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Biotechnology, Food, Agriculture, Public policy and Consumer Concerns
Phytosfere'99 - Highlights in European Plant Biotechnology Gert E. de Vries and Karin Metzlaff (Editors). 9 Elsevier Science B.V. All rights reserved.
Biotechnology, Food, Agriculture, Public policy And Consumer Concerns Introduction
Since 20 years genetic engineering is being discussed. Since the very beginning there have been serious concerns, also by the scientists involved in the first GMO experiments. Since then, billions of dollars have been invested in the development in the different application fields and millions of dollars in public education and acceptance. An international analysis of associated risk research or research on possible ecological and health impact came to the conclusion that less than 1% of the world wide development budget has been used for research regarding safety aspects [1]. The consumer and the public as a whole feels more and more ill at ease given these facts. There is more and more distrust in industry and in the regulatory framework, because what they say and how they try to assure the public does not fit the facts. For me, dealing with risk assessment in genetic engineering since 15 years, there is an extreme contradiction between the emerging data and the handling of these data in the context of evaluation and decision making. It is obvious that having different value systems and different interests, scientists, the public, industry representatives and others may come to different conclusions based on the same facts. The problem seems to be how to integrate these different evaluations in a fair and impartial manner in decision processes. I like to discuss - as examples - two areas of concerns in more detail. But before doing that I like to give a short overview on the main questions concerning ecological or health impacts. Main
areas of concern
- cross-hybridisation with related species/weeds (example canola: [2-5]) - horizontal gene transfer [6] resulting in uncontrolled spread of new gene combinations - rapid resistance development of important plant pathogens to biological pest-management tools with an accompanying destruction/exhaustion of the naturals means to defend against pests and pathogens (resulting in an even greater dependence on chemical pest control in the long term) [7] - problematic impacts on non-host organisms (examples: reduced fertility in lady bugs when fed with aphids who ingested bt-containing plant sap [8], toxic impacts of corn-borer larvae on lacewing-flies [9])
Beatrix Tappeser, Institute for Applied Ecology, Freiburg, Germany
37
Opportunities and Challenges -
-
development of new virus combinations using virus resistant plants [ 10, 11] pleiotropic and position-effects influencing ecological traits and/or digestibility of the plants (see Pusztai case) allergenicity [ 12, 13] horizontal transfer of antibiotic resistance genes [ 14]
Some of these concerns are interconnected. For example it is known that proteinase-inhibitors very often have allergenic potential and belong to the set of proteins which cause certain plant to be allergenic to sensitive people [ 15]. Different proteinase-inhibitors are being cloned in a wide range of crop plants to confer insect-resistance. It has been shown that proteinase-inhibitors have the potential to harm benefical insects such as bees, inpairing their ability to recognise flower smells and shortening their lives [ 16]. Being a biologist especially such effects make me very concerned. The long term impact of less or even lack of pollination capacity in nature may be enormous. Many of our fruit trees and vegetables, but also a lot of other plants are dependent on insect pollination as the main possibility of pollen transfer for fruit and seed production. Until now we could take such service by insects for granted. What would it mean - for agricultural production, for the functioning of ecosystems, for biological diversity as a whole, if there will be a wide range of different crop plants producing such proteins. There will be no quick answer but lots of questions and concerns. Given our absolute dependence on agriculture for food production precaution should precedent any other evaluation scheme. We have too few knowledge to take a responsible decision now. The example given indicates possible problems that we may face a long way down the road we have already taken. Although allergenicity problems are known and there are hints for serious non-target impacts the perceived economic benefits seem to be big enough to continue along this path of development.
