GM Crop Database

Database Product Description

IMINTA-1, IMINTA-4
Host Organism
Oryza sativa (Rice)
Trade Name
CLEARFIELD™
Trait
Imidazolinone herbicide tolerance.
Trait Introduction
Chemically induced seed mutagenesis
Proposed Use

Production for human food, livestock feed and industrial uses.

Product Developer
BASF Inc.

Summary of Regulatory Approvals

Country Food Feed Environment Notes
Canada 2006 2006

Introduction Expand

Rice lines IMINTA 1 and IMINTA 4 were developed to be tolerant to imidazolinone herbicides to provide an alternative strategy for weed control in rice. Imidazolinone herbicides are active against the acetolactate synthase (ALS) enzyme in plants, which 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.

The development of these events was acomplished by mutagenesis and the herbicide tolerance results from a single point mutation in the ALS gene (also known as acetohydroxyacid synthase or AHAS), such that the resulting enzyme has a single amino acid substitution and is no longer affected by imidazolinone herbicides. Previously authorized rice events CL121, CL141, CFX51 and PWC16 also contain modified ALS genes conferring tolerance to imidazolinone herbicides.

Summary of Introduced Genetic Elements Expand

Code Name Type Promoter, other Terminator Copies Form
als acetolactate synthase MUT native Whole plant selection of imidazolinone tolerant mutants, followed by introgression of HT trait into commercial varieties through cross-breeding.

Characteristics of Oryza sativa (Rice) Expand

Center of Origin Reproduction Toxins Allergenicity
Northern India and Southeast Asia, and southern China are believed to be the centre of origin of Asian rice (O. sativa). Wild progenitors of African cultivated rice (O. glaberrima) are grasses endemic to West Africa. Basically an autogamous plant propagating through seeds produced by self-pollination. Cross pollination between wild species and O. sativa cultivars has been reported to occur in natural habitats. Antinutrients including phytic acid, trypsin inhibitor, hemagglutinins (lectins) are present in the bran fraction. Allergenic proteins, 14-15 kDa range, present in the albumin plus globulin protein fraction from rice endosperm. Major 16 kDa allergenic protein is a member of the alpha-amylase/trypsin inhibitor family of proteins.

Modification Method Expand

Rice lines IMINTA 1 and IMINTA 4 were developed through chemically-induced mutagenesis of rice variety IRGA 417 with sodium azide to exhibit tolerance to imidazolinone containing herbicides. Whole plant selection procedures were used to select these events.

Characteristics of the Modification Expand

The Introduced DNA

As these were products of chemically induced mutagenesis, there was no introduction or incorporation of heterologous DNA into the rice genome. The tolerance to imidazolinone-containing herbicides is due to a single point mutation within the ALS encoding gene such that the amino acid sequence of the mutated enzyme differs by one amino acid from that of the wild-type enzyme.

Genetic Stability of the Introduced Trait

Herbicide treatments performed over several generations demonstrated that the herbicide tolerance trait was stably inherited and expressed in events IMINTA 1 and IMINTA 4.

Expressed Material

There were no new novel proteins expressed. The level of expression of ALS within plant tissue is generally low (~0.001% of total protein in rice seed), and this level of expression was not altered because of the genetic modification. High pressure liquid chromotagraphy (HPLC) of protein extracts from unmodified and modified rice varieties did not indicate the expression of new proteins, or altered expression of existing proteins, as a result of the mutagenic event.

Environmental Safety Considerations Expand

Outcrossing

There are no sexually compatible species for rice in Canada. The wild “rice” which does occur in Canada (Zizania aquatica) is not sexually compatible with domesticated rice, Oryza sativa. In addition, these herbicide-tolerant lines will not be cultivated in Canada and if released, would not persist in the environment.

Weediness Potential

Rice is not adapted to the environmental conditions encountered in Canada. The vegetative vigour, time to maturity, and seed production, for these herbicide-tolerant lines were within the normal range of these parameters as measured for other commercial rice varieties. In unmanaged ecosystems, the herbicide-tolerant trait will not confer a competitive advantage and will not, in itself, render rice more weedy or invasive of natural habitats.

