Database Product Description
- Host Organism
- Solanum tuberosum (Potato)
- Trade Name
- Atlantic and Superior NewLeaf®
- Resistance to Colorado potato beetle (Leptinotarsa decemlineata, Say).
- Trait Introduction
- Agrobacterium tumefaciens-mediated plant transformation.
- Proposed Use
Production for human consumption and livestock feed.
- Product Developer
- Monsanto Company
Summary of Regulatory Approvals
Summary of Introduced Genetic Elements Expand
Characteristics of Solanum tuberosum (Potato) Expand
Donor Organism Characteristics Expand
Modification Method Expand
Characteristics of the Modification Expand
Environmental Safety Considerations Expand
Food and/or Feed Safety Considerations Expand
Potato (Solanum tuberosum L.) is grown commercially in over 150 countries with a combined harvest of over 315 million metric tonnes in 2006. The major producers of potatoes are China, Russia, India, the United States, Ukraine, Poland and Germany. Potatoes are the fourth most important food crop in the world, providing more edible food than the combined world output of fish and meat. They are grown for the fresh and processed food industries, especially the frozen food sector. In North America, potato tubers are used primarily for French fries, chips, and dehydrated flakes. Other food uses of the crop include consumption of fresh tubers, and in the production of flour, starch and alcohol.
Colorado potato beetle (CPB; Leptinotarsa decemlineata [Say]) is the most destructive insect pest of potatoes in North America. The adult and all larval stages feed primarily on foliage and occasionally on stems. When the population of beetles is high, plants can be completely defoliated. Extensive feeding at any time during the growing season can reduce yield, as a reduction in leaf surface area decreases the plant’s ability to produce and store nutrients, which affects tuber size and number.
Commercial production of potatoes is nearly impossible without using insecticides to control CPB. Thirty-four percent of total insecticide use on potatoes is for control of CPB, more than used on any other insect potato pest. There are several insecticide classes that are available for Colorado potato beetle control including organophosphates, carbamates, pyrethroids, chlorinated hydrocarbons, insect growth regulators, chloronicotinyl, spinosads and abamectins. Colorado potato beetle has shown a tremendous ability to develop resistance to insecticides, including the arsenicals, organochlorines, carbamates, organophosphates, and pyrethroids. Cross-resistance to organophosphates and carbamates, and multiple resistance to organophosphates, carbamates, and pyrethroids has also been reported.
The transgenic cultivars of ‘Atlantic’ (ATBT04-6, ATBT04-27, ATBT04-30, ATBT04-31, ATBT04-36) and ‘Superior’ (SPBT02-5, SPBT02-7) NewLeaf® potatoes were genetically engineered to be resistant to attack by CPB. These lines were developed by introducing the cry3A gene, isolated from the common soil bacterium Bacillus thuringiensis subspecies tenebrionis (Btt), into the potato genome by Agrobacterium-mediated transformation.
The Cry3A protein expressed in these transgenic potato cultivars is identical to that found in nature and in commercial Bt spray formulations. Cry proteins, of which Cry3A is only one, act by selectively binding to specific sites localized on the lining of the midgut of susceptible insect species. Following binding, pores are formed that disrupt midgut ion flow causing gut paralysis and eventual death due to bacterial sepsis. Cry3A is insecticidal only when eaten by the larvae of coleopteran insects such as Colorado potato beetle and its specificity of action is directly attributable to the presence of specific binding sites in the target insects. There are no binding sites for delta-endotoxins of B. thuringiensis on the surface of mammalian intestinal cells, therefore, livestock animals and humans are not susceptible to these proteins.
Over several years of field-testing, these transgenic potatoes have been compared to non-transgenic ‘Atlantic’ and ‘Superior’ cultivars 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, Epitrix cucumeris Harris) were affected to some extent. Overall the field data reports and data on agronomic traits showed that the CPB-resistant potato lines did not otherwise differ from their non-transgenic counterparts.
