Database Product Description
- Host Organism
- Solanum tuberosum (Potato)
- Trade Name
- NewLeaf® Y
- Resistance to Colorado potato beetle (Leptinotarsa decemlineata, Say); resistance to potato virus Y (PVY).
- 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 CPB 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.
Potato virus Y (PVY), the type member of the potyvirus group, is known to infect over 342 plant species in 69 genera and 27 families. PVY naturally infects solanaceous plants (e.g., potato, pepper, tomato and tobacco) worldwide and is particularly prevalent in warmer climates. This rod-shaped RNA virus can cause serious damage to potato production, reducing yields from 10% to 80%, and is reported as one of the major causes for the rejection of seed potatoes in virus-free certification programs. PVY has been characterized into many strains but generally falls into three main groups, PVY-O (ordinary), PVY-N (necrotic) and PVY-C (stipple streak). Strains are characterized on the basis of the plant symptoms produced in a set of selected potato and tobacco cultivars. Disease severity depends on PVY strain, host tolerance, time of infection and environmental factors. In potato, PVY is transmitted to the new crop via seed tubers and in a non-persistent manner by the green peach aphid (Myzus persicae) and other aphid vectors. Infection occurs when aphids acquire the virus from an infected plant and carry the virus to another, introducing it into the host as they feed. Primary symptoms caused by PVY may be mild or hardly detectable, which causes problems particularly in seed potato production.
Traditionally, control of PVY has been achieved using a variety of approaches, including: the use of certified virus-free tubers for planting; the elimination of potato volunteers and weeds; destroying cull piles (which can serve as reservoirs of infected plant material); and the use of resistant cultivars.
The transgenic Shepody NewLeaf® Y potato lines, SEMT15-02 and SEMT15-15, and Russet Burbank NewLeaf® Y RBMT15-101, were produced using recombinant DNA techniques and contain two novel genes, whose individual expression results in resistance to attack by CPB and resistance to infection by PVY-O. Resistance to attack by CPB was accomplished by introducing the cry3A gene from Bacillus thuringiensis subsp. tenebrionis, which encodes an insecticidal crystalline Cry3A delta-endotoxin protein. The insecticidal activity of Cry3A protein is due to its selective binding to specific sites localized on the brush border midgut epithelium of susceptible insect species. Following binding, cation-specific pores are formed that disrupt midgut ion flow and thereby cause gut paralysis, ultimately leading to bacterial sepsis and death. Delta-endotoxins, such as the Cry3A protein expressed in CPB resistant potato lines, exhibit highly selective insecticidal activity against a narrow range of coleopteran insects such as CPB, elm leaf beetle and yellow mealworm. Their specificity of action is directly attributable to the presence of specific receptors in the target insects. There are no receptors for delta-endotoxins of B. thuringiensis on the surface of mammalian intestinal cells, therefore, livestock animals and humans are not susceptible to these proteins.
Pathogen-derived resistance to PVY was conferred by introducing the coat protein (CP) gene from PVY-O. The coat protein forms a protective coat around the RNA genome of the virus and comprises 95% by mass of the virus particle. Although the exact mechanism is not fully understood, these transgenic potato lines exhibit resistance to infection and subsequent disease caused by PVY through a process that is related to viral cross-protection.
RBMT15-101, SEMT15-02 and SEMT15-15 potato lines were tested in field trials in both the United States and Canada, and data collected from the trials demonstrated that these potato lines grew normally and exhibited the characteristics normally associated with Russet Burbank or Shepody cultivars, except for resistance to attack by CPB and infection with PVY. Transgenic NewLeaf® Y potato lines did not pose a plant pest risk, negatively affect beneficial or nontarget organisms, or exhibit enhanced weediness potential.
Generally, varieties of S. tuberosum are capable of crossbreeding with each other. However, transgenic NewLeaf® Y potato line RBMT15-101 was derived from the male sterile ‘Russet Burbank’ potato, which does not produce pollen. As a result, it is not possible for RBMT15-101 to cross-pollinate with other potato varieties, or with any related wild relatives.
The reproductive characteristics of SEMT15-02 and SEMT15-15 were unchanged by the genetic modification and the frequency of cross-pollination should be no different than for conventional potato varieties. The chances for successful hybridization between transformed Shepody NewLeaf® Y potato lines and most wild relatives are unlikely as potatoes (Solanum tuberosum) only form natural hybrids with Solanum species that bear tubers. 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.
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.
The food and livestock feed safety of NewLeaf® Y potato lines was established based on several standard criteria, including analyses of key nutrients, total solids, sugars, vitamin C, soluble protein and proximates (e.g., total protein, moisture, fat, ash, crude fibre, carbohydrates and calorie content). These analyses of macro- and micronutrients revealed only small differences between transgenic and non-transgenic control lines and in each case the level was within the normal range of variation reported for commercial potatoes.
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 (TGA) levels in each of the transgenic lines demonstrated that in each case the levels were within the standard levels previously established for potatoes.
Neither of the Cry3A protein nor PVY CP shares amino acid sequence homology with any known protein toxins. Previous studies on the acute oral toxicity of Cry3A protein have established that this protein does not result in any adverse effects when fed to laboratory mice at doses up to 5220 mg/kg body weight. Toxicity testing was not required for the PVY CP because of the long history of exposure of human beings to this protein through the consumption of PVY-infected potatoes.
The Cry3A protein and PVY CP do not possess characteristics typical of known protein allergens. There were no regions of homology when the amino acid sequences of these introduced proteins were compared to the amino acid sequences of known protein allergens, and unlike known protein allergens, the Cry3A protein was rapidly degraded by simulated gastric or intestinal fluids. It was determined that these two proteins were highly unlikely to be allergenic.
Links to Further Information Expand
This record was last modified on Wednesday, September 7, 2016