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 2B : Imidazolinone tolerance in PM1 and PM2 canola

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: Brassica napus PM1 and PM2
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) cultivated* 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, and the trait had not previously been authorized by the PBO for use in a plant of the same species. 

References:

* The Plant Biosafety Office interprets "cultivated" to mean "grown by an individual as a crop." This means that seed multiplication plots and breeding lines are considered "cultivated."

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: 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, and the trait had not previously been authorized by the PBO for use in a plant of the same species. 

References:

2a.  Weediness potential: Is there an increased potential that the plant will become a weed of agriculture or be invasive in the Canadian environment? No – All commercial canola varieties are naturally tolerant to the ethametsulfuron methyl herbicide MUSTER® (DuPont), which also targets the ALS gene family, and these do not show invasive characteristics.  Plants with this trait do not 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 can be controlled using those or through mechanical means. 

References:

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? NoBrassica napus is known to outcross with other plants of the same species, as well as close relatives (B. rapa, B. juncea, B. carinata, B. nigra, Diplotaxis muralis, Raphanus raphanistrum, Erucastrum gallicum). However, the trait would confer no competitive advantage outside of the managed ecosystems where imidazolinone herbicides are used.  Additionally, the genetic change that results in increased tolerance to imidazolinone herbicides has very likely occurred in the wild on numerous occasions; therefore, gene flow from cultivated planting of imidazolinone-tolerant canola will not introduce a trait to wild populations that is not already there at some level.  Within managed ecosystems, herbicide-tolerant hybrids can be controlled using other herbicides or through mechanical means.

References:

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 – The genetic change imparting imidazolinone tolerance is not known to be linked to any unusual susceptibility to pests or pathogens, and the history of safe use of imidazolinone-tolerant crops does not lead to any contrary conclusions.  These strains of canola do not contain transgenic sequences derived from plant pests.

References:

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 ALS 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 mode of action for imidazolinone tolerance is a well characterized and common genetic change that occurs spontaneously in many crop species.  Agronomic characteristics and nutritional composition are unchanged from the comparator lines.

References:

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 practices*?

No – These canola varieties have no phenotypic characteristics that would extend their use beyond the current geographic range of canola production in Canada.  Since outcross species are only found in disturbed habitats, transfer of the novel trait would not impact unmanaged environments.

Potentially – The natural occurrence of tolerance to ALS-inhibiting herbicides in the field has been reported for sulfonylurea (Guttieri et al. 1992) and imidazolinones (Schmitzer et al. 1993; Bernasconi et al. 1995), and there is the potential that widespread adoption of PM1 and PM2 canola could result in increased application of imidazolinone-containing herbicides and consequently, increased selection pressure on weed populations.  This could impact the long-term utility of ALS-inhibiting herbicides and prompts the need to consider appropriate crop/herbicide management practices to minimize potential negative impacts on weed control and the environment.

In light of this concern, consultation with the Plant Biosafety Office and further risk analysis is recommended.

No – These canola varieties have no phenotypic characteristics that would extend their use beyond the current geographic range of canola production in Canada.  Since outcross species are only found in disturbed habitats, transfer of the novel trait would not impact unmanaged environments.

Potentially –The natural occurrence of tolerance to ALS-inhibiting herbicides in the field has been reported for sulfonylurea (Guttieri et al. 1992) and imidazolinones (Schmitzer et al. 1993; Bernasconi et al. 1995), and there is the potential that widespread adoption of PM1 and PM2 canola could result in increased application of imidazolinone-containing herbicides and consequently, increased selection pressure on weed populations.  This could impact the long-term utility of ALS-inhibiting herbicides and prompts the need to consider appropriate crop/herbicide management practices to minimize potential negative impacts on weed control and the environment.

In light of this concern, consultation with the Plant Biosafety Office and further risk analysis is recommended.

References:

Bernasconi, P., Woodworth, A.R., Rosen, B.A., Subramanian, M.V., and Siehl, D.L.  1995.  A naturally occurring point mutation confers broad range tolerance to herbicides that target acetolactate synthase.  J. Biol. Chem. 270: 17381–17385.

Guttieri, M.J., Eberlein, C.V., Mallory-Smith, C.A., Thill, D.C., and Hoffman, D.L.  1992.  DNA sequence variation in Domain A of the acetolactate synthase gene of herbicide-resistant and susceptible weed biotypes. Weed Sci. 40: 670–677.

Schmitzer, P.R., Eilers, R.J., and Czeke, C.  1993.  Lack of cross-resistance of imazaquin-resistant Xanthium strumarium acetolactate synthase to flumetsulam and chlorimuron.  Plant Physiol.103: 281–283.

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.

* The Plant Biosafety Office interprets "environmentally sustainable crop management practices" to mean "crop management practices that promote long-term maintenance of ecosystem components and functions for future generations."

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.

Due to the potential for negative impacts on weed management and environmental sustainability over the long term resulting from the introduction of this novel herbicide-tolerance trait into canola intended for cultivation in Canada, this product was submitted to the Plant Biosafety Office for risk analysis, in accordance with the Part V of the Seeds Regulations

A safety assessment concluded that this product did not pose greater risk to the Canadian environment than conventional canola, however it was noted in the decision document that "agricultural extension personnel, in both the private and public sectors, should promote careful management practices for growers who use these herbicide tolerant crops, to minimize the development of multiple resistance."

Note:  This product was authorized for unconfined environmental release prior to the adoption of a PBO policy requiring submission and publication of stewardship plans for all herbicide-tolerant PNTs.

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