Gene flow from GM to non-GM populations in the crop, forestry, animal and fishery sectors
The theme of this conference is the potential importance and impact of gene flow from genetically modified (GM) crops, forest trees, fish or animals to non-GM populations, with particular focus on developing countries. This issue has been raised on numerous occasions by participants in previous e-mail conferences hosted by this FAO Forum (see the report on the first six conferences). The issue of the potential importance and consequence of transgenes moving from GM crops to traditional landraces has also been brought sharply to the forefront recently, following reports of transgenic material in maize landraces cultivated in Oaxaca in southern Mexico, part of the centre of origin and diversification of this crop.
The FAO Electronic Forum on Biotechnology in Food and Agriculture was established in March 2000 to provide a neutral platform for various parties to exchange views and experiences so that it might be possible to better understand and clarify the issues and concerns behind the debate on agricultural biotechnology for developing countries. A conference on the subject of gene flow from GM to non-GM populations appears therefore to be both appropriate and timely.
The issue of gene flow from GM populations is not only of potential relevance to crop landraces or traditional varieties but also to wild relatives of the domesticated species, organic crops or non-GM crops cultivated under intensive conditions. Furthermore, the issue does not only concern crop plants. The current media focus on gene flow in crops is determined primarily by the fact that there is no commercial-scale planting of GM trees and no GM animals or fish are currently approved for human consumption. If (or when) this situation changes, there will also be much focus on gene flow issues in these sectors and therefore they are included here.
The aim of this document is to provide some brief background to the subject as well as to mention some of the factors that should be considered in the conference.
2. Some background on GMOs
A genetically modified organism (GMO) is an organism that has been transformed by the insertion of one or more genes (called transgenes), usually from a different species. For example, two genes from the daffodil Narcissus pseudonarcissus and one gene from the bacteria Erwinia uredovora were inserted into the genetic material of rice to produce the transgenic rice variety commonly known as "Golden Rice", which produces provitamin A.
Different types of genetic modification can be distinguished, depending on the source of the genetic material inserted. Mark Tester in the journal "Nature" of 9 December 1999 (volume 402, page 575) suggested that three classes could be considered
i) Wide transfer: Where genes are transferred from one kingdom to another (e.g. from a bacterium to a plant)
ii) Close transfer: Where genes are transferred from one species to another within the same kingdom (e.g. from one plant species to another)
(iii) Tweaking: Where a gene already present in a species is modified to alter its level or pattern of expression
Active research into genetic modification of living organisms has been ongoing since the 1980's. However, large-scale production of GMOs in agriculture has only taken off in the last few years, with the commercial planting of GM crops. Here, we will briefly look at the current status of GMOs in the crop, forestry, animal and fishery sectors. Note, GM plants and animals being developed to produce human pharmaceuticals (e.g. potatoes containing cholera vaccines or sheep producing proteins for treatment of cystic fibrosis) are not of primary interest in this conference and so are not mentioned below.
a) GM crops
It has been estimated that the global area cultivated with transgenic crops increased from 1.7 to 52.6 million hectares from 1996 to 2001 respectively (ISAAA, 2001). From the 2001 estimates, it can be seen that virtually all transgenic crops were grown in just four countries, the United States, Argentina, Canada and China, responsible for 68, 22, 6 and 3 percent of the cultivated area respectively. Four crops were responsible for virtually all the area cultivated with transgenic varieties, namely soybean (63%), maize (19%), cotton (13%) and canola (5%). Of the 52.6 million hectares, 40.6 million (i.e. 77%) were planted with crops modified for herbicide tolerance; 7.8 million hectares (15%) were modified to include one of the toxin-producing genes from the soil bacterium, Bacillus thuringiensis, to confer insect resistance, while 4.2 million hectares (8%) were planted with crops having both herbicide tolerance and insect resistance.
In addition, several thousand field trials of GM crops have been carried out, involving a wide range of species. In the United States, the majority of trials have been on maize, potatoes and soybeans while in the European Union most have been on maize, sugar beet and canola.
b) GM forest trees
There is no reported commercial-scale production of GM forest trees. However, as the title of a recent article (1 March 2002, volume 295, pages 1626-1629) in the journal "Science" confirms ("Forest biotech edges out of lab"), there is much active research in the area of genetic modification of trees and much technical interest in bringing the GM products past the research stage. The first reported trials with GM trees go back to the 1980's. A 1999 study, commissioned by the World Wildlife Fund (WWF)-UK and WWF International, indicated that more than 100 reported trials had been carried out since 1988, involving at least 24 tree species, and that the majority of the trials had been carried out in the United States and Canada. The recent article in Science reported that the United States Department of Agriculture had received applications to field-test 138 types of GM trees, 52 of them in the last two years. The traits of interest for GM forest research include herbicide tolerance and pest resistance (as for crops), but also a range of other features, such as delayed flowering (so that trees can be harvested before they pollinate) or lowered amounts of lignin (to reduce the costs and environmental pollution associated with paper-making). A review of the developments of new biotechnologies, including genetic modification, in forestry was carried out recently for FAO and some additional information can be found here. All studies point out the difficult decisions facing the forest industry (and particularly the pulp and paper companies) regarding the adoption of GM tree technologies.