Horizontal
gene
transfer
Another question of great concern is the possibility of spread of the new recombinant sequences via horizontal gene transfer. It was one of the first questions raised after the creation of the first transgenic microorganism by Paul Berg and collaborators. It is exactly 25 years ago that Paul Berg and others published their famous letter ,,Potential Biohazards of Recombinant DNA Molecules" in Science [17]. Amongst others, they were especially worried about horizontal gene transfer of antibiotic resistance genes. Since then the likelihood of gene transfer events has been heavily debated. The main assumptions had been that the probability would be extremely low because of highly restricted transfer under natural conditions. As additional support it was stated that DNA released into the environment or in the digestive tract would be quickly and easily degraded. Since the end of the seventies the message for any risk assessment has been: Don't worry about horizontal gene transfer. There is almost no chance for this to happen. Both assumptions on gene transfer possibilities and on DNA stability have been proven wrong. DNA is quite stable in different environments and transfer events can be demonstrated under different conditions [18]. Even the long doubted transfer of recombinant plant genes to bacteria could be shown to occur under laboratory conditions [6]. 38
Public policy and consumer concerns Another area of concern is horizontal gene transfer in the gastrointestinal tract of insects and vertebrates. In contrast to earlier, long standing views, DNA is not quickly fragmented in the intestine but instead remains stable for a surprisingly long period. Moreover, DNA ingested with food can be excreted after only partial digestion. DNA can also pass into the bloodstream to be taken up by leukocytes and cells of the liver and spleen [ 19, 20]. The quoted experiments were performed on naked DNA, while DNA ingested with food is normally complexed with proteins and thus better protected. Beside this, the environment of the human or animal gastrointestinal tract changes in the course of digestion depending on what types of food are eaten together. This means that the resistance of proteins or DNA to digestion is not always constant but may vary. Laboratory experiments on the degradability of DNA in synthetic gastrointestinal liquids, as they are usually carried out in studies on transgenes, do not take such effects into account because they use a constant pH and purified DNA [ 10, 21 ]. Recently it has even been possible to demonstrate "natural" transformation in an artificial mammalian gastrointestinal model. [22] Such evidence has been available some 15 years when Orpin et al. [23] were able to show that Selenomonas ruminantium, a bacterial species inhabiting the bovine gastrointestinal tract, is naturally transformable. Furthermore, Tebbe et al. [24] reported that gene transfer can occur from orally administered GMMs to various recipients (Arthrobacteria) via transformation in the intestine of springtails (Folsomia candida). Perreten et al. [14] documented the development of a plasmid carrying multiple antibiotic resistances which they had isolated from raw milk cheese. These resistances originated from four different microorganisms and probably developed through the action of antibiotics in the microflora of the lactating cows. The authors take a clear stance on the issue: "To preserve the life-saving potential of antibiotics, the spread of resistance genes at all levels must be stopped. Distribution routes like those between animals, food and consumers have to be interrupted." ([14], p.802). Only recently transformation events in an artificial mammalian gastro-intestinal tract could be detected with a probability of one in 10 million. Given the billions of bacteria inhabiting our intestine that is not really a rare event. [22].
Vertical gene transfer Another central issue that has featured in discussions on the cultivation of transgenic plants since its very beginning is that of outcrossing from such plants and introgression of the recombinant genes to related weed and wild plants. It was more or less accepted, at least in the beginning of the debate, that spread of transgenes should be avoided as best possible, as this may have problematic effects on the composition of wild flora and biocoenoses in general. A further point now attracting increasing attention are the implications of resistance development through outcrossing (e.g. herbicide resistance or insect resistance), as this may not only have consequences for non-cultivated ecosystems but in particular also for agricultural land use systems. The results of hybridisation experiments clearly demonstrate the possibility of a gene flow from rape to wild herb populations. Potential hybridisation partners of Brassica napus are not only to be found in the genus of Brassica but also in other groups of the mustard family [25]. Potential hybridisation partners of rape include in particular wild herbs, which are probably 39
