Database Product Description
- Host Organism
- Beta vulgaris (Sugar Beet)
Herbicide tolerant, glyphosate.
- Trait Introduction
- Agrobacterium tumefaciens-mediated plant transformation.
- Proposed Use
Production for human consumption.
- Product Developer
- Monsanto Company
Summary of Regulatory Approvals
Summary of Introduced Genetic Elements Expand
Characteristics of Beta vulgaris (Sugar Beet) Expand
Donor Organism Characteristics Expand
Modification Method Expand
Characteristics of the Modification Expand
Environmental Safety Considerations Expand
Food and/or Feed Safety Considerations Expand
Sugar beet (Beta vulgaris L. ssp. vulgaris var. altissima) had a global harvest of 256 million metric tonnes in 2006. The major producers of sugar beet in 2004 were France, the United States, Germany, Russian Federation, Turkey, Ukraine and Poland. Sugar beet is a botanical variety of B. vulgaris ssp. vulgaris, as are other comestible and fodder beets, and is a member of the goosefoot (Chenopodiaceae) family. It is an important source of sugar (sucrose), accounting for approximately 40 percent of global production.
Sucrose is present in limited quantities in many plants, including various palms and the sugar maple, but sugar beet and sugarcane are the only commercially important sources. More than half of the world sugar supply is obtained from sugarcane, which is grown in tropical and subtropical climates. The rest is supplied by the sugar beet, which is grown in temperate countries. Sugar is manufactured from the roots of the sugar beet; the leaves and tops are removed after harvesting and used as livestock feed. The roots are cut into cossettes, or chips, from which the juice is extracted. The juice is processed to yield sugar and beet molasses, and the remaining pulp is used for domestic animal feed. Beet molasses is also fed to livestock; table molasses is not made from sugar beets because of difficulties in purification. The sugar (sucrose) that is produced from the sugar beet is identical to that derived from sugarcane. It is widely used as a sweetener for foods, in preserves, and in the manufacture of candies, baked goods, and soft and alcoholic beverages. Sugar is also used as the raw material for fermentation products such as ethyl alcohol, butyl alcohol, glycerin, citric acid, and levulinic acid. Sugar is an ingredient in some transparent soaps, and it can be converted to esters and ethers, some of which yield tough, insoluble, and infusible resins.
Effective weed management is critical to sugar beet production. Weeds cause significant losses in sugar beet yield and crop quality, and also cause harvesting problems. The low growth habit of the sugar beet plant renders it more susceptible to competition from weeds compared to other crops, such as corn or soybean. Many weed species grow taller than sugar beet and thus aggressively compete for light, water and nutrients. The economic threshold for weed control in sugar beet production is therefore quite low, given the high value of the crop, and the significant losses caused by the presence of weeds. Weeds control strategies include the use of herbicides alone, and herbicides in combination with hand weeding. Sugar beet herbicides can be applied prior to crop emergence (e.g., triallate, EPTC, ethofumesate), and post-emergence (e.g., ethofumesate, triflusulfuron, desmedipham, phenimedipham, sethoxydim).
H7-1 sugar beet was developed to allow for the use of glyphosate, the active ingredient in the herbicide Roundup®, as a weed control option. This genetically engineered sugar beet line contains a form of the plant enzyme 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) that allows it to survive the otherwise lethal application of glyphosate. The EPSPS gene that was introduced into H7-1 was isolated from the common soil bacterium Agrobacterium tumefaciens, strain CP4 and the form of EPSPS enzyme produced by this gene is tolerant to glyphosate.
The EPSPS enzyme is part of the shikimate pathway, an important biochemical pathway in plants involved in the production of aromatic amino acids and other aromatic compounds. When conventional plants are treated with glyphosate, the plants cannot produce the aromatic amino acids needed for growth and survival. EPSPS is present in all plants, bacteria, and fungi. It is not present in animals, which do not synthesize their own aromatic amino acids. Because the aromatic amino acid biosynthetic pathway is not present in mammals, birds or aquatic life forms, glyphosate has little if any toxicity for these organisms. The EPSPS enzyme is naturally present in foods derived from plant and microbial sources.
The sugar beet line H7-1 was field tested in the United States from 1998 to 2002, and in Europe (France and Germany) in 1998-99. H7-1 was evaluated extensively and no differences were found in agronomic performance, disease and insect resistance, leaf morphology, seed germination and dormancy, seedling and plant vigour, bolting, flowering onset, and seed harvest date when compared to conventional sugar beet cultivars. Field observations demonstrated that the cultivation of H7-1 did not negatively affect beneficial and non-target organisms, compared to that of conventional sugar beet.
