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Decision Document 97-20:
Determination of the Safety of NatureMark Potatoes' Colorado Potato Beetle (CPB) Resistant Potato (Solanum tuberosum L.) Lines ATBT04-6, ATBT04-27, ATBT04-30, ATBT04-31 and ATBT04-36

This Decision Document has been prepared to explain the regulatory decision reached under the guidelines Dir94-08 Assessment Criteria for Determining Environmental Safety of Plants with Novel Traits and its companion document T-1-09-96 The Biology of Solanum tuberosum L. (potato) and the guidelines Dir95-03 Guidelines for the Assessment of Plants with Novel Traits as Livestock Feed.

The Canadian Food Inspection Agency (CFIA), specifically the Plant Biosafety Office of the Plant Health and Production Division and the Feed Section of the Animal Health and Production Division, and advice from the Pest Management Regulatory Agency, Health Canada, has evaluated information submitted by NatureMark Potatoes, a business unit of Monsanto, regarding five transformed potato lines referred to as NewLeaftm Atlantic potatoes in the present document. The plants were transformed with genes conferring resistance to the Colorado potato beetle (CPB), a major pest of potato in Canada, and resistance to kanamycin as a selectable marker. These genes are identical to those present in the NewLeaftm Atlantic potatoes previously authorized for release (please see DD96-06). CFIA has determined that these plants with novel traits should not pose concern to environmental safety and are considered to be substantially equivalent to potatoes currently approves as livestock feed. NatureMark Potatoes has developed and will implement a CPB resistance management plan.

Unconfined release into the environment, including feed use of the NewLeaftm Atlantic potato lines ATBT04-6, ATBT04-27, ATBT04-30, ATBT04-31, ATBT04-36 is therefore authorized. Also, any S. tuberosum lines derived from them, or resulting from the same transformation event, may be considered substantially equivalent, provided it is known following thorough characterization that: no inter-specific crosses are performed; the intended use is similar; these plants do not display any additional novel traits; and the understood pest resistance management plan summarized in this document is applied.

Please note that, while determining the livestock feed and environmental safety of plants with novel traits are critical steps in the commercialization of these plant types, other requirements still need to be addressed, such as Variety Registration (CFIA).

Table of Contents

1. Brief Identification of the Plants with Novel Traits (PNT's)
2. Background Information
3. Description of the Novel Traits
   1. Resistance to the Colorado Potato Beetle (CPB)
   2. Kanamycin Resistance
   3. Development Method
   4. Stable Integration into the Plants' Genomes
4. Assessment Criteria for Environmental Safety
   1. Potential of the PNT's to Become Weeds of Agriculture or Be Invasive of Natural Habitats
   2. Potential for Gene Flow to Wild Relatives Whose Hybrid Offspring May Become More Weedy or More Invasive
   3. Altered Plant Pest Potential
   4. Potential Impact on Non-Target Organisms
   5. Potential Impact on Biodiversity
   6. Potential for Development of CPB Resistance to the PNT's
5. V. Nutritional Assessment Criteria as Livestock Feed
   1. Anti-Nutritional Factors
   2. Nutritional Composition of the PNT's
6. Regulatory Decision

I. Brief Identification of the Plants with Novel Traits (PNT's)

II. Background Information

Monsanto has developed five potato lines resistant to Colorado potato beetle (CPB), the most important insect pest of potato in Canada. These potato lines, referred to as NewLeaftm Atlantic potatoes (lines ATBT04-6, ATBT04-27, ATBT04-30, ATBT04-31, ATBT04-36) in the present document, will provide an alternative for season-long control of larval stages and adults of CPB, thus resulting in a potential reduction of chemical foliar insecticide sprays.

The development of the NewLeaftm Atlantic potato lines was based on recombinant DNA technology, by the introduction of two bacterial genes into the potato variety "Atlantic." A gene conferring resistance to CPB was inserted, coding for an insecticidal protein active against a narrow range of Coleoptera. Another gene, conferring resistance to kanamycin, was also inserted; this gene is of no agronomic interest but was used to select modified plants from those that remained unmodified at the development stage.

