Database Product Description
- Host Organism
- Brassica napus (Argentine Canola)
- Trade Name
- Westar OXY-235
Herbicide tolerant, oxynil.
- Trait Introduction
- Agrobacterium tumefaciens-mediated plant transformation.
- Proposed Use
Production for human consumption and livestock feed.
- Product Developer
- Aventis CropScience (formerly Rhône Poulenc Inc.)
Summary of Regulatory Approvals
Summary of Introduced Genetic Elements Expand
Characteristics of Brassica napus (Argentine Canola) Expand
Donor Organism Characteristics Expand
Modification Method Expand
Characteristics of the Modification Expand
Environmental Safety Considerations Expand
Food and/or Feed Safety Considerations Expand
Argentine or oilseed rape (Brassica napus) was grown as a commercial crop in over 50 countries, with a combined harvest of 48.9 million metric tonnes in 2006. The major producers of rapeseed are China, Canada, India, Germany, France, the United Kingdom and Australia. Canola is a genetic variation of B. napus that was developed through conventional breeding to contain low levels of the natural rapeseed toxins, glucosinolate and erucic acid. Canola is grown for its seed, which represents a major source of edible vegetable oil and is also used in livestock feeds.
The only food use of canola is as a refined oil. Typically, canola oil is used by itself as a salad oil or cooking oil, or blended with other vegetable oils in the manufacture of margarine, shortenings, cooking and salad oils. Canola meal, a byproduct of the oil production process, is added to livestock feed rations. An increasing amount of oil is being used for biodiesel production, especially in Europe.
The removal of weeds early in the growing season is extremely important in canola production. Young canola seedlings are not very competitive and early weed pressure has detrimental effects on final yield. Precautions such as pre-plant tillage or herbicide application are common approaches for reducing weed competition. Once established, canola forms a dense canopy and is very competitive, making weed control less of a concern.
Line Oxy-235 (ACS-BNØ11-5) was developed to allow the use of oxynil herbicides, ioxynil and bromoxynil, as weed control options in canola. Bromoxynil is very effective on broadleaf weeds that are common in canola fields and the deployment of transgenic bromoxynil-tolerant canola will allow the post-emergence control of these weeds without crop injury.
Transgenic Oxy-235 contains a single copy of the bxn gene isolated from the bacterium Klebsiella pneumoniae (sub. sp ozaenae), which encodes a nitrilase enzyme that hydrolyzes oxynil herbicides to non-phytotoxic compounds. Constitutive expression of the bxn gene was regulated via the 35S promoter from cauliflower mosaic virus (CaMV) and levels of nitrilase enzyme were detected in samples of leaf (1000 ng/mg total protein) and seed (The Oxy-235 line was field tested in Canada from 1992 to 1996 and assessed for a number of agronomic characteristics, including seed yield, days to maturity, silique shattering, and overwintering capacity. In comparison with non-transgenic commercial canola varieties, all of these parameters were within the normal range of expression. Stress adaptation was evaluated, including resistance to major B. napus pests such as the fungal pathogen Leptosphaeria maculans (blackleg) and the susceptibility of Oxy-235 was within the ranges currently displayed by commercial varieties. The only significant difference between Oxy-235 canola and the parental non-transformed variety was that Oxy-235 exhibited field tolerance to ioxynil and bromoxynil.
As the nitrilase protein was not found in the refined oil produced from transgenic canola Oxy-235, it can be concluded that there will be no human exposure to this proteins. The genetic modification of Oxy-235 canola will not result in any change in the consumption pattern for this product.
Further studies were conducted to assess the potential toxicity of the introduced nitrilase protein. These included an acute oral toxicity study in mice, amino acid sequence comparisons with known protein toxins, an evaluation of the prior human history of ingestion of similar enzymes and the potential toxicity of bromoxynil metabolites. None of these studies indicated a potential for human toxicity. Similarly, studies on digestive fate (stability to pepsin digestion) and similarity to known allergens demonstrated that the nitrilase enzyme is rapidly degraded (<= 15 s upon exposure to simulated gastric fluid) and has no homology with known allergens.
Links to Further Information Expand
This record was last modified on Friday, March 26, 2010