24 March 2002

"ASSESSING THE IMPACT OF GM PLANTS" - EXTRACTS

1. GM crops bound to 'escape', says EU - Independent On Sunday
2. Extracts selected by the Soil Association from:
"Assessing the Impact of GM Plants" - A review and interpretation of published literature and recent/current research
The European Science Foundation and the European Environment Agency

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1. GM crops bound to 'escape', says EU

http://news.independent.co.uk/world/environment/story.jsp?story=277878
By Geoffrey Lean, Environment Editor
Independent On Sunday
24 March 2002

Genes will inevitably escape from genetically modified crops, contaminating organic farms, creating superweeds, and driving wild plants to extinction, an official EU study concludes.

It adds that the three GM crops at present being trialled in Britain - maize, sugar beet and oilseed rape - pose the greatest risks of all the varieties it examined.

The study, just published by the European Environment Agency, confirms environmentalists' worst fears and will make it very difficult for the Government to approve the commercial planting of GM crops in Britain.

Ministers, who have consistently promised not to permit the crops if they are found to endanger the environment, will have to make a decision next year after the completion of three years of trials. But the trials are primarily designed to examine the use of pesticides on GM crops, not to look for escaping genes.

The study concludes that "gene flow can occur over long distances", and that some varieties of GM crops interbreed with others "at higher frequencies and at greater distances than previously thought".

Pollen from the crops, it concluded, travelled far further than the official "isolation distances" laid down to separate them from ordinary crops, to prevent interbreeding, making a mockery of safety precautions.

Cross-pollination by GM oilseed rape has been recorded about two and a half miles away from the crop, compared to an isolation distance of 600m. Research in Scotland has suggested that bees could carry the pollen at least six miles. The report concludes: "Under current farm practices, local contamination between crops is inevitable."

Environmentalists will see it as a vindication of their view that organic and non-GM crops will not be able to co-exist for long before being contaminated, denying shoppers a choice of food.

The report warns that "over time even small amounts of gene flow can have important effects on evolutionary change". It expects superweeds, resistant to herbicides, to become "common" if GM crops are grown, and warns organic farmers will find it hard to sell their produce once it has been infiltrated by GM genes. And it adds that the interbreeding could lead to natural wild relatives of the crops becoming extinct.

Peter Melchett, the policy director of the Soil Association, said: "The Government and GM industry seem to have picked three of the most contaminating crops to test in the UK. After this report, there should be no question of ministers considering, even for a moment, allowing them to be grown commercially."

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2. Extracts selected by the Soil Association from: "Assessing the Impact of GM Plants" - A review and interpretation of published literature and recent/current research

The European Science Foundation and the European Environment Agency
 

Executive summary

In 2000 the EEA [European Environment Agency] established a special project for the European Parliament, on the dissemination of research results from technologies characterised by scientific complexity and uncertainty, such as GMOs and chemicals, and on the use of such results by the public and their representatives in their governance, including the use of the precautionary principle. This project is in support of the EEA duty, added to its regulation in 1999, to ‘assist the Commission in the diffusion of information on the results of relevant environmental research’. In order to access European scientific expertise and to minimise duplication, the EEA established a partnership with the European Science Foundation to bring together relevant scientific evidence. This is the first report from the project.

This report considers the significance of pollen-mediated gene flow from six major crop types that have been genetically modified and are close to commercial release in the European Union. Oilseed rape, sugar beet, potatoes, maize, wheat and barley are reviewed in detail using recent and current research findings to assess their potential environmental and agronomic impacts. There is also a short review on the current status of GM fruit crops in Europe. Each crop type considered has its own distinctive characteristics of pollen production, dispersal and potential outcrossing, giving varying levels of gene flow.

Oilseed rape can be described as a high-risk crop for crop-to-crop gene flow and from crop to wild relatives. At the farm scale low levels of gene flow will occur at long distances and thus complete genetic isolation will be difficult to maintain. This particularly applies to varieties and lines containing male sterile components, which will outcross with neighbouring fully fertile GM oilseed rape at higher frequencies and at greater distances than traditional varieties. Gene stacking in B. napus has been observed in crops and it is predicted that plants carrying multiple resistance genes will become common post-GM release and consequently GM volunteers may require different herbicide management. Oilseed rape is cross-compatible with a number of wild relatives and thus the likelihood of gene flow to these species is high.

Sugar beet can be described as medium to high risk for gene flow from crop to crop and from crop to wild relatives. Pollen from sugar beet has been recorded at distances of more than 1 km at relatively high frequencies. Cross-pollination in root crops is not usually considered an issue since the crop is harvested before flowering. However a small proportion of plants in a crop will bolt and transgene movement between crops may occur in this way. Hybridisation and introgression between cultivated beet and wild sea beet has been shown to occur.

Maize can be described as a medium to high-risk crop for gene flow from crop to crop. Evidence suggests that GM maize plants would cross-pollinate non-GM maize plants up to and beyond their recommended isolation distance of 200 m. There are no known wild relatives in Europe with which maize can hybridise.

At present none of these crops has pollen which can be completely contained. This means that the movement of seed and pollen will have to be measured and managed much more in the future. Management systems such as spatial and temporal isolation can be used to minimise direct gene flow between crops, and to minimise seed bank and volunteer populations. The use of isolation zones, crop barrier rows and other vegetation barriers between pollen source and recipient crops can reduce pollen dispersal, although changing weather and environmental conditions mean that some long distance pollen dispersal will occur. Biological containment measures are being developed that require research in order to determine whether plant reproduction can be controlled to inhibit gene flow through pollen and/or seed.