These lines have been tested in Canada under confined conditions in 1995 (New Brunswick) and 1996 (New Brunswick, Prince Edward Island, Ontario, Alberta). Health Canada has determined that food derived from these potatoes is substantially equivalent to that derived from currently commercialized potatoes (November 1996).

Monsanto has provided data on the identity of NewLeaftm Atlantic potatoes, a description of the modification method, data and information on the gene insertion sites, copy numbers and levels of expression in the plant, the role of the inserted genes and regulatory sequences in donor organisms, and full nucleotide sequences.

The novel proteins were identified, characterized, and compared to the original bacterial proteins. Relevant scientific publications were also used as reference material.

Agronomic characteristics such as emergence, plant vigour, plant height, leaflet shape, stem count, uniformity and vigour, were compared to those of unmodified potato counterparts. The nutritional composition, including total solids, protein, fat, fibre, vitamin C content and sugar content as well as the production of toxicant glycoalkaloids was compared to that of the unmodified potato lines.

The potential development of CPB resistance to the insecticidal protein was acknowledged, and an insect resistance management plan will be implemented by NatureMark Potatoes, a business unit of Monsanto.

The Plant Biosafety Office of the Plant Health and Production Division, has reviewed the above information, in light of the following assessment criteria for determining environmental safety of plants with novel traits, as described in the regulatory directive Dir94-08. We have considered:

• potential of the PNT's to become weeds of agriculture or to be invasive of natural habitats,
• potential for gene-flow to wild relatives whose hybrid offspring may become more weedy or more invasive,
• potential for the PNT's to become plant pests,
• potential impact of the PNT's or their gene products on non-target species, including humans, and
• potential impact on biodiversity.

CFIA has consulted with the Pest Management Regulatory Agency of Health Canada on issues related to potential development of CPB populations resistant to the insecticidal protein produced by the PNT's.

The Feed Section of the Animal Health and Production Division, CFIA, has also reviewed the above information in light of the assessment criteria for determining safety and efficacy of livestock feed, as described in Dir95-03. We have considered:

• potential impact to livestock, and
• potential impact to livestock nutrition.

III. Description of the Novel Traits

1. Resistance to the Colorado Potato Beetle (CPB)

• Bacillus thuringiensis subsp. tenebrionis (B.t.t.) is a common gram-positive soil-borne bacterium. In its spore forming stage, it produces several insecticidal crystal Cry3A ð-endotoxins that are non-toxic to humans, other vertebrates, and beneficial insects. These proteins are used as environmentally acceptable foliar insecticides against CPB.
• The CPB resistance gene engineered into NewLeaftm Atlantic potatoes codes for one of these insecticidal crystal proteins, active against specific Coleoptera such as CPB, elm leaf beetle and yellow mealworm. Insecticidal activity results from the Cry3A protein binding to specific insect gut epithelium receptors, pore formation, loss of cations, and disruption of digestive processes following an osmotic pressure imbalance. Current knowledge indicates that only sensitive insects possess such receptors.
• The cry3A gene is linked to a light activated promoter. Protein production (referred to as B.t.t. protein in the present document) was quantified for the five lines and found to average from 15.7 to 59.3 µg/g (f.w.) of leaf tissue and from 0.09 to 0.53 µg/g (f.w.) of tuber tissue, corresponding to 0.10 to 0.37% of total foliage protein and 0.0004 to 0.003% of total tuber protein (assuming protein levels of 1.6% in leaves and 2% in tubers, f.w.). These expression levels correspond to a two fold increase in leaves and a four fold decrease in tubers, compared to the NewLeaftm Russet Burbank potatoes previously authorized for release (please see DD96-06). Foliage expression levels were highest at six weeks and gradually decreased over the season.
• The resulting B.t.t. proteins include a 68 kDa protein and a major proteolytic fragment of 55 kDa. A similar 55 kDa protein is also released in some B.t.t. registered microbial insecticides, and following tryptic digestion of the bacterial B.t. Cry3A protein purified from Escherichia coli.
• Western blot data was presented which showed that the 68 kDa and 55 kDa proteins expressed by B.thuringiensis, the Russet Burbank NewLeaftm potato and the Atlantic NewLeaftm potato had the same immunological reactivity and molecular weight. Data, previously submitted for the Russet Burbank NewLeaftm potato, showed the proteins had not been glycosylated or undergone other post translational modification and possessed similar bioactivity and host range specificity to the native protein.
• Studies have shown that B.t.t. proteins were rapidly inactivated when subjected to typical mammalian acidic stomach conditions, i.e. in simulated gastric fluids. Aerobic soil degradation of the B.t.t. proteins was shown to be complete after nine hours.
• The gene nucleotide sequence and the amino acid sequence were provided. A search for amino acid sequence similarity between the B.t.t. proteins and known allergens, using a database assembled from the public domain databases GenBank, EMBL, Pir and SwissProt, revealed no significant amino acid sequence homologies.

