Outcrossing
Since pollen production and viability were unchanged by the genetic modification resulting in MON80100, pollen dispersal by wind and outcrossing frequency should be no different than for other maize varieties. Gene exchange between MON80100 and other cultivated maize varieties will be similar to that which occurs naturally between cultivated maize varieties at the present time. In Canada and the United States, where there are few plant species closely-related to maize in the wild, the risk of gene flow to other species is remote. Cultivated maize, or maize, Zea mays L. subsp. mays, is sexually compatible with other members of the genus Zea, and to a much lesser degree with members of the genus Tripsacum.
Weediness Potential
No competitive advantage was conferred to MON80100, other than that conferred by resistance to European corn borer. Resistance to ECB will not, in itself, render maize weedy or invasive of natural habitats since none of the reproductive or growth characteristics were modified. Cultivated maize is unlikely to establish in non-cropped habitats and there have been no reports of maize surviving as a weed. Maize volunteers are not uncommon but are easily controlled using herbicides or mechanical means. Zea mays is not invasive and is a weak competitor with very limited seed dispersal.
Secondary and Non-Target Adverse Effects
The history of use and literature suggest that the bacterial Bt protein is not toxic to humans, other vertebrates, and beneficial insects. The Bt protein expressed in MON80100 maize (Cry1Ab) was shown to be equivalent to the original microbial protein. This protein is active only against specific lepidopteran insects and no lepidopteran species are listed as threatened or endangered species in Canada or the United States.
Maize inbreds and hybrids expressing the Cry1Ab protein were compared to their non-transformed counterpart for relative abundance of beneficial arthropods. Field studies demonstrated that Cry1Ab had neither a direct nor an indirect effect on the beneficial arthropod populations.
Numerous dietary studies assessed the potential toxicity of the Cry1Ab trypsin-resistant core protein on several nontarget organisms. A protein concentration greater than 10 times the amount that killed target Lepidoptera had no visible effect on honey bees (Apis mellifera L.) or their larvae. Larvae of green lacewing (Chrysopa carnea), a beneficial predatory insect, were not adversely effected when fed moth eggs for seven days that were coated with about eight times the concentration (16.7 ppm) of Cry1Ab core protein that kills ECB. When parasitic hymenoptera, Brachymeria intermedia, which is a beneficial parasite of the housefly (Musca domestica), were exposed to ten times the concentration of activated Cry1Ab protein that kills ECB (20 ppm in honey/water solution) for thirty days there were no treatment-related mortality or signs of toxicity. Similar studes were conducted on Ladybird beetles (Hippodamia convergens), a beneficial predaceous insect which feeds on aphids and other plant insects commonly found on stems and foliage of weeds and cultivated plants. Ladybird beetles exposed to activated Cry1Ab protein at a test concentration of 20 ppm in a honey/water solution for nine days did not exhibit treatment related mortality or signs of toxicity.
A bird study on quails was conducted to assess the wholesomeness of insect protected maize meal fed to quail since birds may feed on maize left in the field after harvest. No mortality occurred in birds fed up to 10% (nominal 100,000 ppm) raw maize seed meal in their diet. Consumption of diet containing 10% of the diet on weight basis of raw maize meal is equivalent to the quail eating 138 seeds/kg body weight per day. The seeds contained 0.57 ppm of the Cry1Ab protein.
In summary, it was determined that when compared with currently commercialized maize varieties, MON810 maize did not present an increased risk to or impact on interacting organisms, including humans, with the exception of specific lepidopteran insect species. It was also concluded that there was no reason to believe that deleterious effects or significant impacts on nontarget organisms, including beneficial organisms, would result from the EPSPS encoding and gox genes used as selectable markers during development of MON80100.
Impact on Biodiversity
MON80100 has no novel phenotypic characteristics that would extend its use beyond the current geographic range of maize production. Since the risk of outcrossing with wild relatives in Canada and the United States is remote, it was determined that the risk of transferring genetic traits from MON80100 maize to species in unmanaged environments was not significant.
Other Considerations
In order to prolong the effectiveness of plant-expressed Bt toxins, and the microbial spray formulations of these same toxins, regulatory authorities in Canada and United States have required developers to implement specific Insect Resistant Management (IRM) Programs. These programs are mandatory for all transgenic Bt-expressing plants, including MON80100 maize, and require that growers plant a certain percentage of their acreage to non-transgenic varieties in order to reduce the potential for selecting Bt-resistant insect populations. Details on the specific design and requirements of individual IRM programs are published by the relevant regulatory authority.
MON80100 maize plants are not likely to eliminate the use of chemical insecticides which are traditionally applied to about 25 to 35% of the total maize acreage planted, since the primary target for most of these applications has been the coleopteran, corn rootworm. MON80100 maize may positively impact current agricultural practices used for insect control by 1) offering an alternative method for control of European corn borer (and potentially other Cry1Ab-susceptible pests of maize); 2) reducing the use of insecticides to control European corn borer and the resulting potential adverse effects of such insecticides on beneficial insects, farm worker safety, and ground water contamination; and 3) offering a new tool for managing insects that have become resistant to other insecticides currently used or expressed in maize, including other Bt-based insecticides.
