into the central United States. Cultivated and wild H. annuus have many opportunities for hybridization, as they often grow in close proximity in many locations. These species 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 been known to hybridize with H. annuus.

Several perennial species occur in Canada, the most conspicuous of which being H. maximiliani, which flowers on the roadside in late summer and early fall. Some H. giganteus occurs in pockets, as well as H. tuberosus (Jersualem artichoke), which is found primarily on riverbanks. This species has been cultivated to a small extent for its tubers. Hybridization with perennial species that are found in Canada occurs very rarely in nature, however, and artificial methods are required to cross H. annuus with these species.

Canada is a centre of biological diversity for Helianthus. Therefore, a risk assessment should be completed, to fully evaluate the impacts of gene flow to sexually compatible species; and risk management measures developed, if needed.


2c. Plant pest potential: Does the plant have increased potential to harbour and/or facilitate the spread of a pest or pathogen of the Canadian environment?

No – Hybrid X81359 would not be expected to have increased susceptibility to plant pests. No unusual or unexpected changes in pest potential (e.g. agronomic characteristics, pathogen interactions, and insect pest susceptibility) were observed in the development and field testing of this variety.


2d. Potential negative impacts on non-target organisms: Could the plant have negative impacts on non-target organisms interacting directly or indirectly with it, including humans as workers or bystanders?

No – The trait results from a single amino acid modification in the endogenous AHAS gene, does not modify the metabolic ability of the plant, and does not code for the production of a protein with characteristics that are typical of known allergens or toxins. The modified AHAS enzyme does not confer resistance to agricultural pests, and is commonly found in a wide variety of plants and microorganisms with a history of safe use.


2e. Other potential negative impacts on biodiversity: Does the plant have any other potential negative impacts on biodiversity, including changes to environmentally sustainable crop management practicesFootnote 2?

No – Hybrid X81359 has no novel phenotypic characteristics which would extend its use beyond the current geographic range of sunflower production in Canada. Reponses of hybrid X81359 to common insect pests and fungal pathogens are within the range of typical commercial sunflower cultivars. While cultivated sunflower is capable of outcrossing under natural conditions to wild relatives in Canada, the transfer of novel traits to other plant species in unmanaged environments is highly unlikely to have an impact on biodiversity. Therefore, the impact on biodiversity of this line is likely to be equivalent to that of currently commercialized sunflower lines.


If the answer to any part of question 2 is "yes" or is unclear, then contact the Plant Biosafety Office: the plant may be a PNT and may be regulated under Part V of the Seeds Regulations.

Please note: Depending on the product, data requirements for some criteria may be more extensive than others. Evidence, such as experimental data or peer-reviewed literature, should be available to support the rationale provided in this document.
The PBO reserves the right to request that more extensive data be supplied in support of a determination or to confirm the determination by the proponent.

Conclusion: This plant is a PNT and is regulated under Part V of the Seeds Regulations.

Because of the potential for concerns related to the impact on integrated weed management and the presence of several sexually compatible close relatives in the Canadian environment, this product was notified to the PBO.

A risk assessment was completed and this product was authorized for unconfined environmental release in 2005, on the condition that a herbicide tolerance stewardship plan be followed in order to address the concerns mentioned above.

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