2. Kanamycin Resistance

• Kanamycin is an aminoglycosidic antibiotic that binds to bacterial ribosomes thus disrupting normal protein synthesis and killing the bacterial cell.
• The kanamycin-resistance gene, isolated from the bacterium E. coli, codes for an enzyme that phosphorylates kanamycin, thereby preventing it from binding to ribosomes and rendering the cells resistant.
• The gene is linked to a constitutive promoter. The average expression levels for all five lines were estimated to range from 4.4 to 36.6 µg/g (f.w.) of leaf tissue, and from 0.5 to 2.9 µg/g (f.w.) of tuber tissue, corresponding to 0.028-0.23% of foliage protein and 0.0025-0.014% of tuber protein (assuming protein levels of 1.6% in leaves and 2% in tubers, f.w.).
• The expressed NPTII protein was compared to the bacterial protein, and shown to be of similar molecular weight, indicating that there were no insertional or post- transcriptional modifications.
• This protein is ubiquitous in the environment. It degrades rapidly in vitro in simulated mammalian gastric and intestinal fluids.
• The nucleotide sequence showed no significant homology with the toxins or allergens entered in the GENEBANK DNA database.
• The full nucleotide sequence and corresponding amino acid sequence were provided.

3. Development Method

• Atlantic potatoes were transformed using a disarmed non-pathogenic Agrobacterium tumefaciens vector; the vector contained the transfer DNA (T-DNA) region of an Agrobacterium plasmid from which virulence and plant disease-causing genes were removed, and replaced with genes coding for CPB resistance and kanamycin resistance. The T-DNA portion of the plasmid is known to insert randomly into the plant's genome and the insertion is usually stable, as was demonstrated in these NewLeaftm Atlantic potatoes.

4. Stable Integration into the Plant's Genome

• The data provided showed various integration patterns depending on the line: the T- DNA was integrated at three sites for line ATBT04-6 and at one site for lines ATBT04-30 and ATBT04-31. No coding region from outside the T-DNA borders was incorporated into the genotype of these lines. Two complete copies of the T-DNA were found at two insertion sites in line ATBT04-27, with one site also containing a bacterial gene coding for resistance to streptomycin and an other partial copy of the cry3A gene. The streptomycin resistance gene is driven by a bacterial promoter and is not expressed in plants, as was demonstrated in these NewLeaftm Atlantic potatoes. Finally, the transgenes were integrated at three insertion sites in line ATBT04-36, with one of the sites containing the whole A. tumefaciens plasmid.
• The transformed plants were propagated vegetatively, and CPB resistance was expressed for at least three vegetative generations.

IV. Assessment Criteria for Environmental Safety

1. Potential of the PNT's to Become Weeds of Agriculture or Be Invasive of Natural Habitats

CFIA evaluated data submitted by NatureMark Potatoes on the reproductive and survival biology of NewLeaftm Atlantic potato lines, and determined that emergence, maturity, plant height, shape, stem count, uniformity and vigour, were within the normal range of expression currently displayed by commercial varieties. NewLeaftm Atlantic lines have no specific added genes for cold tolerance or winter hibernation.

