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EC-sponsored Research on Safety of Genetically Modified Organisms - A Review of Results
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image Study of gene dispersal from plants produced by recombinant DNA technology

Background and objectives

Genetic modifications (manipulation or engineering) and the introduction of new characters into crop plants has considerable potential for European agriculture. It is already possible to introduce genes which make crops resistant to certain pests and diseases and to improve the quality of the plant product, and many other new opportunities are emerging. Because genes from a wide variety of organisms and even synthetic genes produced in the laboratory can be introduced into crop plants, it is important to study their function in the modified plant. Most importantly, the biosafety aspects of any release into the environment must be carefully considered. The likelihood and consequences of the genes, and thus the traits, being transferred to other crop plants or related weed species is of particular concern.

Approach and methodology

The aim was to study the frequency and extent of cross-pollination between modified crop plants containing introduced marker genes, and other plants of either the same species or other related species, and particularly those that are common weeds. Three major crop species were used: potato, alfalfa and oilseed rape. Powerful techniques for transformation of these species are already available, and each illustrate specific safety aspects as concerns introduction into an open environment. Two major issues were addressed. First, the extent and distance of cross-pollination between modified plants and non-modified plants growing around them in an adjacent crop was examined. Oilseed rape was used for these experiments. Second, the ability of crop plants to transfer introduced genes to related species was considered. This also involved analysing the likelihood of the affected plants (especially weeds) becoming established in wild populations. Potato, alfalfa and oilseed rape were used. This study involved both natural outcrossing and the application of sophisticated technology to generate hybrids for evaluation.

image Potatoes.

ain findings and outcome

A marker gene, the gene for resistance to a particular herbicide, was introduced into alfalfa. The gene was transferred from the modified plants to other alfalfa plants and also to various related plants: M. sativa spp. falcata, M. sativa spp coerulea, M. sativa spp glutinosa, M. saxatilis and M. cancellata. The marker gene was inherited and expressed in the hybrid plants in accordance with standard genetic theory. In contrast, potato could not be crossed with local weed relatives black nightshade and bittersweet. Using appropriate sophisticated techniques, oilseed rape could be crossed with related wild species. Initial characterisation suggested that the hybrids expressed the transgene in a normal way. However, due to the hybrid nature of these plants, there were specific effects interfering with normal propagation (for example partial or complete sterility). Even under optimal conditions for interaction between oilseed rape and related weeds (mixed stands of the two plant species) the frequencies of outcrossing were very low. Indeed, no outcrossing was detected after screening many millions of individual plants. Field trials were used to estimate the distance of biologically relevant gene dispersal. At a distance of 4 metres from the pollen source, the frequency of outcrossing dropped to below 1 in 1000.


Gene transfer may occur between alfalfa and certain non-cultivated relatives growing nearby. In the conditions studied, the dispersal of transgenes by potato pollen is not possible and there is therefore no biosafety problem. Gene transfer from oilseed rape to certain non-cultivated relatives is possible by specific experimental techniques, but extremely unlikely in natural conditions. Furthermore, such hybrids do not persist in the environment. The range for biologically relevant dispersal of pollen from oilseed rape is short where suitable biological containment measures are used (for example guard rows of cultivated plants).


Major publications

Scheffler J.A., Parkinson R. & Dale P.J., "Frequency and distance of pollen dispersal from transgenic oilseed rape (Brassica napus)".
Transgenic Research, 2, 1993, pp. 356-364.

Dale P.J., Irwin J.A. & Scheffler J.A., "The experimental and commercial release of transgenic crop plants".
Plant Breeding, 111, 1993, pp. 1-22.

Dale P.J., "The impact of transgenes in hybids between genetically modified crop plants and their related species - general considerations".
Molecular Ecology, 3, 1994, pp. 31-36.

McPartlan H.C. & Dale P.J., "An assessment of gene transfer by pollen from field-grown transgenic potatoes to non-transgenic potatoes and related species".
Transgenic Research, 3, 1994, pp. 216-225.

Scheffler J.A. & Dale P.J., "Opportunities for gene transfer from transgenic oilseed rape (Brassica napus) to related species".
Transgenic Research, 3, 1994, pp. 263-278.

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imageResearch project

Contract number

February 1989 – December 1990

P.J. Dale
John Innes Centre of Plant Science Research
Norwich (UK)



W. De Greef
PGS Plant Genetic Systems N.V.
Gent (BE)

M. Renard
Le Rheu (FR)

W.J. Stiekema
Centre for Plant Breeding Research
Wageningen (NL)

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