Sugar beet is an outcrossing species, and is mainly wind pollinated. It is a biennial, developing a rosette of leaves and a large taproot in the first year, and bolting (i.e., forming an inflorescence bearing stem) in the second year. Bolting is induced only after the plant has undergone vernalisation at the end of the first season. Certain environmental conditions, such as low temperatures and longer daylength, may induce bolting in the first year. Large amounts of pollen are produced during the reproductive phase; this pollen can be wind-borne over long distances. Sugar beet is also very sensitive to frost, and is a poor competitor with other plants.
The genus Beta is comprised of four sections: i) Beta, to which sugar beet belongs; ii) Corollinae; iii) Nanae; and iv) Procumbentes. All species within the Beta section (e.g., B. vulgaris ssp. maritima, B. macrocarpa) are cross-compatible and produce fertile progeny. Hybrids between sugar beet and members of the other three sections do not occur naturally, and cross-breeding with other members of the Chenopodiaceae is unlikely. As with conventional sugar beet cultivars, H7-1 plants are harvested prior to the initiation of the bolting phase. Since sugar beets are usually not allowed to bolt, except in fields or plots grown for seed production, there is little opportunity for uncontrolled pollen flow. Sugar beets grown for seed production are also isolated from other sugar beet fields to minimize pollen flow. This is usually achieved by the use of isolation distances enforced by seed certification agencies.
The development of glyphosate-tolerant hybrids is possible due to the ability of sugar beet to outcross with related plants. However, the glyphosate tolerance trait is not expected to provide a competitive advantage to hybrid plants unless grown in managed environment routinely subjected to glyphosate applications. In the event that a glyphosate-tolerant hybrid survived, it could be controlled using mechanical and/or other available chemical means. H7-1 is considered unlikely to increase the weediness potential of any other cultivated plant or native wild species with which it may interbreed. H7-1 also does not possess growth and reproductive characteristics that would render it weedier than conventional sugar beet.
Sugar beet intended for human consumption is generally converted directly to refined white sugar through extensive purification processes. The levels of CP4 EPSPS protein introduced into H7-1 sugar beet were not measured in refined sugar. CP4 EPSPS was expressed at very low levels in the roots, and since refined sugar does not contain detectable levels of protein, there would be virtually no human exposure to CP4 EPSPS. Consequently, there is no anticipated human exposure to this protein as a result of consumption of refined sugar derived from H7-1 sugar beet.
Detailed analyses were carried out to establish the nutritional value of H7-1 sugar beet. The transgenic H7-1 line was compared with non-transgenic sugar beets in an analysis of numerous compositional components, including crude ash, crude fibre, crude protein, carbohydrate and dry matter in both tops and roots (processed). Additional quality components were measured in processed roots including, invert sugar content, polarization (% sucrose), sodium, potassium and alpha-amino nitrogen. No biologically meaningful differences in any compositional or quality parameters relevant to food were identified between non-transgenic, control sugar beet and sugar beet H7-1. It was concluded that glyphosate-tolerant sugar beet H7-1 is equivalent to other commercially available sugar beet varieties with respect to composition and nutritional quality.
The presence of naturally occurring toxins and allergens in glyphosate-tolerant sugar beet line H7-1 was investigated. Saponins are the only known toxicants found in sugar beet and are actively eliminated in sugar processing. These are also considered antinutrients since they impart a bitter taste to animal feed and reduce intake. Levels of saponin in H7-1 did not differ significantly from those of the control lines, and were within the range observed for conventional sugar beet cultivars.
The potential toxicity and allergenicity of the CP4 EPSPS protein was assessed. No significant homologies between the amino acid sequence of CP4 EPSPS and those of known toxins or allergens were detected. The protein did not display the characteristics usually associated with allergenic substances, and was readily degraded under conditions simulating the mammalian digestive environment. Acute oral gavage studies, in which mice were fed high doses of the CP4 EPSPS protein, did not reveal any toxic effects and provided further support to the conclusion that this protein, and thus the transgenic H7-1 sugar beet line, possessed little or no potential for toxicity.
Links to Further Information Expand
This record was last modified on Friday, August 11, 2017