The biology of Solanum tuberosum, described in T-1-09-96, shows that unmodified plants of this species are not invasive of unmanaged habitats in Canada. According to the information provided by NatureMark Potatoes, NewLeaftm Atlantic lines were determined not to be different from their counterparts in this respect.

No competitive advantage was conferred to NewLeaftm Atlantic lines, other than that conferred by resistance to Colorado potato beetles. Resistance to CPB will not, in itself, render potatoes weedy or invasive of natural habitats, since the typical vegetative reproductive characteristics of potatoes were not modified. The background genotype of these NewLeaftm Atlantic lines is Atlantic, a fertile variety that may produce seeds, however little berries and seeds are produced. Although limited dispersal is possible through dispersal of tubers, volunteers would not persist under ordinary cultivation conditions or in unmanaged habitats.

The above considerations, together with the fact that the novel traits have no intended effects on weediness or invasiveness, led CFIA to conclude that NewLeaftm Atlantic potatoes have no altered weed or invasiveness potential compared to currently commercialized potato varieties.

2. Potential for Gene Flow to Wild Relatives Whose Hybrid Offspring May Become More Weedy or More Invasive

The biology of potato, described in T-1-09-96, shows that there are no wild relatives in Canada that can naturally hybridize with S. tuberosum.

CFIA therefore concludes that gene flow from NewLeaftm Atlantic lines to potato relatives is not possible in Canada.

3. Altered Plant Pest Potential

The intended effects of both novel traits are unrelated to plant pest potential, and potato is not a plant pest in Canada. In addition, agronomic characteristics of NewLeaftm Atlantic lines, such as emergence, maturity, plant height and shape, stem count, uniformity and vigour, were shown to be within the range of values displayed by currently commercialized potato varieties.

CFIA has therefore determined that there is no reason to believe that NewLeaftm Atlantic lines would display any altered pest potential.

4. Potential Impact on Non-Target Organisms

Submitted data showed that he novel proteins produced in lines ATBT04-06, ATBT04-27, ATBT04-30, ATBT04-31 and ATBT04-36 were equivalent to those produced by the NewLeaftm Russett Burbank potatoes previously authorized for release in Canada (please see DD96-06). Therefore, any potential environmental impact resulting from the release of these lines will be no different from that of the NewLeaftm Russett Burbank potatoes. Colorado potato beetle, the target insect, was controlled in NewLeaftm potato plots at all stages of development throughout the growing season. Field observations indicated that potato flea beetles (Coleoptera: Chrysomelidae, Epitrix cucumeris Harris) were also affected by these potatoes to some extent.

The following beneficial and predacious arthropods were significantly more abundant in NewLeaftm 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 NewLeaftm potato fields than in fields of non-transgenic potato counterparts, and more abundant than in those treated with conventional chemical insecticides.

Dietary toxicity studies have been 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 effect was observed, except for slightly higher mortality and reduced honeydew production of green peach aphids. Green peach aphids are major vectors of potato viruses in Canada, specifically of the potato leaf roll virus, and are chemically controlled in standard potato production systems. The effect of NewLeaftm potatoes on these aphids is therefore negligible in terms of environmental impact.

Numerous oral acute and short term studies were undertaken with albino mice, Sprague- Dawley rats, northern bobwhite and bobwhite quails. The animals were fed NewLeaftm potatoes or protein extracts. Treatment related effects were not observed. These observations were expected, as the novel proteins are rapidly inactivated in simulated mammalian stomach fluids by enzymatic degradation and pH-mediated proteolysis. The proteins expressed in NewLeaftm Atlantic potatoes were shown to be equivalent to the original microbial proteins produced by the common soil B.t.t. bacteria.

Based on the above, CFIA has determined that the unconfined release of these NewLeaftm Atlantic lines, when compared with currently commercialized potato varieties, will not result in altered impacts on interacting organisms, including humans, with the exception of CPB and potato flea beetles.