c) GM animals
Although transgenic animals (especially mice) are used routinely for research purposes, no GM animals are commercially produced for food purposes. Regulatory approval for GM food animals (excluding fish, that are covered below), has only been sought in a single case - for a GM pig in Australia containing a growth hormone transgene allowing the animals to produce meat more efficiently, which never made it to the market. The kinds of transgenes currently being studied for potential use in commercial populations include the growth hormone gene (to increase growth rates), the phytase gene from bacteria (to reduce phosphorous emissions from pigs) or keratin genes (to improve the properties of wool in sheep).
d) GM fish
Commercial-scale farming of fish is a relatively recent phenomenon compared with crop or livestock production, as is the application of conventional genetic selection programmes to most fish populations. Nevertheless, there is much research and commercial interest in the production of GM fish. The trait of major interest is increased growth rate and transgenic fish from about 20 species, including carp, catfish, salmon and tilapia, have been produced with a growth hormone transgene, for experimental purposes. Two transgenic fish species are awaiting regulatory approval for food purposes - a GM salmon in the United States and a GM tilapia in Cuba; decisions on approval are still pending. The GM salmon is the AquAdvantage Atlantic salmon which contains the Chinook salmon growth hormone gene together with a promoter from the ocean pout's antifreeze gene, allowing the salmon to continue to grow well in winter when, in non-GM salmon, growth would slow down. The GM tilapia is a hybrid containing a modified tilapia growth hormone gene to improve growth and conversion efficiency.
3. Gene flow from GM to non-GM populations
For plants, gene flow may occur in nature by pollen spreading from one population to another. The pollen may be spread in a variety of ways, e.g. by wind, water or animals. Genes from the resulting offspring can be spread further by pollen or by seeds. The minimum requirements for GM gene flow to occur are thus the presence of a sexually-compatible non-GM population in close proximity to the GM population, the possibility of outcrossing between the two populations and the production of fertile hybrids. The degree of outcrossing varies between species e.g. maize and millet are typically cross-pollinated while rice, wheat and barley are primarily self-pollinated. Note that gene flow refers to the exchange of genes among populations and not simply to the dispersal of pollen or seeds. For animals or fish, transgene flow could occur by transgenic individuals mating with non-GM partners and the subsequent production of fertile offspring.
Gene flow may also be facilitated unknowingly by human intervention. For example, for GM crops, this may occur through aid or relief agencies accidentally providing GM seeds in programmes to replenish a ravaged country or region's seed stocks or through farmers using transgenic material, intended as food aid, as seeding stock. In some other situations, GM crop material may be illegally introduced by farmers to non-GM populations because they see an economic advantage in using them.
If gene flow has first occurred, the transgenic material may subsequently spread within the formerly GM-free population or be lost from the population in later generations. A range of factors may influence this outcome, such as the size of the non-GM population, the amount of crossing between the GM and non-GM populations and the number and viability of the resulting seeds or offspring. Another important factor is whether the transgene involved confers a selective advantage. If it does, for example by increasing survival or reproduction, it is likely to spread more rapidly through the population. Conversely, if it has a detrimental impact on the fitness of individuals, the rate of gene flow is likely to be reduced and the transgene may eventually be lost.
In this conference, we wish to consider the issue of gene flow from GM crops, forest trees, animals or fish to non-GM populations, with a special focus on developing countries. What kind of "non-GM populations" are we referring to ? We might crudely categorise them into three classes of populations:
a) wild or feral relatives of domesticated species
b) landraces or "traditional" populations
c) "modern" or "improved" populations.
Here, we will briefly consider some aspects concerning gene flow to these three populations.
a) Wild or feral relatives
About 10,000 years ago, our ancestors began domesticating wild animals and plants, and eating the livestock and crops they produced. The centres of origin for most individual species of domesticated animals and plants are well established. For example, the potato, cassava, llama and guinea pig were all domesticated in the Andes and Amazonia region. Most centres of origin are in developing countries. The cultivation of any GM crop, for example, in its centre of origin has been viewed with concern because of the genetic importance of the wild ancestors of domesticated crops and the wish to protect the biological diversity that these wild relatives represent.
Crossing of domesticated populations with their wild relatives has been well documented in certain crop, forest tree, animal and fish species. For example, in crops, gene flow has been observed between rice and perennial rice, between maize and teosinte and between sugar beet and wild beet while in animals, there is evidence for crossing of domestic cattle with wild North American bison and of domestic pigs with European wild boars.
