Database Product Description
- Host Organism
- Zea mays L. (Maize)
Glyphosate herbicide tolerance and resistance to corn root worm (Coleoptera, Diabrotica sp.).
- Trait Introduction
- Agrobacterium tumefaciens-mediated plant transformation.
- Proposed Use
Production of Z. mays for human consumption (wet mill or dry mill or seed oil), and meal and silage for livestock feed. These materials will not be grown outside the normal production area for corn.
- Product Developer
- Monsanto Company
Summary of Regulatory Approvals
Summary of Introduced Genetic Elements Expand
Characteristics of Zea mays L. (Maize) Expand
Donor Organism Characteristics Expand
Modification Method Expand
Characteristics of the Modification Expand
Environmental Safety Considerations Expand
Food and/or Feed Safety Considerations Expand
Maize, or corn (Zea mays L.) is grown commercially in over 100 countries with a combined harvest of nearly 700 million metric tonnes in 2006. The top five producers of maize in 2005 were the United States, China, Brazil, Argentina, and Mexico, accounting for 70% of world production. Maize is grown primarily for its kernel (grain), the majority of which is used for animal feed, but with significant amounts refined into products used in a wide range of food, medical, and industrial goods.
Maize is a raw material for the manufacture of starch, the majority of which is converted by a complex refining process into sweeteners, syrups, and fermentation products, including ethanol. Maize oil is extracted from the germ of the maize kernel. Only a small proportion of the whole kernel is consumed by humans (e.g., corn meal, grits, oil), while refined maize products such as sweeteners, starch, and oil are abundant in processed foods (e.g., breakfast cereals, dairy goods, chewing gum). Maize is also processed into masa, which is used for tortillas, tacos and corn chips.
In the United States maize is typically used as animal feed, with roughly 70% of the crop fed to livestock, however a growing amount is now being used for the production of ethanol. The entire maize plant, the kernels, and several refined products such as glutens and steep liquor, are used in animal feeds. Silage made from the whole maize plant makes up 10-12% of the annual corn acreage, and is a major ruminant feedstuff. Livestock that feed on maize include cattle, pigs, poultry, sheep, goats, fish and companion animals.
Industrial uses for maize products include recycled paper, paints, cosmetics, car parts. Refined maize products are also used in bioproducts such as antibiotics.
Corn rootworm (Diabrotica spp.) is considered one of the most damaging insects pests of maize. The species of corn rootworm most prevalent in the United States are the northern corn rootworm (Diabrotica barberi) and the western corn rootworm (D. virgifera). The larvae of these beetles (coleopterans) feed on the corn roots. Feeding damage to the roots impedes the absorption of water and nutrients. Corn rootworms also feed on the brace roots and cause plant lodging. Adults feed on the silks thus interfering with pollination and seed set. Crop rotation is a recommended practice to reduce the population of these insects; thus, corn should not follow corn in a rotation. The protection offered by insecticides is limited: these will protect the crop from rootworm damage, but will only reduce a small percentage of the beetles from emerging.
Weeds are also a major production problem in maize cultivation. Typically, weeds are managed using a combination of cultural (e.g., seed bed preparation, clean seed, variety selection) and chemical controls. Depending on the production area and the prevalent weed species, herbicides may be incorporated into the soil before planting (pre-plant), applied after planting but before emergence (pre-emergence), or applied after the maize plants emerge (post-emergence). Ideally, for maize production, weeds should be controlled for the full season. However, the most critical period for weed control is usually about six to eight weeks after crop emergence, during the 4th to 10th leaf stages. This critical period in the life cycle of maize must be kept weed free in order to prevent yield loss.
The transgenic maize line MON 88017 was genetically engineered to resist the western corn rootworm (Diabrotica virgifera) and northern corn rootworm (D. barberi) by producing an insecticidal protein, and to express tolerance to the herbicide glyphosate. Two novel genes, a variant of the cry 3Bb1 gene and cp4 epsps, were introduced into the maize line LH198 using Agrobacterium -mediated transformation.
The cry3Bb1gene, isolated from the soil bacterium Bacillus thuringiensis (Bt) subspecies kumamotoensis strain EG4691, produces the insect control protein (delta-endotoxin) Cry3Bb1. Cry proteins, of which Cry3Bb1 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. Cry3Bb1 is lethal only when eaten by the larvae of coleopteran insects (i.e. , beetles), 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 the delta-endotoxins of B. thuringiensis on the surface of mammalian intestinal cells, therefore, livestock animals and humans are not susceptible to these proteins.
The cp4 epsps gene, isolated from Agrobacterium tumefaciens strain CP4, codes for a form of the enzyme 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) which 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 food and livestock feed safety of MON 88017 maize grain and forage was established based on several standard criteria. As part of the safety assessment, the nutritional composition of MON 88017 grain was found to be equivalent to conventional maize as shown by the analyses of key nutrients including proximates (i.e. , moisture, crude protein, crude fat, ash and carbohydrates), acid detergent fibre, neutral detergent fibre, total dietary fibre, amino acid composition, fatty acid profiles, minerals (e.g. , calcium, phosphorus, magnesium), and vitamins (i.e., folic acid, niacin, vitamin E), as well as antinutrient compounds. Similar compositional analyses were conducted on MON88017 forage harvested at the late dough to early dent stages.
Links to Further Information Expand
This record was last modified on Thursday, February 26, 2015