5. Potential Impact on Biodiversity

NewLeaftm Atlantic lines have no novel phenotypic characteristics which would extend their use beyond the current geographic range of potato production in Canada. Since potato does not outcross to wild relatives in Canada, there will be no transfer of novel traits to unmanaged environments.

The use of NewLeaftm Atlantic potato plants could reduce the need for some foliar insecticidal sprays, resulting in a reduction of chemicals released into the environment, an increase of non-target insect populations, and an increase in potential for biological control of harmful insect pests.

CFIA has therefore concluded that the potential impact on biodiversity of these NewLeaftm Atlantic potato lines, if any, would be positive.

6. Potential for Development of CPB Resistance to the PNT's

The potential for CPB to develop resistance to conventional chemical insecticides is well documented, and many of the currently registered chemical foliar sprays no longer control CPB. Foliar insecticides based on the B.t.t. proteins present in NewLeaftm Atlantic potatoes are registered in Canada for use on both potatoes and tomatoes. To date, resistance of CPB to B.t.t. has not been observed under field conditions. Resistance may develop as a result of increased use of these B.t.t. foliar sprays; resistance to the B.t.t. protein could also develop following continued exposure to the NewLeaftm potatoes.

The development of such a resistance would result in the loss of these valuable B.t.t. tools for the control of CPB infestations in both potatoes and tomatoes.

NewLeaftm Atlantic potatoes steadily produce high levels of readily accessible B.t.t. proteins, resulting in high mortality in CPB feeding on NewLeaftm. Target insects will thus be exposed to significantly higher levels of B.t.t. than through the current foliar spray treatments, leading to high selection pressures for resistant CPB individuals. A major component of the resistance management strategy linked to the use of these NewLeaftm Atlantic potatoes is the presence of non-selecting refugia (regular potatoes) in close proximity, where susceptible insect populations are maintained. Should resistant insects occur, they would then be able to mate with susceptible insects to produce heterozygotes, which are expected to be susceptible to the B.t. ð-endotoxins produced by the NewLeaftm potatoes. Even though the majority of the scientific community agrees that this approach sounds effective in theory, it is very difficult at this point to predict the extent and rapidity of resistance development without field validation of the proposed strategy. These potato plants should therefore be responsibly managed and CPB populations monitored for development of resistant individuals in a regular and consistent manner.

Consideration must be given to the possibility that CPB populations developing resistance to NewLeaftm potatoes could also be cross-resistant to other B.t. ð-endotoxins, resulting in the loss of other B.t. protein types that may be used for the control of CPB infestations. To date however, no B.t. proteins other than B.t.t. are registered for use against CPB in Canada.

The development of resistance to the B.t.t. proteins by non-target insect pests, that may then cause further problems in other crops, is another consideration. Potato flea beetles (Coleoptera: Chrysomelidae, Epitrix cucumeris Harris) can cause significant damage to potatoes, especially in the Maritimes (10-25% yield reduction), and can also visit cucumbers, eggplants, peppers and tomatoes. Tuber flea beetles (Coleoptera: Chrysomelidae, Epitrix tuberis Gentner) feed on potatoes and tomatoes. It is a very serious pest west of the Rockies and is also found in Alberta. Potato flea beetles (E. cucumeris) have been shown to be affected by the NewLeaftm potatoes, but they can survive. This species and others in this genus may develop resistance to the B.t.t. insecticidal proteins. Presently, B.t.t. foliar sprays are not registered for control of these beetles in Canada, due to reduced efficacy, so even should resistance occur, control of these insects would not be compromised. CFIA has therefore concluded that development of resistance in non-target insect pests is unlikely to have an impact on the conventional control of these pests.

CFIA believes that sound management practices can reduce and delay the development of resistant CPB populations. CFIA understands that NatureMark Potatoes has developed and will implement a pest resistance management plan that includes the following key components:

• The early detection of resistant CPB populations is extremely important. Close monitoring for the presence of such populations, in NewLeaftm potato fields and surrounding areas, is therefore warranted. Monitoring includes the development of appropriate detection tools such as visual field observations and laboratory bioassays, reporting schedules, education of growers, and enforcement procedures.
• Education tools for growers and field managers will be developed, with descriptions such as: production practices; detection protocols for resistant CPB individuals; monitoring procedures and timetables; and strategies to be followed in case of detection of resistant insects.
• Integrated Pest Management practices will be promoted, such as prediction of infestation problems from previous years, crop rotation, and use of trap trenches.
• Detection of confirmed resistant CPB populations will immediately be reported to CFIA and a procedure for control of resistant individuals must be available for immediate action.

