<p style="text-align: justify;"><b>Field Testing</b></p>

<p style="text-align: justify;">These transgenic potatoes were field tested in the United States (1991-1994) and in Canada (1992-1995), and were compared to non-transgenic Russet Burbank for differences in physical characteristics, disease susceptibility, and insect susceptibility. The field data reports indicated no obvious differences in the number of volunteers, emergence from seed potatoes, percent stand (emergence), overwintering capacity, and tuber yield and quality. Susceptibilities to diseases, other than to CPB, including early blight, late blight, verticillium, potato leaf roll virus, and potato virus Y were unchanged. Field observations confirmed that Colorado potato beetle was controlled at all stages of development throughout the growing season and also indicated that potato flea beetles (Coleoptera: Chrysomelidae, <i>Epitrix cucumeris</i> Harris) were affected to some extent. Overall the field data reports and data on agronomic traits showed that the CPB-resistant potato lines had no potential to pose a plant pest risk.</p>

<p style="text-align: justify;"><b>Outcrossing</b></p>

<p style="text-align: justify;">In general, the natural exchange of genetic material is only possible with other varieties of potato <i>Solanum tuberosum</i>. Since the reproductive characteristics of the CPB-resistant potato lines were unchanged by the genetic modification, they should be no different than the parent cultivar &#39;Russet Burbank&#39;. Gene exchange between CPB-resistant potatoes and other Solanum species is very unlikely and is limited to cross-pollination with other potatoes.</p>

<p style="text-align: justify;">Gene transfer from CPB-resistant potato lines and other potato cultivars is limited. Multiple barriers, such as male sterility in the CPB-resistant potato lines derived from the male sterile cultivar &#39;Russet Burbank&#39;, prevent pollen production. Cross-pollination between CPB-resistant potatoes and male-fertile potato cultivars and subsequent seed production would be very unlikely due to limited pollen dispersal in potatoes. Should such an event occur, the resultant progeny must be male fertile in order for further introgression to occur.</p>

<p style="text-align: justify;">The chances for successful hybridization between transformed potato lines BT6, BT10, BT12, BT16, BT17, BT18, and BT23 and most wild relatives is extremely unlikely as potatoes (<i>Solanum tuberosum</i>) are unsuccessful in forming natural hybrids with the native or introduced weeds of Solanum species that do not bear tubers. In Canada there are no tuber producing wild relatives of Solanum. In the United States, tuber-bearing Solanum species include <i>S. jamesii</i>, <i>S. fendleri</i>, and <i>S. pinnatisectum</i>. However, the possibility of gene introgression is excluded due to constraints of geographical isolation and other biological barriers to natural hybridization. No natural hybrids have been observed between these species and cultivated potatoes.</p>

<p style="text-align: justify;"><b>Weediness Potential</b></p>

<p style="text-align: justify;">No competitive advantage was conferred to CPB-resistant potato lines, other than resistance to CPB, which will not, in itself, render potatoes weedy or invasive of natural habitats as none of the reproductive or growth characteristics have been modified.</p>

<p style="text-align: justify;">Potatoes do not exhibit weediness characteristics and have difficulty becoming established outside cultivated fields. Small tubers left in the ground after harvest (groundskeepers) may give rise to volunteer plants in the next crop but are usually killed by frost or drought. Surviving volunteers can be controlled with herbicides and cultivation. Furthermore, seed dispersal is limited as dissemination is by tuber and seed. Outside of cultivated areas, seedlings grown from true seed do not compete successfully and are not reported as a weed pest.</p>

<p style="text-align: justify;"><b>Secondary and Non-Target Adverse Effects</b></p>

<p style="text-align: justify;">The host ranges and habitats of the nine coleopteran insect species currently listed or proposed as threatened and endangered were examined to determine if CPB-resistant potatoes might have an adverse impact on these species. None of these species were found to inhabit potato fields or feed on potatoes, and they usually occurred in specialized habitats. For example, some of these insects (<i>i.e.</i>, the Kretschmarr Cave mold beetle and the Coffin Cave mold beetle) live in caves, and some (<i>i.e.</i>, northeastern beach tiger beetle and puritan tiger beetle) live on beaches.</p>

<p style="text-align: justify;">Other invertebrates, such as earthworms, and all vertebrate organisms, including non-target birds, mammals and humans, were not expected to be affected by the Cry3A insect control protein, because they do not contain the receptor protein found in the midgut of target insects.</p>

<p style="text-align: justify;">Dietary toxicity studies were performed using the 68 kDa microbial protein on beneficial insects (honeybee, ladybird beetle, green lacewing and parasitic wasp), and with eight non-target insect species representing the orders of Coleoptera, Diptera, Homoptera, Lepidoptera and Orthoptera (southern corn rootworm, yellow fever mosquito, green peach aphid, European corn borer, tobacco hornworm, corn earworm, tobacco budworm and German cockroach). No negative effects were observed, except for slightly higher mortality and reduced honeydew production of green peach aphids. Green peach aphids are major vectors of potato viruses, specifically of the potato leaf roll virus, and are chemically controlled in standard potato production systems. The effect of CPB-potatoes on these aphids was therefore negligible in terms of environmental impact.</p>

<p style="text-align: justify;">The density of insect populations was investigated. The following beneficial and predacious arthropods were significantly more abundant in the transgenic potato plots than in those treated with conventional chemical insecticides: big eyed bugs, damsel bugs, minute pirate bugs, some Hymenoptera spp. and spiders. As a result, aphid populations may be reduced through predation by natural enemies. Field observations also showed that populations of the detritivorous collembolans were as abundant in CPB-resistant potato fields as in fields of non-transgenic potato counterparts, and more abundant than in those treated with conventional chemical insecticides.</p>

<p style="text-align: justify;"><b>Impact on Biodiversity</b></p>

<p style="text-align: justify;">CPB-resistant potato lines have no novel phenotypic characteristics that would extend their use beyond the current geographic range of potato production. Since there is no occurrence of wild relatives of potato in Canada, there will be no transfer of novel traits to unmanaged environments. Similarly, as the risk of gene transfer to tuber-producing wild relatives in the United States is very remote, it was determined that the risk of transferring genetic traits from CPB-resistant potato lines to species in unmanaged environments was insignificant.</p>

<p style="text-align: justify;"><b>Other Considerations</b></p>

<p style="text-align: justify;">In order to prolong the effectiveness of plant-expressed <i>Bt</i> 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 <i>Bt</i>-expressing plants, including CBP-resistant potato lines, and require that growers plant a certain percentage of their acreage with non-transgenic varieties in order to reduce the potential for selecting <i>Bt</i>-resistant insect populations. Details on the specific design and requirements of individual IRM programs are published by the relevant regulatory authority.</p>
