Plants > Biotechnology / PNTs > Unconfined Release > Decision Documents Decision Document DD96-10:
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Pioneer Hi-Bred International Inc. (Pioneer) has developed a corn hybrid, 3751IR, which is tolerant to an imidazolinone herbicide. This hybrid was derived from an inbred line, XA17, that was selected for tolerance to imidazolinone using plant tissue culture techniques.
Health Canada has determined that food derived from this corn is substantially equivalent to that derived from currently commercialized corn (June 27, 1995).
Pioneer has submitted data and information on the identity of 3751IR corn and characterization of the herbicide tolerance trait. Data from agronomic studies conducted in Canada and the United States, and data from proximate analyses were submitted. Pioneer has also submitted data from analyses of whole plant corn samples, taken from three sites in Canada, for levels of valine, leucine and isoleucine.
The Plant Biosafety Office of the Plant Health and Production Division, has reviewed the information submitted by Pioneer for the determination of environmental safety, in light of the assessment criteria described in the regulatory directive Dir94-08 Assessment Criteria for Determining Environmental Safety of Plants with Novel Traits:
The Feed Section of the Plant Health and Production Division, CFIA, has also reviewed the information submitted by Pioneer in light of the assessment criteria for determining safety and efficacy of livestock feed, as described in the regulatory directive Dir95-03 Guidelines for the Assessment of Livestock Feed from Plants with Novel Traits:
The biology of corn (Zea mays), described in Dir94-11, shows that unmodified plants of this species are not invasive of unmanaged habitats in Canada. Corn does not possess the potential to become weedy due to traits such as lack of seed dormancy, the non-shattering aspect of corn cobs, and the poor competitive ability of seedlings. No competitive advantage was conferred to 3751IR corn, other than tolerance to imidazolinone. The mutation of the ALS in 3751IR has not significantly affected the physiology of the plant, as demonstrated by the normal levels of valine, leucine and isoleucine. It is therefore not expected that 3751IR would possess traits that would render it invasive of unmanaged habitats.
Corn is an open-pollinated species and 3751IR could cross-pollinate with other corn hybrids. The resulting progeny could acquire the herbicide tolerance gene. Progeny from self-pollination will also be imidazolinone tolerant. Heterozygous progeny express herbicide tolerance, although at a lower level than homozygotes. Imidazolinone tolerant corn volunteers will thus appear in subsequent crops.
Corn volunteers are commonly found in soybean fields when soybeans are cultivated in the year following corn. Pursuit® (imazethapyr) is currently registered for use in soybeans and will not be effective in controlling 3751IR corn volunteers. Corn volunteers are usually at an immature growth stage at soybean harvest time resulting in problems during harvest operations. While these volunteers could be managed by mechanical means and other available herbicides, the present use of imidazolinone herbicides in soybeans may be compromised. In general terms, growers must be made aware that imidazolinone tolerant corn volunteers will not be controlled in subsequent crops when imidazolinones are used as the sole weed control tool.
NOTE: A longer term concern, if there is general adoption of several different crop and specific herbicide weed management systems, is the development of crop volunteers with novel tolerances to specific herbicides. This could result in the loss of the use of these herbicides in some crop rotation cycles. Agricultural extension personnel, in both the private and public sectors, should therefore promote careful management practices for growers who use any of these herbicide tolerant crops.
The above considerations, together with the fact that the novel trait has no intended effects on weediness or invasiveness, led CFIA to conclude that 3751IR corn does not possess altered weed or invasiveness potential compared to currently commercialized corn.
The biology of corn, as described in Dir94-11, indicates that there are no wild relatives in Canada that can freely hybridize with Zea mays. CFIA therefore concludes that gene flow from 3751IR corn to corn relatives is not possible in Canada.
The novel trait in this plant does not inherently confer to 3751IR any potential to become a plant pest and Zea mays is not a plant pest in Canada (Dir94-11). Agronomic traits were shown to be within the range displayed by currently commercialized corn hybrids and the mutation of the ALS in 3751IR has not significantly affected the physiology of the plant, as demonstrated by the normal levels of valine, leucine and isoleucine. This led CFIA to conclude that 3751IR corn does not display any altered pest potential.
The mutant ALS in this hybrid has not significantly affected the biosynthesis of the branched-chain amino acids, valine, leucine and isoleucine indicating that the metabolism of the plant has not been unintentionally altered to produce any allergenic or toxic compounds. Based on the above, CFIA has determined that the unconfined release of 3751IR corn, when compared to currently commercialized corn, will not result in significantly altered impacts on interacting organisms, including humans.
3751IR corn does not possess novel phenotypic characteristics which would extend its use beyond the current geographic range of corn production in Canada. Since corn does not outcross to wild relatives in Canada, there will be no transfer of novel traits to unmanaged environments.
CFIA has therefore concluded that the potential impact of 3751IR corn on plant biodiversity is therefore equivalent to that of currently commercialized corn varieties.
No statistically significant differences in nutritional composition, i.e., crude protein, crude fat and crude fibre, were noted between the whole seed of 3751IR and those of current commercial corn cultivars. Valine, isoleucine and leucine contents in whole plants of 3751IR were compared to that of its closest counterpart 3751 to determine whether acetolactate synthase (ALS) activity of the PNT was affected by the mutation. No statistically significant differences in content of these amino acids were noted. These results collectively demonstrate that the mutation of the ALS enzyme in 3751IR, did not likely result in any secondary effects impacting on the composition or nutritional quality of the cultivar. Accordingly, 3751IR was judged to be substantially equivalent to traditional corn varieties in terms of nutritional composition.
The parent plant Zea mays is not known for the production of anti-nutritional factors and the novel trait in 3751IR corn would not be expected to induce their synthesis.
Based on the review of data and information submitted by Pioneer Hi-Bred International Inc., and through comparisons of 3751IR with an unmodified Zea mays counterpart, the Plant Biosafety Office of the Plant Health and Production Division has concluded that the novel gene and its corresponding trait does not confer any intended or unintended ecological advantage to 3751IR following unconfined release.
Based on the review of submitted data and information, the Feed Section of the Plant Products Division has concluded that the novel trait does not in itself raise any concerns regarding the safety or nutritional composition of this line. Grain corn and several of its byproducts are currently listed in Schedule IV of the Feeds Regulations and are, therefore, approved for use in livestock feeds in Canada. As whole seeds and plants of 3751IR have been assessed and found to be substantially equivalent to traditional corn varieties, 3751IR and its byproducts are considered to meet the present definitions and are approved for use as livestock feed ingredients in Canada.
Unconfined release into the environment and use as livestock feed of 3751IR and other Z. mays lines derived from it, but not including those to which any other novel trait has been introduced, is therefore considered safe.
This bulletin is published by the Plant Health and Production Division. For further information, please contact the Plant Biosafety Office or the Feed Section at:
Plant Biosafety Office Plant Health and Production Division Plant Products Directorate 59 Camelot Drive, Nepean Ontario, K1A 0Y9 (613) 225-2342 |
Feed Section Animal Health and Production Division Animal Products Directorate 59 Camelot Drive, Nepean Ontario, K1A 0Y9 (613) 225-2342 |
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