The strategy for resistance management of CPB when using plants that continually produce high concentrations of a B.t.t. ð-endotoxin and refugia has not been previously tested in the field on a large scale. Continued research in this area using sound science will be conducted.

The plans, information and data from the above are available to CFIA.  CFIA has also strongly encouraged NatureMark Potatoes to develop novel CPB control systems with different modes of action that would offer additional or alternative management practices to growers.

If at any time, NatureMark Potatoes becomes aware of any new information regarding risk to the environment, including risk to agriculture such as development of CPB resistance, or risk to animal or human health, that could result from release of these materials in Canada, or elsewhere, NatureMark Potatoes will immediately provide such information to CFIA. On the basis of such new information, CFIA will re-evaluate the potential impact of the proposed release, and will re-evaluate its decision.

V. Nutritional Assessment Criteria as Livestock Feed

1. Anti-Nutritional Factors

Glycoalkaloid content in the transformed lines varied over the four sites tested but was similar to control levels in all but one case. At one site the glycoalkaloid content was significantly higher in one of the transformed lines compared to control, but within the accepted range for this natural toxicant in presently registered potato varieties. Data concerning glycoalkaloid content is reviewed by the National Potato Variety Registration Recommending Committee for all potato varieties recommended for registration.

2. Nutritional Composition of the PNT's

Comparisons of protein, fat, fibre and ash from the PNT lines and the Atlantic parent line were made. Mean fat content of the transformed lines was slightly lower when compared to the Atlantic control as a result of variation at some of the sampling locations which affected the overall mean. Fat is a minor component of potatoes and all values for total fat content were within the range expected for potatoes. Protein, fibre and ash content were similar when the PNT's and controls were compared. There were individual differences between the PNT and the control for these nutrients but there was no consistent pattern of variation.

Protein, fat, fibre and ash concentration were within the published range for potatoes in all the transformed lines. The observed variation in nutritional composition were judged to arise from normal variability rather than as a result of the inserted novel traits. CFIA has determined that the NewLeaftm Atlantic potato lines are substantially equivalent to their unmodified counterparts.

VI. Regulatory Decision

Based on the review of data and information submitted by NatureMark Potatoes, and through thorough comparisons of the NewLeaftm Atlantic potato lines with unmodified potato counterparts, the Plant Biosafety Office of the Plant Health and Production Division, CFIA, has concluded that the novel genes and their corresponding traits do not confer to the NewLeaftm Atlantic lines any characteristic that would result in intended or unintended environmental effects following unconfined release.

Based on the review of submitted data, the Feed Section of the Plant Health and Production Division has concluded that the novel genes expressed by the NewLeaftm Atlantic potato lines do not raise safety or nutritional concerns as livestock feed. Potatoes, including potato process residue, are currently listed in Schedule IV of the Feeds Regulations an are therefore approved for use in livestock feeds in Canada. As the NewLeaftm Atlantic potato lines have been assessed and found to be substantially equivalent to traditional potato varieties with respect to safety, NewLeaftm Atlantic potato lines and their byproducts are approved for use as livestock feed ingredients in Canada.

Unconfined release into the environment, including feed use of the NewLeaftm Atlantic potato lines ATBT04-6, ATBT04-27, ATBT04-30, ATBT04-31, ATBT04-36 is therefore authorized. Also, any S. tuberosum lines derived from them, or resulting from the same transformation events, may be released, provided that: no inter-specific crosses are performed; the intended use is similar; it is known following thorough characterization that these plants do not display any additional novel traits; and the understood pest resistance management plan summarized in this document is applied.

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: