GM Crop Database

Database Product Description

Host Organism
Zea mays (Maize)
Imidazolinone herbicide tolerance.
Trait Introduction
Selection of somaclonal variants from embryo cultures.
Proposed Use

Production for human consumption and livestock feed.

Product Developer
Pioneer Hi-Bred International Inc.

Summary of Regulatory Approvals

Country Food Feed Environment Notes
Canada 1994 1996 1996

Summary of Introduced Genetic Elements Expand

Code Name Type Promoter, other Terminator Copies Form
als acetolactate synthase MUT Imidazolinone selection of somatic embryos

Characteristics of Zea mays (Maize) Expand

Center of Origin Reproduction Toxins Allergenicity

Mesoamerican region, now Mexico and Central America

Cross-pollination via wind-borne pollen is limited, pollen viability is about 30 minutes. Hybridization reported with teosinte species and rarely with members of the genus Tripsacum.

No endogenous toxins or significant levels of antinutritional factors.

Although some reported cases of maize allergy, protein(s) responsible have not been identified.

Abstract Collapse

Maize (Zea mays L.), or corn, is grown primarily for its kernel, which is largely refined into products used in a wide range of food, medical, and industrial goods.

Only a small amount of whole maize kernel is consumed by humans. Maize oil is extracted from the germ of the maize kernel and maize is also a raw material in the manufacture of starch. A complex refining process converts the majority of this starch into sweeteners, syrups and fermentation products, including ethanol. Refined maize products, sweeteners, starch, and oil are abundant in processed foods such as breakfast cereals, dairy goods, and chewing gum.
In the United States and Canada maize is typically used as animal feed, with roughly 70% of the crop fed to livestock, although an increasing amount is being used for ethanol production. 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, pharmaceuticals and car parts.

The maize line 3751IR was developed to express tolerance to imidazolinone herbicides, a class of herbicides which target and bind to the acetolactate synthase (ALS) enzyme in plants. ALS catalyzes the first reaction in the biosynthesis of branched-chain amino acids. Imidazolinone inhibits the production of these essential amino acids (valine, leucine and isoleucine), resulting in a decrease in protein synthesis and the eventual death of the plant. ALS is also active in the glycolytic pathway of plant metabolism, by which sugars are broken down to produce acids and release energy.

Imidazolinones applied at rates recommended for effective weed control are toxic to currently cultivated maize varieties. Imidazolinone tolerance in 3751IR maize results from a mutation in the ALS enzyme. The mutant form of ALS in 3751IR prevents the binding of imidazolinone herbicides to the enzyme, allowing the 3751IR maize plants to survive application of the herbicide. The mutant form of ALS is not otherwise altered, and its ability to regulate the levels of the branched-chain amino acids via feedback inhibition is equivalent to that of unaltered ALS.

The maize line 3751IR was developed from a mutant line (XA17) selected from somatic (non-reproductive) maize embryos grown on imidazolinone-enriched media under conditions designed to induce mutation. The imidazolinone-enriched media selects for those mutants expressing tolerance to imidazolinone. The chosen mutant cell line XA17 was regenerated to a whole plant and crossed to the inbred maize line B73. A further series of crosses involving this XA17/B73 line resulted in the production of the hybrid 3751IR.

As the development of 3751IR did not employ recombinant DNA technologies, this product was not subject to regulation in any jurisdiction except Canada, where it was regulated as a plant with novel trait under the Seeds Act, a novel feed under the Feeds Act, and as a novel food under the Food and Drug Regulations. Specific environmental, livestock feed, and food safety assessment of this product was only required for Canada.

Links to Further Information Expand

This record was last modified on Tuesday, February 24, 2015