Dietary toxicity studies were performed using the Cry3A protein on four beneficial insects (honeybee, ladybird beetle, green lacewing and parasitic wasp), and eight non-target insect species (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, which as vectors of damaging potato viruses, are normally controlled in potato fields by chemical means. The transgenic Atlantic and Superior potato lines were not expected to impact on threatened or endangered species.
Generally, varieties of S. tuberosum are capable of cross-hybridization with each other, but genetic exchange with other Solanum species is usually unsuccessful. In Canada there are no tuber producing wild relatives of Solanum. In the United States, tuber-bearing Solanum species include S. jamesii, S. fendleri, and S. pinnatisectum, however, the possibility of cultivated potato crossing with these species is remote because of geographical isolation and other biological barriers to natural hybridization. No natural hybrids have been observed between these species and cultivated S. tuberosum.
Gene transfer from the transgenic Atlantic and Superior potato lines to other potato cultivars is unlikely. Since the reproductive characteristics of the CPB-resistant potato lines were unchanged by the genetic modification, they should be no different than the parent cultivars. Gene exchange between and CPB-resistant potatoes and other Solanum species is very unlikely and is limited to cross-pollination with other potatoes.
Regulatory authorities in Canada and the United States have mandatory requirements for developers of Bt potatoes to implement specific Insect Resistant Management (IRM) Programs. The potential exists for Bt-resistant CPB populations to develop as acreages planted with transgenic CPB-resistant potatoes expand. Hence, these IRM programs are designed to reduce this potential and prolong the effectiveness of plant-expressed Bt toxins, and the microbial Bt spray formulations that contain these same toxins.
Potatoes are considered to be a staple food in North America, constituting up to 37% of the total average vegetable intake. The genetic modification present in the ATBT04-6, ATBT04-27, ATBT04-30, ATBT04-31, ATBT04-36, SPBT02-5 and SPBT02-7 transgenic lines will not result in any change in the consumption pattern for potatoes. Due to their protection from CPB damage, the NewLeaf® Atlantic and Superior cultivars are expected to replace some existing commercial potato cultivars in all potato product applications. Hence, they will provide an alternate or additional choice to consumers and food manufacturers.
The major components of CPB-resistant potato lines were analyzed for nutritional constituents, proximate composition (protein, fat, ash, total dietary fibre, carbohydrate, and calories), internal quality characteristics (hollow heart and brown center, internal brown spots, vascular discoloration, and blackspot bruise), and French fry quality characteristics and compared with those of non-transgenic ‘Atlantic’ and ‘Superior’ tubers. The analysis of nutrients from each of these transgenic potato lines and from non-transgenic potatoes did not reveal any significant differences in levels of crude protein, ash, or starch. Similarly, the levels of micronutrients and trace elements, including thiamine, niacin, riboflavin, vitamin C, calcium, iron and zinc, were comparable to those of unmodified counterpart potatoes. It was concluded that the consumption of products from CPB-resistant potatoes would have no significant impact on the nutritional quality of the food supply.
The glycoalkaloids, solanine and chaconine, are naturally occurring toxicants found in potato tubers, particularly green tubers that have been exposed to sunlight. Analyses of total glycoalkaloid levels in each of the transgenic lines demonstrated that in each case the levels were within the standards previously established for potatoes.
The potential for allergenicity and toxicity of the Cry3A protein was assessed based upon the physiochemical properties of known food allergens, such as stability to acid and/or proteolytic digestion, heat stability, and glycosylation. Cry3A did not demonstrate any characteristics normally associated with food allergens. Unlike known protein allergens, which are normally resistant to digestion, Cry3A was rapidly inactivated and degraded when subjected to typical mammalian acidic stomach conditions. The amino acid sequence of the Cry3A protein was not found to be homologous with those of known protein toxins or allergens. Additionally, the Cry3A protein has a history of safe use as demonstrated by its application in microbial Bt spray formulations in agriculture and forestry for more than 30 years with no evidence of adverse effects. These facts were sufficient to provide with reasonable certainty that the Cry3A protein, and thus the transgenic Atlantic and Superior potato lines, possessed little or no potential for allergenicity or toxicity.
Links to Further Information Expand
This record was last modified on Friday, March 26, 2010