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A Report on a Paper Concerning the Potential for Transgenic Weed Beets to Arise as a Consequence of Gene Transfer with Genetically Modified Sugar Beet
Advice of the Advisory Committee on Releases to the Environment
under Section 124 of the Environmental Protection Act 1990
September 2002
ACRE was asked to review the study by Benoît Desplanque, Nina Hautekèete and Henk Van Dijk (2002) 1 concerning the potential formation of transgenic weed beet.
This study considered non-GM sugar beet growing in the sugar producing region of northern France and data from non-GM sugar beet grown for seed further south. This information was used to discuss the probability of transgene transfer to weed beet if GM sugar beet is grown.
The authors quantified the current weed beet population in fields in the sugar producing region in the north of France and examined the extent that gene flow is possible between cultivated beet, weed beet and any wild (ruderal) beet present in this area. Sugar beet is a biennial plant that produces a swollen root in its first year and generally does not flower until its second year. However, if an allele of a gene conferring premature bolting is introduced into cultivated sugar beet from wild relatives these plants can eventually become weed beets. The potential for this particular allele to transfer from wild beet populations to cultivated varieties was studied rather than the transfer of transgenes from sugar beet plants to wild relatives.
The authors also used data from the sugar beet seed producing region in the south of France to assess how three key factors impact on gene flow between cultivated crops and their wild and weed relatives. These factors are concerned with the characteristics of the parental line into which the transgene is inserted. Sugar beet is self incompatible; therefore seed is produced by crossing a variety that produces pollen with a seed bearing line (that is male sterile). The authors suggest that gene flow from a GM herbicide resistance crop would be best retarded if the transgene was inserted into a tetraploid pollinator breeding line. They consider that the eventual formation of transgenic weed beets is probable, but the speed and scale at which this happens will depend upon the characteristics of the sugar beet line into which it is inserted.
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ACRE's advice ACRE felt that the study was important and useful when considering factors that can reduce gene flow between GM forage/sugar beet and wild and weed relatives. The committee welcomed the publication of this paper with its detailed discussion of new data. However, the flow of genes between cultivated beet and wild and weed relatives is long established and there have been a number of research articles published on the subject. In fact, it was pointed out in the first GMO research report (Raybould and Gray, 1994 2) commissioned by the Department of the Environment that crop beets are fully inter-fertile with both sea beet (Beta vulgaris ssp. maritima) and annual weed beet (Beta vulgaris). Because of this potential for cross-hybridisation between GM beet and its wild and weed relatives, ACRE has insisted on stringent risk management of all field trials of forage/sugar beet with the destruction of plants that bolt prematurely. Consent to grow beet in the Farm Scale Evaluations also includes this requirement to prevent flowering. The results presented in this paper reinforce ACRE's earlier conclusions. ACRE's risk assessment has always assumed that gene flow will occur if GM beet is grown on a commercial scale and as such, considers the potential consequences of this happening. In the case of herbicide tolerance, ACRE has been clear that this is essentially an agronomic problem. The trait is unlikely to confer a fitness advantage to sea beet (which is perennial and confined to coastal habitats where herbicides are not applied) but, if transferred to annual weed beets, would compromise the use of that particular herbicide in weed control. In fact, as Desplanque et al point out, transfer of a gene conferring herbicide tolerance to weed beet would bring us back to the current situation where control of weed beet in beet fields can be difficult and expensive. The paper is particularly helpful in suggesting ways of slowing down gene transfer to weed beet and thus maintaining the efficacy of the herbicide tolerance system. In particular, Desplanque et al suggest the insertion of transgenes into a tetraploid pollinator breeding line. |
1 Benoît Desplanque, Nina Hautekčete and Henk Van Dijk (2002). Transgenic weed beets: possible, probable, avoidable? Journal of Applied Ecology 39: 561-571.
2 Raybould A.F. and Gray A.J. (1994). Genetically modified crops and their wild relatives - a UK perspective. Department of the Environment. Research Report No. 1. Genetically Modified Organisms Research Report.