Transfer and expression of the introduced genes for herbicide tolerance and a hybrid breeding system to other canola plants could increase the weediness potential, or alter the potential allergenicity and/or toxicity of the resulting plants.
As discussed in Risk scenario 1, allergenicity to people and toxicity to people and other organisms are not expected to be changed in the hybrid GM canola plants by the combination of introduced genes. This will also be the case if the introduced genes are expressed in other GM or non-GM canola plants.
As discussed in Risk scenario 2, the genes introduced into the hybrid GM canola plants are not expected to alter the tolerance of plants to biotic or abiotic stresses that normally restrict geographic range and persistence of canola in natural habitats. Similarly, they would not be expected to alter the geographic range or persistence of other canola plants if the introduced traits were transferred to their progeny.
However, the two herbicide tolerance genes present in the GM canola plants would confer a selective advantage in areas where the corresponding herbicides are applied. This would also be true if the traits were conferred to other canola plants in the environment.
In the broad-acre field situation, cross pollination between the hybrid GM canola proposed for release and other canola would be most likely to occur when canola crops are grown in adjacent paddocks and flower synchronously. Cross pollination may also occur where volunteer plants emerge after canola crops are harvested and develop to flowering stage, or where feral canola populations, resulting from seed being dispersed off-farm, establish along roadsides adjacent to cropping land where canola is planted.
Gene transfer to GM canola
Gene transfer could occur to other GM canola approved for either commercial or limited and controlled release. These include:
Limited and controlled releases under DIRs 032/2002, 069/2006, 103, 104 and 105
Commercial releases under DIR 020/2001 (Roundup Ready® canola) and DIR 021/2002 (InVigor® canola)
The commercially approved GM canolas are the parent lines of the GMOs proposed for release. Outcrossing of InVigor® x Roundup Ready® to these commercially approved GM canola plants would result in plants highly similar to the GMOs proposed for release. Therefore, any adverse outcomes expected for those progeny would be comparable to InVigor® x Roundup Ready® canola.
Licence conditions for limited and controlled GM canola releases include measures to restrict gene flow. Additionally, controls placed on GM canola released under limited and controlled conditions include not using the GMOs in food or feed and destroying any GMOs and volunteer plants in the areas of the release in accordance with the licence. Therefore, the potential for any adverse outcome from gene transfer to these limited and controlled releases of GM canola as a result of the proposed dealings is considered negligible.
Gene transfer to non-GM, non-herbicide tolerant canola plants would result in plants highly similar to the GMOs proposed for release or to their GM parents approved under DIR 020/2002 and 021/2001. Therefore, any adverse outcomes expected for those progeny would be comparable to InVigor® x Roundup Ready® canola or their parental GM canola lines. The control of glyphosate tolerant and glufosinate ammonium tolerant canola volunteers that occur as a result of gene transfer from InVigor® x Roundup Ready® canola crops represents an agricultural production issue with potential economic impact in terms of alternative weed management choices. There are a range of alternative herbicides assessed and approved by the APVMA which can be used to control GM canola volunteers in addition to mechanical means.
Gene transfer to non-GM herbicide tolerant canola
There are two conventionally bred herbicide-tolerant canola varieties currently being widely grown in Australia – triazine tolerant (TT) and imidazolinone-tolerant (Clearfield®). Where canola varieties that are tolerant to different herbicides have been commercially planted in close proximity, the production of multiple-herbicide resistant volunteers has been noted (Hall et al. 2000; Beckie et al. 2003). Gene transfer from InVigor® x Roundup Ready® canola to non-GM herbicide tolerant canola could result in the stacking of genes for tolerance to up to four different herbicide groups. Although InVigor® canola has not been commercially grown in Australia, this stacking of four herbicide tolerance traits has been a possibility since the approval of InVigor® canola and Roundup Ready® canola in 2003. Stacking was considered in the RARMPs for DIR 020/2002 and 021/2002 and was assessed to pose negligible risks. However, if InVigor® x Roundup Ready® canola were commercialised, development of canola plants with all four herbicide tolerance traits would be more likely, as it would require only two rather than three separate hybridisation events.
Apart from being tolerant to additional herbicides, such stacked GM canola is not expected to differ from the parental GM and non-GM varieties. There is no evidence or reasonable expectation that the non-GM herbicide tolerance traits would interact with the introduced genes from the GM canola proposed for release leading to changes in toxicity, allergenicity or weediness.
Multiple-herbicide tolerant individuals are as susceptible to alternative herbicides as are single-herbicide tolerant canola plants or their non-GM counterparts (Senior et al. 2002; Beckie et al. 2004; Dietz-Pfeilstetter & Zwerger 2009). In laboratory studies, multiple-herbicide tolerant canola plants were no more competitive than single-herbicide tolerant controls (Simard et al. 2005). Therefore, if multiple-herbicide tolerant canola plants were to occur, they are unlikely to be more invasive or persistent than non-herbicide tolerant or single-herbicide tolerant canola plants and could be controlled by other herbicides or other (non-chemical) agricultural practices.
Management of the impacts of gene transfer from InVigor® x Roundup Ready® canola to other canola can be achieved by the application of the already established principles and practices for minimising the development of herbicide resistance in any agricultural weeds: attention to the control of volunteers; informed selection and rotation of herbicides and crops; maintenance of hygiene in seeding, harvesting and transport operations; and implementation of good agronomic practices (Rieger et al. 2001; Downey 1999; Salisbury 2002c). These measures are incorporated in the Crop Management Plans that growers of InVigor® canola or Roundup Ready® canola are obliged to follow, and which will be implemented for InVigor® x Roundup Ready® canola.
While the control of canola with multiple herbicide tolerance traits may represent an agricultural production issue with potential economic impacts in terms of alternative weed management choices, there remains a range of approved herbicides and non-chemical methods of control.
Conclusion: The potential for allergenicity in people, or toxicity in people and other organisms, or increased weediness due to expression of the introduced genes in other canola plants as a result of gene transfer is not identified as a risk that could be greater than negligible. Therefore, it does not warrant further detailed assessment.
