No competitive advantage was conferred to D404SR corn hybrids, other than tolerance to sethoxydim and cross-tolerance, to various degrees, to certain related herbicides of the same class. Tolerance to these herbicides will not, in itself, render corn weedy or invasive of natural habitats since none of the reproductive or growth characteristics were modified. All commercial broadleaved crop kinds are naturally tolerant to sethoxydim and there is no correlation with invasiveness characteristics. The resulting progeny could acquire the herbicide tolerance gene. Progeny from self-pollination of DK404SR will also be sethoxydim tolerant.
Heterozygous progeny express herbicide tolerance, although at a lower level than homozygotes.
Sethoxydim 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. While these volunteers could be managed by mechanical means and other available herbicides, the use of sethoxydim and, to a lesser extent, of the related herbicides fluazifop and quizalofop to control volunteer corn in soybean may be compromised. The above considerations led AAFC to conclude that D404SR hybrids have no altered weed or invasiveness potential compared to currently commercialized corn hybrids. Please note however that there is growing concern, with the adoption of several herbicide tolerant corn varieties, that various corn volunteers with different novel herbicide tolerances could become difficult to control in crop rotation cycles.