Potential gene flow from intensively bred forest trees to wild relatives is considered a serious issue by forestry scientists, because of the extensive gene flow possible from trees (e.g. due to their longevity) and their relatively recent domestication history (apart from fruit trees and other crop trees). This point, however, is not specific to GMOs. Introduction of new forest tree populations, varieties or genotypes in areas where local populations are present, and the undocumented movement of forest tree germplasm, represent a major risk of "genetic pollution" in forestry. These risks have been limited, in many cases, by establishing provenance tests (to assess geographic variability in performance) and trials outside of the natural distribution area of native populations, although there are also examples where native populations of species have been brought to the verge of extinction due to gene flow and hybridisation (e.g. the poplar Populus nigra).
For fish, crossing of escaped farmed Atlantic salmon with wild Atlantic salmon is a much-discussed problem and it is also noteworthy that the potential ecological risk of releasing GM fish was the dominant theme raised by participants in the Forum conference held in Summer 2000 devoted to the fishery sector. Gene flow involving alien (introduced) species is a real issue in the fishery sector, where their hybridisation with wild relatives or with farmed fish is well documented.
In this first class of non-GM populations, we could also include feral populations i.e. those that were formerly domesticated but are now growing or living independently of humans.
Landraces, or traditional varieties and breeds, are populations that are the product of breeding or selection carried out by farmers, either deliberately or not, continuously over many generations. They tend to contain high levels of genetic diversity and to be adapted to specific environments, being especially important in environmentally marginal areas. Developing countries typically rely on landraces for much of their production. They are important genetic resources, representing an insurance policy against uncertain markets and environmental conditions for food and agriculture in the future. There are concerns that gene flow from GM populations might negatively affect these valuable genetic resources.
Landraces, like the wild relatives of domesticated species, are not static or genetically frozen in time. They evolve and genetically change from one generation to the next as a result of environmental pressures and selection by the farmers. In addition, gene flow between different landraces, between landraces and improved populations and, particularly in centres of origin, between landraces and wild relatives are documented phenomena for crop and livestock species.
c) "Modern" or "improved" populations
Modern populations, or improved varieties and breeds, may be defined as the products of breeding in the formal system (sometimes called "scientific breeding") by professional breeders working in publicly-funded research institutes or private companies. Compared to traditional agriculture, modern agriculture tends to rely on higher inputs [of water, fertilisers and pesticides for crops and of feeds and veterinary services for animals] and to focus on fewer species and on a smaller number of high-yielding varieties that have less genetic diversity.
Although modern farmers and foresters might be able to afford use of GM technologies, they might decide not to do so for a variety of reasons, e.g. trade (if exporting to a country not accepting GM products), economics (if they consider that the extra cost of GM material outweighs the potential economic advantage) or personal choice. These considerations are also relevant at the industry level. What are the consequences for farmers of gene flow from GM stocks to these non-GM populations ?
In this context, we might also consider populations within organic agriculture, a system that relies on ecosystem management rather than external agricultural inputs and where the use of GMOs is not permitted during any stage of food production, processing or handling. Gene flow from GM populations to organic populations might jeopardise the GM-free status of organic products and potentially impact on the organic certification of individual farmers.
4. Certain factors to be considered in the discussion
This conference considers one particular aspect of the whole agricultural biotechnology debate i.e. gene flow from GM to non-GM populations, focusing on developing countries. Throughout the conference, there are certain items that we would like to see discussed. These are:
- How frequently and at what rate may gene flow occur from GM to non-GM populations. For the crop sector (where an estimated 53 million hectares of GM crops were cultivated in 2001), how frequently is gene flow from GM to non-GM populations currently taking place ?
- The possibilities for detecting gene flow from GM to non-GM populations.
- The potential socio-economical or environmental impacts of gene flow from GM to non-GM populations in developing countries.
- Whether the potential consequences differ in the crop, forestry, animal or fishery sectors.
- Whether the potential consequences differ between particular regions of the developing world.
- Whether the potential consequences are greater for wild relatives, landraces or improved populations.
- Who should be liable for any negative consequences of undesired gene flow.
- Whether gene flow from GM populations is different, or has a greater potential impact, than gene flow from certain kinds of non-GM populations, such as alien (introduced) species or modern populations selected for similar characteristics as GM populations (such as increased growth rates or disease resistance).
- Whether the potential impacts of gene flow from GM populations producing human pharmaceuticals (such as human vaccines from bananas or human interferons from hens) are different than from GM populations modified for agricultural traits.
- Whether the nature of the genetic modification (i.e. wide transfer, close transfer or tweaking - see Section 2) should be considered when evaluating the potential impacts of gene flow from GM populations.
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