Opportunities and Challenges all subject to a high degree of cross-fertilisation. According to Darmency [26] this crossfertilisation facilitates the transmission of transgenes from rape to associate herbs. Under field conditions rape has proven capable of hybridisation with wild turnip (Brassica rapa), brown mustard (Brassicajuncea), black mustard (Brassica nigra) hoary mustard (Hirschfeldia incana, synonymous with Brassica adpressa), wild radish (Raphanus raphanistrum) and wild mustard (Sinapis arvensis) [27]. All experience and data gained in the course of the past years point to a high probability of rape populations prevailing outside cultivated areas and the possibility of gene flow to nontransgenic populations and related wild herbs. Many of Europe's major crop species have been equipped with identical herbicide resistance genes. Their large-scale use will therefore produce an enormous selective pressure towards corresponding resistant weeds. While rape will be the plant to initiate rapid resistance development, other plants equipped with the same resistance but lacking crossable wild relatives in the region will sustainably promote the onesided selection of weeds rendered resistant by the former. This development will also be accompanied by a further impoverishment in farmland-associated floral species and insects, because of the constantly increasing usage of broad-spectrum herbicides instead of selective herbicides. Furthermore, the cloning of multiple resistances into one and the same crop species also gives related wild herbs the opportunity to acquire multiple resistance. The largescale resistance management schemes now being discussed in anticipation of herbicide resistance problems may have to accommodate whole regions and extend over several rotation periods in order to be effective [28]. That will need a high planning and control effort. No less in conflict with the requirements of sustainability, and with the principles of sustainable utilisation and conservation laid down in the Convention on Biological Diversity, is the endangerment of species diversity entailed in the present herbicide resistance strategies. In the light of the knowledge on horizontal and vertical gene transfer that has accumulated during the past years, the rapid commercialisation of a multitude of herbicide-resistant transgenic plants also constitutes a violation of the precautionary principle. Speakers at international debates are often heard to invoke another principle, namely that decisions should only be made on the basis of scientific knowledge. There is no objection to this, just as long as such knowledge-based decisions really take account of all the relevant scientific evidence available. In concluding I would like to quote Heinemann : "The risk of genetically engineered organisms for commercial preparation is the potential for the engineered product to demonstrate unexpected "monster" qualities or for the genes to escape into the wild fauna and flora and thereby create genetic "monsters". These are risks which cannot be excluded with present data. The potential for escape of a resistance gene introduced into the genome of a commercially desirable plant cannot be gauged by small-scale gene escape experiments. By known examples of gene transfer frequencies in nature, the potential for exchange is too great to be excluded by argument. (...) What we know the least about is the nature of the evolutionary forces that determine the success or failure of monsters. We have limited or no predictive power for the fate of recombinant genes. In the case of an antibiotic resistance, we may be able to say that its known functions pose no additional threats. But we cannot be sure that its known functions are all of its potential functions either on its own or in conjunction with the 40
Public p o l i c y a n d c o n s u m e r concerns m a n y n o v e l g e n o m i c c o n t e x t s in w h i c h it m i g h t be f o u n d s h o u l d it be t r a n s f e r r e d horizontally. Therefore, as a qualitatively different t e c h n o l o g y , genetic e n g i n e e r i n g s h o u l d be c o m m e r c i a l i s e d w i t h e x t r e m e c a u t i o n until the a p p r o p r i a t e scientific e x p e r i m e n t s can be c o n d u c t e d " ([29], p.23).
References 1.
2.
3. 4. 5. 6. 7. 8. 9.
10. 11.
12. 13. 14. 15.
16. 17.
18. 19. 20.
Sukopp, H.; Sukopp, U. (1997): 0kologische Begleitforschung und Dauerbeobachtung im Zusammenhang mit Freisetzung und Inverkehrbringen gentechnisch ver~inderter Kulturpflanzen; edited by: Thtiringer Ministerium ftir Landwirtschaft, Naturschutz und Umwelt (TMLNU) in: Chancen und Risiken der Gentechnik im Umweltschutz; 43-51 Jorgensen, R.B., Andersen, B. (1994): Spontaneous hybridization between oilseed rape (Brassica napus) and weedy B. campestris (Brassicaceae). A risk of growing genetically modified oilseed rape. American Journal of Botany 12, 1620-1626 Mikkelsen, T.R., Andersen, B., Jorgensen, R.B. (1996) The risk of crop transgene spread. Nature 380, 31 Lefol, E.; Fleury, A.; Darmency, H. (1996): Gene dispersal from transgenic crops. II. hybridization between oilseed rape and the wild hoary mustard. Sexual Plant Reproduction 9 (4)189-196 Chevre, A.-M.; Eber, F.; Baranger, A.; Renard M. (1997): Gene flow from transgenic crops. Nature, vol.389, p.924 Gebhard, E; Smalla, K. (1998): Transformation of Acinetobacter sp. strain BD413 by transgenic sugar beet DNA. Applied and Environmental Microbiology 64 (4) 1550-1554 Mellon, M.; Rissler, J. (1998): Now or never: Serious New Plans to Save a Natural Pest Control, Union of Concerned Scientists (UCS) Birch, A. N. E.; Geoghegan, I. E.; Majerus, M. E. N.; Hackett, C; Allen, J (1997): Interaction between plant resistance genes, pest aphid populations and beneficial aphid predators. Soft fruit & perennial crops p.68-72 Hilbeck, A., Baumgartner; Fried, E M.; Bigler, E (1998): Effects of transgenic bacillus thuringensis corn-fed prey on mortality and development time of immature Chrysoperla carnea (Neuroptera: Chrysopidae); Environmental Entomology 27 (2) 480-487 Eckelkamp, C.; J~iger, M.; Weber, B. (1997): Risikotiberlegungen zu transgenen virusresistenten Pflanzen. Gutachten i. A. des Umweltbundesamts (UBA) Texte 59/97 Rubio, T.; Borja, M.; Scholthof, H. B.; Jackson, A. O. (1999): Restoration of wild-type virus by double recombination of tombusvirus mutants with a host transgene; Molecular Plant-Microbe Interactions 12 (2) 153-162 Nordlee, J. A.; Taylor, S. L.; Townsend, J. A.; Thomas, L. A.; Bush, R. K. (1996): Identification of a brazilnut allergen in transgenic soybeans. The New England Journal of Medicine 334 (11) 688-692 Nestle, M. (1996): Allergies to transgenic foods - questions of policy. The New England Journal of Medicine 334 (11)726-727 Perreten, V.; Schwarz, E; Cresta, L.; Boeglin, M.; Dasen, G.; Teuber, M. (1997): Antibiotic resistance spread in the food. Nature 389, 801-802 Franck-Oberaspach, S. L.; Keller, B. (1996): Produktsicherheit von krankheits- und sch~idlingsresistenten Nutzpflanzen: Toxikologie, allergenes Potential, Sekund~ireffekte und Markergene; in: Gentechnisch ver~inderte krankheits- und sch~idlingsresistente Nutzpflanzen. Eine Option ftir die Landwirtschaft? Band I, Materialien, Publikation des Schwerpunktprogramms Biotechnologie des Schweizerischen Nationalfonds, Bern Pham-Delegue, M.-H. (1997): Risk assessment of transgenic oilseed rape on the honeybee. Personal communication; see also: Sting in the tale for bees. New Scientist 16.8.1997 Berg, E; Baltimore, D.; Boyer, H. W.; Cohen, S. N.; Davis, R. W.; Hogness, D. S.; Nathans, D.; Roblin, R.; Watson, J. D.; Weissmann S.; Zinder, N. D. (1974): Potential biohazards of recombinant DNA molecules. Science, July 1974 vo1.185, p.303 Eckelkamp, C.; J~iger, M.; Tappeser, B. (1998): Verbreitung und Etablierung rekombinanter Desoxyribonukleins~iure (DNS) in der Umwelt. Gutachten i. A. des Umweltbundesamtes (UBA) Texte 51/98 Schubbert, R.; Lettmann, C.M.; Doerfler, W. (1994): Ingested foreign DNA persists in the gastrointestinal tract and enters the bloodstream of mice. Molecular and General Genetics 242, 495-504 Schubbert, R.; Renz, D.; Schmitz, B.; Doerfler, W. (1997): Foreign (M13) DNA ingested by mice reaches peripheral leucocytes, spleen, and liver via the intestinal wall mucosa and can be covalently linked to mouse
41
Opportunities and Challenges DNA. PNAS 94, 961-966 21. Eckelkamp, C.; J~iger, M.; Weber, B. (1997a): Antibiotikaresistenzgene in transgenen Pflanzen, insbesondere Ampicillin-Resistenz in Bt-Mais. Oko-Institut e.V., Freiburg. 22. New Scientist (1999): Gut reaction. 30 January (Debora MacKenzie) 23. Orpin, C.G.; Jordan, D.J.; Hazlewood, G.E; Mann, S.E (1986): Genetic transformation of the ruminal bacterium Selenomonas Ruminantium. J. Appl. Bacteriol. 61:xvi 24. Tebbe, C.C.; Vahjen, W.; Munch, J.C.; Feldmann, S.D.; Ney, U.; Sahm, H.G.; Amore, R.; Hollenberg, C.E (1994): f0berleben der Untersuchungsst~mme und Persistenz ihrer rekombinanten DNA. BioEngineering 6/ 94, 14-21 25. Scheffier, J.A., Dale, EJ. (1994) Opportunities for gene transfer from transgenic oilseed rape (Brassica napus) to related species. Transgenic Research 3, 263-278 26. Darmency, H. (1994): The impact of hybrids between genetically modified crop plants and their related species: introgression and weediness. Molecular Ecology 3, 37-40 27. Eckelkamp, C.; Mayer, M.; Weber B. (1997c): Basta-resistenter Raps. Vertikaler und horizontaler Gentransfer unter besonderer Beriicksichtigung des Standortes W61fersheim-Melbach. Werkstattreihe Nr. 100, Oko-Institut e.V., Freiburg. 28. Korell, M.; Schittenhelm, S.; Weigel, H.J. (1997): Aufstellen yon Kriterien ftir die nachhaltig umweltgerechte Nutzung gentechnisch ver~inderter Kulturpflanzensorten. Umweltbundesamt, Texte 88/97 29. Heinemann J.A. (1997): Assessing the risk of interkingdom DNA transfer. In: Nordic seminar on antibiotic resistance marker genes and transgenic plants. Norwegian Biotechnology Advisory Board (ed.), Oslo, 17-28
42
Biotechnology, Food, Agriculture, Public policy And Consumer Concerns Introduction
Since 20 years genetic engineering is being discussed. Since the very beginning there have been serious concerns, also by the scientists involved in the first GMO experiments. Since then, billions of dollars have been invested in the development in the different application fields and millions of dollars in public education and acceptance. An international analysis of associated risk research or research on possible ecological and health impact came to the conclusion that less than 1% of the world wide development budget has been used for research regarding safety aspects [1]. The consumer and the public as a whole feels more and more ill at ease given these facts. There is more and more distrust in industry and in the regulatory framework, because what they say and how they try to assure the public does not fit the facts. For me, dealing with risk assessment in genetic engineering since 15 years, there is an extreme contradiction between the emerging data and the handling of these data in the context of evaluation and decision making. It is obvious that having different value systems and different interests, scientists, the public, industry representatives and others may come to different conclusions based on the same facts. The problem seems to be how to integrate these different evaluations in a fair and impartial manner in decision processes. I like to discuss - as examples - two areas of concerns in more detail. But before doing that I like to give a short overview on the main questions concerning ecological or health impacts. Main
areas of concern
- cross-hybridisation with related species/weeds (example canola: [2-5]) - horizontal gene transfer [6] resulting in uncontrolled spread of new gene combinations - rapid resistance development of important plant pathogens to biological pest-management tools with an accompanying destruction/exhaustion of the naturals means to defend against pests and pathogens (resulting in an even greater dependence on chemical pest control in the long term) [7] - problematic impacts on non-host organisms (examples: reduced fertility in lady bugs when fed with aphids who ingested bt-containing plant sap [8], toxic impacts of corn-borer larvae on lacewing-flies [9])
Beatrix Tappeser, Institute for Applied Ecology, Freiburg, Germany
37
Opportunities and Challenges -
-
development of new virus combinations using virus resistant plants [ 10, 11] pleiotropic and position-effects influencing ecological traits and/or digestibility of the plants (see Pusztai case) allergenicity [ 12, 13] horizontal transfer of antibiotic resistance genes [ 14]
Some of these concerns are interconnected. For example it is known that proteinase-inhibitors very often have allergenic potential and belong to the set of proteins which cause certain plant to be allergenic to sensitive people [ 15]. Different proteinase-inhibitors are being cloned in a wide range of crop plants to confer insect-resistance. It has been shown that proteinase-inhibitors have the potential to harm benefical insects such as bees, inpairing their ability to recognise flower smells and shortening their lives [ 16]. Being a biologist especially such effects make me very concerned. The long term impact of less or even lack of pollination capacity in nature may be enormous. Many of our fruit trees and vegetables, but also a lot of other plants are dependent on insect pollination as the main possibility of pollen transfer for fruit and seed production. Until now we could take such service by insects for granted. What would it mean - for agricultural production, for the functioning of ecosystems, for biological diversity as a whole, if there will be a wide range of different crop plants producing such proteins. There will be no quick answer but lots of questions and concerns. Given our absolute dependence on agriculture for food production precaution should precedent any other evaluation scheme. We have too few knowledge to take a responsible decision now. The example given indicates possible problems that we may face a long way down the road we have already taken. Although allergenicity problems are known and there are hints for serious non-target impacts the perceived economic benefits seem to be big enough to continue along this path of development.
Horizontal
gene
transfer
Another question of great concern is the possibility of spread of the new recombinant sequences via horizontal gene transfer. It was one of the first questions raised after the creation of the first transgenic microorganism by Paul Berg and collaborators. It is exactly 25 years ago that Paul Berg and others published their famous letter ,,Potential Biohazards of Recombinant DNA Molecules" in Science [17]. Amongst others, they were especially worried about horizontal gene transfer of antibiotic resistance genes. Since then the likelihood of gene transfer events has been heavily debated. The main assumptions had been that the probability would be extremely low because of highly restricted transfer under natural conditions. As additional support it was stated that DNA released into the environment or in the digestive tract would be quickly and easily degraded. Since the end of the seventies the message for any risk assessment has been: Don't worry about horizontal gene transfer. There is almost no chance for this to happen. Both assumptions on gene transfer possibilities and on DNA stability have been proven wrong. DNA is quite stable in different environments and transfer events can be demonstrated under different conditions [18]. Even the long doubted transfer of recombinant plant genes to bacteria could be shown to occur under laboratory conditions [6]. 38
Public policy and consumer concerns Another area of concern is horizontal gene transfer in the gastrointestinal tract of insects and vertebrates. In contrast to earlier, long standing views, DNA is not quickly fragmented in the intestine but instead remains stable for a surprisingly long period. Moreover, DNA ingested with food can be excreted after only partial digestion. DNA can also pass into the bloodstream to be taken up by leukocytes and cells of the liver and spleen [ 19, 20]. The quoted experiments were performed on naked DNA, while DNA ingested with food is normally complexed with proteins and thus better protected. Beside this, the environment of the human or animal gastrointestinal tract changes in the course of digestion depending on what types of food are eaten together. This means that the resistance of proteins or DNA to digestion is not always constant but may vary. Laboratory experiments on the degradability of DNA in synthetic gastrointestinal liquids, as they are usually carried out in studies on transgenes, do not take such effects into account because they use a constant pH and purified DNA [ 10, 21 ]. Recently it has even been possible to demonstrate "natural" transformation in an artificial mammalian gastrointestinal model. [22] Such evidence has been available some 15 years when Orpin et al. [23] were able to show that Selenomonas ruminantium, a bacterial species inhabiting the bovine gastrointestinal tract, is naturally transformable. Furthermore, Tebbe et al. [24] reported that gene transfer can occur from orally administered GMMs to various recipients (Arthrobacteria) via transformation in the intestine of springtails (Folsomia candida). Perreten et al. [14] documented the development of a plasmid carrying multiple antibiotic resistances which they had isolated from raw milk cheese. These resistances originated from four different microorganisms and probably developed through the action of antibiotics in the microflora of the lactating cows. The authors take a clear stance on the issue: "To preserve the life-saving potential of antibiotics, the spread of resistance genes at all levels must be stopped. Distribution routes like those between animals, food and consumers have to be interrupted." ([14], p.802). Only recently transformation events in an artificial mammalian gastro-intestinal tract could be detected with a probability of one in 10 million. Given the billions of bacteria inhabiting our intestine that is not really a rare event. [22].
Vertical gene transfer Another central issue that has featured in discussions on the cultivation of transgenic plants since its very beginning is that of outcrossing from such plants and introgression of the recombinant genes to related weed and wild plants. It was more or less accepted, at least in the beginning of the debate, that spread of transgenes should be avoided as best possible, as this may have problematic effects on the composition of wild flora and biocoenoses in general. A further point now attracting increasing attention are the implications of resistance development through outcrossing (e.g. herbicide resistance or insect resistance), as this may not only have consequences for non-cultivated ecosystems but in particular also for agricultural land use systems. The results of hybridisation experiments clearly demonstrate the possibility of a gene flow from rape to wild herb populations. Potential hybridisation partners of Brassica napus are not only to be found in the genus of Brassica but also in other groups of the mustard family [25]. Potential hybridisation partners of rape include in particular wild herbs, which are probably 39
Opportunities and Challenges all subject to a high degree of cross-fertilisation. According to Darmency [26] this crossfertilisation facilitates the transmission of transgenes from rape to associate herbs. Under field conditions rape has proven capable of hybridisation with wild turnip (Brassica rapa), brown mustard (Brassicajuncea), black mustard (Brassica nigra) hoary mustard (Hirschfeldia incana, synonymous with Brassica adpressa), wild radish (Raphanus raphanistrum) and wild mustard (Sinapis arvensis) [27]. All experience and data gained in the course of the past years point to a high probability of rape populations prevailing outside cultivated areas and the possibility of gene flow to nontransgenic populations and related wild herbs. Many of Europe's major crop species have been equipped with identical herbicide resistance genes. Their large-scale use will therefore produce an enormous selective pressure towards corresponding resistant weeds. While rape will be the plant to initiate rapid resistance development, other plants equipped with the same resistance but lacking crossable wild relatives in the region will sustainably promote the onesided selection of weeds rendered resistant by the former. This development will also be accompanied by a further impoverishment in farmland-associated floral species and insects, because of the constantly increasing usage of broad-spectrum herbicides instead of selective herbicides. Furthermore, the cloning of multiple resistances into one and the same crop species also gives related wild herbs the opportunity to acquire multiple resistance. The largescale resistance management schemes now being discussed in anticipation of herbicide resistance problems may have to accommodate whole regions and extend over several rotation periods in order to be effective [28]. That will need a high planning and control effort. No less in conflict with the requirements of sustainability, and with the principles of sustainable utilisation and conservation laid down in the Convention on Biological Diversity, is the endangerment of species diversity entailed in the present herbicide resistance strategies. In the light of the knowledge on horizontal and vertical gene transfer that has accumulated during the past years, the rapid commercialisation of a multitude of herbicide-resistant transgenic plants also constitutes a violation of the precautionary principle. Speakers at international debates are often heard to invoke another principle, namely that decisions should only be made on the basis of scientific knowledge. There is no objection to this, just as long as such knowledge-based decisions really take account of all the relevant scientific evidence available. In concluding I would like to quote Heinemann : "The risk of genetically engineered organisms for commercial preparation is the potential for the engineered product to demonstrate unexpected "monster" qualities or for the genes to escape into the wild fauna and flora and thereby create genetic "monsters". These are risks which cannot be excluded with present data. The potential for escape of a resistance gene introduced into the genome of a commercially desirable plant cannot be gauged by small-scale gene escape experiments. By known examples of gene transfer frequencies in nature, the potential for exchange is too great to be excluded by argument. (...) What we know the least about is the nature of the evolutionary forces that determine the success or failure of monsters. We have limited or no predictive power for the fate of recombinant genes. In the case of an antibiotic resistance, we may be able to say that its known functions pose no additional threats. But we cannot be sure that its known functions are all of its potential functions either on its own or in conjunction with the 40
Public p o l i c y a n d c o n s u m e r concerns m a n y n o v e l g e n o m i c c o n t e x t s in w h i c h it m i g h t be f o u n d s h o u l d it be t r a n s f e r r e d horizontally. Therefore, as a qualitatively different t e c h n o l o g y , genetic e n g i n e e r i n g s h o u l d be c o m m e r c i a l i s e d w i t h e x t r e m e c a u t i o n until the a p p r o p r i a t e scientific e x p e r i m e n t s can be c o n d u c t e d " ([29], p.23).
References 1.
2.
3. 4. 5. 6. 7. 8. 9.
10. 11.
12. 13. 14. 15.
16. 17.
18. 19. 20.
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