Exceptional customer service Get specialist help and advice. This book reviews the ecological and evolutionary effects of introductory GM cultivars. As a result it represents a major contribution to the debate about the risks of GM crops and measures, required to determine the longer-term impact of GM crops on ecosystems. Newsletter Google 4. Help pages. Prothero Michael J.
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Images Additional images. Muir emphasised that if one is to determine which GM species plant or animal might present a gene flow risk in developing countries, then we have to first consider that gene flow can only occur with species already found in developing countries. For the different agricultural sectors, he summarised thus: "many of the domesticated plants came from developing countries, including, but not limited to: rice, papaya, cassava, eucalypti trees, maize, and tomato. Many domesticated animals have their origin in developing countries but the species of perhaps greatest concern is tilapia, which come to us from Africa.
The world market for tilapia is growing at record pace and GM tilapia have been developed. The concern is what happens if these GM species find their way back to their global centers of origin? For forest trees, Lindgren suggested that in order to avoid gene flow to native species, GM forests with exotic species may be proposed for developing countries. Having assessed the ecological risk of gene flow from a certain GM variety, what then?
Nickson 24 underlined the importance of "comparative risk assessment" i. Wozniak 87 agreed, writing that the ecological risk of GM gene flow to wild relatives needed to be compared "to the impacts already occurring from non-engineered cultivated varieties that hybridize with related species or wild populations". In this comparative context, Muir pointed out that it is easier to determine the ecological risks from GM gene flow than from invasive alien species because the non-GM species already exists in the ecosystem and can act as a control, whereas for an introduced species there is no real control.
Ghislain 35 suggested that any ecological risks from gene flow needed to be put in the context of the environment in which they might be used. He argued that if risk assessment showed that there was a reasonable probability of a certain GM variety posing a threat to biodiversity, then the country would have to develop policies "considering the relevance of these threats for each region.
By relevance, I mean in an area of intensive mining, deforestation or urban pollution, it is irrelevant to care about a remote event of gene flow in balance with all the other threats It was also argued that potential ecological risks from gene flow should be weighed up against potential benefits of applying GM crops.
- Introgression from Genetically Modified Plants into Wild Relatives.
- Transgene introgression from genetically modified crops to their wild relatives..
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It is inconceivable to me that a country in this world does not have people with the scientific and public policy capabilities. As such, I firmly believe that a scientifically based, risk assessment that integrates social aspects is the appropriate tool for decision making anywhere in the world". For developing countries, Lingareddy 99 also weighed up the potential increases in production from applying GMOs against the potential negative ecological consequences, but felt that for their long-term interests it was better to be cautious and not use them.
Jeggo 86 pointed out that many countries have committees and procedures in place to carry out evaluations involving the development, release or use of GMOs in terms of safety and benefits and proposed that, since the risks cannot be limited by national boundaries, an international committee be formed to carry out such evaluations. As seen in the previous section, concerns about the current or potential ecological impact of gene flow from GM to non-GM populations, meant that there was much discussion about how the potential risks might be assessed prior to release.
Potential ecological hazards need first to be identified.
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This may not be straightforward, as it depends on whether GMOs are considered to be fundamentally different from conventionally bred organisms Wuerthele, 1 or whether potential hazards may be identified prior to release Muir, The probability of gene flow exposure needs then to be calculated and, as seen earlier, this can be quite complex and, if population genetics models are to be used, may require expensive testing facilities Muir, In addition, in developing countries, gathering ecological information can be difficult, as funding Morris, 6 and capacity Ashton, 47 may be limited.
An alternative approach is to simply prevent or limit gene flow from GM populations Muir, Gressel 43 pointed out that there are a variety of strategies that would "render gene introgression to other varieties, landraces and wild species nigh impossible" and suggested that "the use of such strategies should be a requirement prior to release when there is a crop at risk".
The large number of different strategies available was highlighted by Choudhary 20 and, by coincidence, the journal "Nature Biotechnology" June , Number 6 , containing a special section on the environmental impacts of GM crops and describing the current status of these strategies, was released while the conference was underway Burke, 17 ; Smyth, As Muir suggested, these strategies could be combined to ensure that gene flow will not take place. A range of different strategies were discussed in the conference:.
According to Nishio 11 , timing reproduction of GM crops to occur at different times from native varieties "does not seem feasible". However, Lindgren suggested that growing GM forest trees with short rotation times so that they can be harvested in their juvenile stage when they typically would have spread little pollen or seeds might be useful for limiting gene flow.
Cummins 97 proposed that cultivation of GM fish could be considered as long as it takes place in inland facilities rather than fish pens, where they could escape and mate with wild relatives. For crops, Muhunthan 2 proposed establishing "GM-free zones around the GM populations to prevent gene flow between GM and non-GM populations", although participants mentioned the problems of defining appropriate isolation distances. Cummins 12 reported that pollen from GM canola had been observed to spread far greater distances in Canada than previously considered.
Di-Giovanni 23 highlighted the difficulties of setting standard isolation distances for GM populations as "pollen- and gene-flow are inherently variable phenomena" potentially influenced by factors such as wind speed, atmospheric stability and turbulence, pollen viability and other biological factors meaning that "it would be unwise to base decisions on a few field trials".
He advocated the use of computer simulation models to assess the probabilities of pollen dispersal for wind pollinated outcrossing plants. Muhunthan 15 argued that because farm sizes are small in developing countries, "there will not be any space left to set up a refuge". A number of different strategies to ensure the GMOs or their pollen are sterile were discussed.
One of them is development of GM plants whose seeds are sterile, using so-called "terminator" technologies e. Nishio, 11 ; Stuart, Valdivia-Granda 40 warned, however, that the strategy represented a risk to subsistence farmers who might be unable to segregate the sterile seed. Gressel 43 proposed that for vegetatively propagated GM crops, a gene causing infertility no pollen could be inserted in a tandem construct with the transgene, so that gene flow would not be an issue.
Introgression from genetically modified plants into wild relatives and its consequences - DTU Orbit
He pointed out that many genes are already known that render pollen infertile. For plant species that produce a lot of pollen e. He proposed that the male sterile varieties could be based on systems of cytoplasmic male sterility. For fish, Cummins 97 considered the proposal to use triploidisation i. He argued, however, that triploidisation might be problematic as the technique could have physiological side effects and, secondly, triploids might be "leaky", allowing some fertile gametes to be produced.
Given the potential risk that release of GM fish might have on the environment, he proposed that spatial separation of GM fish rather than triploidisation should be used and concluded that "extensive studies on sterile triploid leakiness to produce gametes should be done before any transgenic fish are exposed to the environment". For forest trees, Lindgren maintained that use of sterile trees could eliminate or reduce gene flow. He pointed out, however, that to "prove absolute sterility, long field-testing under variable conditions is often needed, and this is expensive, complicated and time consuming".
He suggested that if tree sterility was a requirement then it "is likely to lead to increased use of vegetative propagation with a few well-tested sterile clones". Another strategy mentioned was to insert the transgene s into the chloroplast genome rather the nuclear genome Valdivia-Granda, 40 ; Murphy, As chloroplast genomes are maternally inherited in most crops, dispersal of transgenes through pollen would thus be prevented, although Valdivia-Granda 40 indicated that it would not be effective in all crops. Cummins 52 emphasised that some species might not show clear maternal transmission i.
He concluded that "individual crop plants and weeds need full analysis of the mode of chloroplast transmission before it could be concluded that the transgenic chloroplast modifications eliminate transgene transmission through pollen". This was one of the most divisive topics raised during the conference, resulting from a dichotomy in the way that GMOs are viewed in relation to CBOs.
Interaction with the environment
Nielsen 95 , agreeing with Wuerthele 1 , felt that the essential issue regarding the consequences of gene flow from GMOs was whether transgenic organisms differ fundamentally in their genetic make-up from other traditionally bred organisms, "if the answer to this question is no, then no particular concerns are to be raised that would separate the assessment of GMOs as compared to traditionally bred organisms. If the answer is yes, then the unique features should be identified and the consequences of their dispersal by gene flow evaluated".
Some participants considered that the answer was no and, as a consequence, gene flow from GM-populations is not more of an issue than gene flow from non-GM populations. Thus, Mettler 53 argued that "the identification of one gene as being a transgene for example for disease resistance is no more of a threat [to biodiversity] than the already common use of conventionally developed traits for disease resistance", while Burke 17 questioned why herbicide tolerant canola developed using genetic modification or conventional breeding should be treated differently.
Introgression from genetically modified plants into wild relatives and its consequences
A number of participants e. Bradshaw 5 ; Wozniak, 25 ; Burke, 64 also emphasised that conventional breeding may use technologies with considerable impact on a plant's genetic material i. This includes transfer from species through bridging crosses that bring gene combinations together that would otherwise not occur naturally" Wozniak, 25 , and that GMOs are therefore not fundamentally different from CBOs.
Other participants, instead, felt that GMOs are fundamentally different from CBOs in one or a number of ways and, consequently, there are "novel concerns about their effects on ecosystems at the genetic level and about their behavior in ecosystems at the agricultural level" Wuerthele, 1.
She argued that some of the world's most serious environmental problems came from the failure to identify new hazards raised by new technologies and thus, "if GMOs are fundamentally different, The principal differences between GMOs and CBOs that participants mentioned in the context of potential impacts for gene flow may be roughly subdivided into the following two categories, that are presented here, together with the resulting new hazards they may entail:.