<p style="text-align: justify;">As the development of DK404SR did not employ recombinant DNA technologies, this product was not subject to regulation in any jurisdiction except Canada, where it was regulated as a plant with novel trait under the <i>Seeds Act</i>, a novel feed under the <i>Feeds Act</i>, and as a novel food under the Food and Drug Regulations. Specific environmental, livestock feed, and food safety assessment of this product was only required for Canada.</p>

<p style="text-align: justify;">Only a small amount of whole maize kernel is consumed by humans. Maize oil is extracted from the germ of the maize kernel and maize is also a raw material in the manufacture of starch. A complex refining process converts the majority of this starch into sweeteners, syrups and fermentation products, including ethanol. Refined maize products, sweeteners, starch, and oil are abundant in processed foods such as breakfast cereals, dairy goods, and chewing gum.<br />
In the United States and Canada maize is typically used as animal feed, with roughly 70% of the crop fed to livestock, although an increasing amount is being used for the production of ethanol. The entire maize plant, the kernels, and several refined products such as glutens and steep liquor, are used in animal feeds. Silage made from the whole maize plant makes up 10-12% of the annual corn acreage, and is a major ruminant feedstuff. Livestock that feed on maize include cattle, pigs, poultry, sheep, goats, fish and companion animals.</p>

<p style="text-align: justify;">Industrial uses for maize products include recycled paper, paints, cosmetics, pharmaceuticals and car parts.</p>

<p style="text-align: justify;">The maize hybrid DK404SR was developed to allow the use of sethoxydim, the active ingredient in the herbicide Poast&reg;, for the control of annual and perennial grasses in maize crops. The original sethoxydim-tolerant mutant line (S2), which was the source of the sethoxydim tolerance trait in hybrid DK404SR, was selected as a somaclonal variant from maize embryo tissue grown under sethoxydim-selective pressure. The process involved growing somatic embryos on sethoxydim-enriched media in the presence of mutagenic agents. The somaclonal variant cell line S2 was selected from the resulting mutant cells and subsequently regenerated. This S2 line was backcrossed at least six times with both parental lines of the hybrid DK404SR to transfer the herbicide tolerance trait.</p>

<p style="text-align: justify;">Sethoxydim and other cyclohexanedione herbicides act by inhibiting the enzyme acetyl-CoA-carboxylase (ACCase), a key enzyme in the fatty acid biosynthesis pathway necessary for the synthesis and maintenance of membranes and for the incorporation of fatty acids into triacylglycerides. Inhibition of this enzyme results in a lethal disruption of lipid biosynthesis. Cyclohexanedione herbicides applied at rates recommended for effective weed control are toxic to conventional maize varieties. The ACCase present in DK404SR contains a mutation within the sethoxydim binding site that reduces the herbicide&rsquo;s affinity for the enzyme, and thus its inhibitory activity, while retaining the normal catalytic properties of the enzyme. The modified maize plants also demonstrated some level of cross-tolerance to the related herbicides, aryloxyphenoxypropionates, including haloxyfop (not registered in Canada), fluazifop (Venture&reg;) and quizalofop (Assure&reg;). These herbicides all have the same mode of action through ACCase inhibition. Natural tolerance to sethoxydim herbicide is found in several broad-leaved plants and grasses, including annual ryegrass, green foxtail and red fescue.</p>

<p style="text-align: justify;">As the development of DK404SR did not employ recombinant DNA technologies, this product was not subject to regulation in any jurisdiction except Canada, where it was regulated as a plant with novel trait under the Seeds Act, a novel feed under the Feeds Act, and as a novel food under the Food and Drug Regulations. Specific environmental, livestock feed, and food safety assessment of this product was only required for Canada.</p>

<p style="text-align: justify;">Field testing of DK404SR maize hybrids demonstrated that agronomic characteristics such as plant size and vigour, growth, male and female fertility, time to maturity, flowering period, and seed yield were within the range of values displayed by currently commercialized hybrids. It was determined that the growing habit of the modified maize plants was not inadvertently altered and that they did not exhibit weedy characteristics, or negatively affect beneficial or non-target organisms. DK404SR was not expected to impact on threatened or endangered species.</p>

<p style="text-align: justify;">Maize does not have any closely related species growing in the wild in Canada. Cultivated maize can naturally cross with annual teosinte (Zea mays ssp. mexicana) when grown in close proximity, however, these wild maize relatives are native to Central America and are not naturalized in North America. Additionally, reproductive and growth characteristics were unchanged in DK404SR. Gene exchange between DK404SR and maize relatives was determined to be negligible in managed ecosystems, with no potential for transfer to wild species in Canada.</p>

<p style="text-align: justify;">A food and livestock feed safety assessment of DK404SR compared the nutritional composition of the modified maize line to that of its unmodified counterparts, revealing no significant differences. The selection of the DK404SR maize hybrid through somaclonal variation had no meaningful effect on the maize plant nutrient levels. It was therefore determined that the use of maize products derived from the DK404SR maize hybrid would have no significant impact on the nutritional quality of the food supply in Canada.<br />
<br />
The novel trait in the DK404SR maize hybrid results from modifications of a single maize enzyme, altering the sethoxydim binding site without modifying the metabolic abilities of the ACCase enzyme. Potential toxicity of this enzyme was therefore not a concern. No new genetic material was introduced into the maize genome during the modification process, minimizing potential toxicity and allergenicity concerns.</p>