Secondary and Non-Target Adverse Effects

There are no anticipated changes in ecological toxicity that would adversely impact on other organisms within managed or unmanaged ecosystems.

Impact on Biodiversity

As these lines did not display altered weediness or plant pest potential, or potential to adversely impact non-target organisms, and will not be cultivated in Canada, there was no anticipated impact on biodiversity in Canada.

Food and/or Feed Safety Considerations Expand

Nutritional Data (Livestock Feed Purposes)

Data on fatty acid profiles, protein content, amino acid composition, crude fibre, ash, phytate, and moisture content were provided for grain samples from lines IMINTA 1 and IMINTA 4 and the parental variety IRGA 417 grown in two locations in Argentina. Comparisons of these parameters between the herbicide-tolerant lines and conventional variety revealed some statistically significant differences (lower crude fat and oleic acid levels and lower levels of panthothenic acid), but levels were all within the range for conventional rice varieties.

Toxicity and Allergenicity

The single amino acid change within the native ALS enzyme was not anticipated to have any effect on the potential toxicity or allergenicity of this protein. The unmodified form of this enzyme does not display amino acid sequence homology with known protein toxins or allergens. The modified ALS protein from IMINTA 1 and IMINTA 4 was shown to be rapidly inactivated by heat (1 minute at 100°C) and equivalent to the parental controls with respect to trypsin degredation. Susceptibility to heat inactivation and sensitivity to proteolytic degradation are not characteristics of known protein toxins or allergens.

Measurements of the concentrations of normally occurring rice antinutritional factors (e.g., phytic acid and trypsin inhibitor) did not reveal any differences between these herbicide-tolerant lines and the parental rice variety. For all of the lines, the concentrations of trypsin inhibitor were below the threshold of detection.

Abstract Collapse

This product was not subject to regulation in any jurisdiction except Canada since the development of this herbicide-tolerant line did not employ recombinant DNA technologies. In Canada, regulatory approval was required for use in human food and livestock feed, but not for environmental release as these lines were not intended for cultivation in Canada.

Rice (Oryza sativa L.) was grown as a commercial crop in more than 100 countries with a combined harvest of 630 million metric tonn in 2006. The major producers of rice were China, India, Indonesia, Bangladesh, Viet Nam, Thailand and Myanmar. Rice is grown primarily for its grain, which is the staple food for half of the world’s population, and has many uses in the food and industrial sectors, including use in livestock feed.

Harvested rice, or rough rice, is encased by an inedible hull or husk, which is removed before milling. The hulls are utilized as fuels, mulch, abrasives and animal feed products. Brown rice is what remains after the hulls are removed. The light brown colour of brown rice is due to the presence of bran layers and the rice germ surrounding the rice kernel. Brown rice can be milled into regular white or ‘polished rice’, where white rice is distinguished by the fact that the hulls, bran layers and rice germ are removed. The bran and rice germs are high in protein and nutrients and are used in specialty foods such as rice bran oil and also in livestock feed. Both brown and white rice kernels can be parboiled and/or milled into rice flour for use in breakfast cereals, baby foods and desserts and numerous other food products. Rice kernels are also used to produce beer and rice wine.

Weeds are a significant production problem in rice cultivation. Weeds of rice producing areas, such as the United States, include red rice (Oryza spp.), barnyard grass, sprangletop, fall panicum, large crabgrass, rice flatsedge, yellow nutsedge, and smartweed. These are typically managed using a combination of cultural practices (e.g., dry vs wet tillage, using clean seed, crop rotations) and chemical controls (herbicides such as molinate and propanil).

Rice lines IMINTA 1 and IMINTA 4 were developed through chemical mutagenesis of the rice variety IRGA 417 with sodium azide to exhibit tolerance to imidazolinone containing herbicides. Imidazolinone herbicides are active against the acetolactate synthase (ALS) enzyme in plants, which 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.

Links to Further Information Expand


This record was last modified on Friday, March 26, 2010