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

Abstract

The potential commercialization of genetically modified herbicide-tolerant (GMHT) oilseed rape in Europe raises various concerns about their potential environmental and agronomic impacts, especially those associated with the escape of transgenes. Pollen of oilseed rape can be dispersed in space, resulting in the fertilization of sympatric compatible wild relatives (e.g. Brassica rapa) and oilseed rape cultivars grown nearby (GM and/or non-GM Brassica napus). The spatial and temporal dispersal of seeds of oilseed rape may lead to feral oilseed rape populations outside the cropped areas and oilseed rape volunteers in subsequent crops in the rotation. The incorporation of a HT trait(s) may increase the fitness of the recipient plants, making them more abundant and persistent, and may result in weeds that are difficult to control by the herbicide(s) to which they are tolerant. Vertical gene flow from transgenic oilseed rape to non-GM counterparts may also have an impact on farming and supply chain management, depending on labelling thresholds for the adventitious presence of GM material in non-GM products. Given the extent of pollen and seed dispersal in oilseed rape, it is obvious that the safe and sound integration of GMHT oilseed rape in Europe may require significant on-farm and off-farm management efforts. Crucial practical measures that can reduce vertical gene flow include (1) isolating seed production of Brassica napus, (2) the use of certified seed, (3) isolating fields of GM oilseed rape, (4) harvesting at the correct crop development stage with properly adjusted combine settings, (5) ensuring maximum germination of shed seeds after harvest, (6) controlling volunteers in subsequent crops, and (7) keeping on-farm records. The implementation of the recommended practices may, however, be difficult, entailing various challenges.

Regulating coexistence of GM and non-GM crops without jeopardizing economic incentives

“…In scientific and regulatory communities, the debate about coexistence has been centered mainly on the following aspects: preventive coexistence measures needed to keep the adventitious presence of GM material in non-GM products below established tolerance thresholds [5,[7][8][9][10][15][16][17][18]; the feasibility and costs of implementing such measures [16,[19][20][21][22][23]; segregation costs and potential economic losses resulting from adventitiously co-mingled products [24][25][26]; who should bear the costs of coexistence measures [2,14]; and who should redress the incurred economic losses due to adventitious mixing [13]. Although these aspects are of fundamental importance when discussing coexistence strategies, they do not take into account the economic incentives for coexistence.…”

“…In agriculture, various sources can lead to the unintentional presence of GM material in non-GM products. Such sources include the following: the use of impure seed; cross-fertilization due to pollen flow between neighboring fields; the occurrence of volunteer plants originating from seeds and/or vegetative plant parts from previous GM crops; mixing in machinery during sowing, harvest and/or post-harvest operations; and, to a lesser extent, cross-fertilization from certain sexually compatible wild relatives and feral plants [5][6][7][8][9][10].…”

Ethics in the Societal Debate on Genetically Modified Organisms: A (Re)Quest for Sense and Sensibility

“…To ensure the co-existence between cropping systems, national and/or regional authorities now are developing legal co-existence frames in which various on-farm management measures are set (e.g., Devos et al, 2004Devos et al, , 2005Devos et al, , 2007, and in which liability provisions for economic damage are assigned. 12 However, this appears to be an extremely difficult task.…”

Using an oilseed rape x wild /weedy relative gene flow index for the monitoring of transgenic oilseed rape

“…Finally, the transgene (6) should persist in natural / weedy populations. Information on step 2 to 6 was retrieved from literature and reviewed for oilseed rape relatives found in Belgium (Devos et al, 2004 and2007). Next to flowering characteristics, focus was put on hybridisation frequencies, fitness parameters of hybrids and their progeny, the transgene and on management practices, as these all play a crucial role in achieving introgression.…”