Transgenic crops : new weed problems for Canada?

Abstract

Over 25 000 transgenic field trials were conducted globally from 1986-1997, and many transgenic crops, including soybean (Glycine max), maize (Zea mays), tobacco (Nicotiana tabaccum), cotton (Gossypium hirsutum), canola (Brassica napus, B. rapa), tomato (Lycopersicon esculentum) and potato (Solarium tuberosum) have been commercially released. There has been a high adoption rate, with at least 28 million ha reported for 1998, with herbicide- and insect-resistant plants occupying 71 and 28% of the releases, respectively. The current status of commercial production of transgenic crops in Canada is summarized. Transgenic crops have the potential to change weed communities/populations in three principal ways, via: 1 ) escape and proliferation of the transgenic plants as 'weedy' volunteers with subsequent displacement of the crop, weed and/or natural vegetation; 2) hybridization with and transgene infiltration into related weedy and/or wild species, resulting in invigorated weeds and/or alteration of natural gene frequencies in these species; and 3) genetic changes in populations of unrelated species, as a result of changes to the environment, in particular herbicide-resistant (HR) transgenic crops and the development of HR weeds. Potential risk can be estimated a priori using knowledge of the systematics of crop/wild/weed complexes. Risk must be assessed on a case-by-case basis for each crop, each country/ecological region, and for each trait. Potential weed risks will be greater if crop volunteers are predisposed to becoming weedy, are well adapted to the Canadian climate and if sexually compatible wild species are present.

Management of herbicide-tolerant oilseed rape in Europe: a case study on minimizing vertical gene flow

“…Successful recruitment of oilseed rape from seed mainly depends on its ability to compete for space with primary colonizers, particularly perennial grasses. In most non-agricultural areas oilseed rape lacks the ability to survive due to the absence of competition-free gaps (Crawley et al, 1993;Warwick et al, 1999). Populations that have established outside the agricultural fields often go extinct after 2 to 4 years (Crawley and Brown, 1995;Crawley et al, 2001;Norris and Sweet, 2002), but other studies suggest that feral oilseed rape populations can persist far longer (8-10 years) (Lutman et al, 2004;Pessel et al, 2001;Squire et al, 2003;Wilkinson et al, 1995).…”

Impact environnemental des cultures transgéniques

“…En milieu agricole, l'introgression d'un transgène de tolérance à un herbicide pourra par exemple s'avérer problématique en rendant plus difficile la lutte aux mauvaises herbes, alors que pourront apparaître au champ des hybrides tolérants à l'un ou plusieurs des herbicides contrés par l'expression des transgènes introduits (Beckie et al 2003;Hall et al 2000). Peu persistants en habitats naturels (Crawley et al 1993(Crawley et al , 2001) et sensibles aux herbicides couramment utilisés pour la répression des volontaires (Beckie et al 2004), ces hybrides tolérants pourraient néanmoins montrer un impact négatif sur le plan agronomique en affectant par exemple le choix des herbicides ou des rotations de culture dans les années subséquentes, ou en compromettant l'adoption d'une pratique agricole en émergence comme le semis direct (Légère 2005;Warwick et al 1999).…”

Feral genetically modified herbicide tolerant oilseed rape from seed import spills: are concerns scientifically justified?

“…7 | P a g e Oilseed rape is generally regarded as an opportunistic species, and not as an ecologically hazardous invasive species (Warwick et al, 1999). It can take advantage of disturbed sites due to its early germination potential and capacity to capture resources rapidly.…”

“…It can take advantage of disturbed sites due to its early germination potential and capacity to capture resources rapidly. In undisturbed natural habitats, oilseed rape lacks the ability to establish stable populations, possibly due to the absence of competition-free germination sites (Crawley et al, 1993(Crawley et al, , 2001Warwick et al, 1999;Hails et al, 2006;Damgaard and Kjaer, 2009). Moreover, in controlled sowings into road verges, field margins and wasteland, very few seedlings survived to maturity due to grazing (e.g., by molluscs) and abiotic stress (Charters et al, 1999).…”

“…Experiments and models on fitness differences between the GM plant and its non-GM counterpart (category 2 above) are usually inferred from a composite measure of relative plant germination, emergence, growth, survivorship, biomass and fecundity (Fredshavn et al, 1995;Warwick et al, 1999Warwick et al, , 2004Warwick et al, , 2009Norris and Sweet, 2002; Claessen et al, 2005a,b;Simard et al, 2005;Londo et al, 2010). Beckie et al (2004) showed that GMHT oilseed rape with single or multiple HT traits is not more persistent (weedier) than non-GMHT plants.…”