The possible implications of hybridisation and introgression between crops and wild plant species are so far unclear because it is difficult to predict how the genetically engineered genes will be expressed in a related wild species. The fitness of wild plant species containing introgressed genes from a GM crop will depend on many factors involving both the genes introgressed and the recipient ecosystem. While it is important to determine frequencies of hybridisation between crops and wild relatives, it is more important to determine whether genes will be introgressed into wild populations and establish at levels which will have a significant ecological impact.
 

Introduction

1.1. Aims and objectives of the report
This report considers the significance of pollen mediated gene flow from six major crop species commonly grown in Europe that have been genetically modified and are close to commercial release in the European Union (EU).

...To conclude the report, future recommendations and considerations are discussed with regard to crop to crop and crop to wild relative gene flow, along with methods of minimising gene flow, such as developing physical and biological barriers.

1.2 Background
Despite the potential benefits of GM crops, there is also concern over the possible environmental and agronomic impacts if the transgenes escape and become established in natural or agricultural ecosystems. From an agronomic point of view, the transfer of novel genes from one crop to another could have a number of implications, including depletions in the quality of conventional and organic crop seed leading to a change in their performance and marketability. Maize, for example, will cross-pollinate with other cultivated maize and sweetcorn (Zea mays ssp. saccharata), directly affecting the quality  and acceptability of the marketed product. Concerns over the ecological impacts of GM crops lie with whether or not a crop has wild relatives and the ability to cross-pollinate them. If crops hybridise with wild relatives and gene introgression occurs wild populations could incorporate transgenes that change their behaviour and they could present an economic threat as weeds or an environmental threat as competitors in natural communities. Oilseed rape, grasses and several fruit crops have varying degrees of sexual compatibility with a number of wild relatives found in Europe, and introgression of novel crop genes into some of these relatives is likely. Other crops, for example maize, have no wild relatives with which they could potentially cross-pollinate in Europe.

1.3. Factors affecting pollen dispersal and cross-pollination...[for example]
1.3.3.1 Weather
Pollen dispersal can be heavily influenced by the weather and changes in temperature, humidity and light, as well as wind and rain. For example, studies on pollen dispersal by Scott (1970) over several years revealed that the average concentration of oilseed rape pollen during one day of one year measured 1.4 % of that on the same day the following year. This was due to heavy rain and high humidity on the first day compared with sunshine and low humidity on that day a year later. Wind strength can also have an important role in distributing pollen grains significant distances within their viability periods.

1.5 Routes of transgene movement between species
...Though the emphasis of this report is on pollen mediated gene flow, it is important to recognise that this comprises of only one element of the movement of genes within and between populations.
 

9. Evaluation and conclusions

9.1. Oilseed rape
...Low frequencies of cross-pollination have been recorded at distances of up to 4 km from the source.

Seed dispersal allows "GM plants (to) persist at sites for several years."

On a farm-scale the current recommended isolation distance of 100 m will maintain cross-pollination levels at below 0.5 % in the majority of fully fertile crops.

Varieties and lines containing male sterile components will outcross with neighbouring fully fertile GM oilseed rape at higher frequencies and at greater distances than was previously thought.

Gene flow will occur to and from volunteer and feral [wild plant] populations which can act as gene pools carrying over the contamination into subsequent rape crops.

Gene stacking in volunteers has been observed in GM crops. It is predicted that plants carrying multiple resistances will become common once GM herbicide tolerant rape is widely commercialised.

...The risk of hybridisation between oilseed rape and some wild relatives, is high. The creation of a herbicide tolerant, competent weed is possible.

Oilseed rape can be described as a high risk crop for pollen mediated gene flow from crop to crop and from crop to wild relatives.

9.2. Sugar beet
Pollen from sugar beet seed crops is primarily wind dispersed and has been recorded at distances of more than 1 km at relatively high frequencies. Appropriate atmospheric conditions combined with peak pollen release times can account for longer distance dispersal. Sugar beet flowers are visited by a range of pollinating insect species.

The current recommended isolation distance for GM beet seed production of 1000m may not guarantee the prevention of seed contamination in the long term.

Seed can survive in soil from one beet crop to another causing contamination of subsequent crops.

A small proportion of plants in a crop will bolt and transgene movement between crops may occur in this way. GM bolters occurring in a following crop of conventional beet may pollinate bolters in the current crop and be taken up with the crop at harvest, causing contamination.
 
...Hybridisation and introgression between cultivated beet and wild sea beet has been shown to occur. GM traits could therefore introgress into wild beets.

Sugar beet can be described as a medium to high risk crop for pollen mediated gene flow from crop to crop (especially seed crops) and from crop to wild relatives.

9.4. Maize
Maize is primarily wind pollinated although there is evidence to suggest that bees and other insects collect pollen from maize. The majority of airborne pollen is shown to fall within a short distance of the pollen source, though outcrossing has been recorded at up to 800m. It is predicted that under suitable atmospheric conditions maize pollen has the potential to travel over much longer distances.

There is no evidence that any current variety is not interfertile with another variety, for example cross-pollination data between maize and sweetcorn exists.

There are no known wild species in Europe with which maize can hybridise.

Maize can be described as a medium to high risk crop for pollen mediated gene flow from crop to crop, but low risk for gene flow to wild species.
 

10. Future considerations and recommendations

10.1. Gene flow: Crop to crop
At farm and regional scale gene flow can occur over long distances and therefore complete genetic purity will be difficult to maintain within the official isolation distances, for crops such as oilseed rape, maize and sugar beet...

10.2. Gene flow: Crop to wild relatives
It has been recognised that over time even small amounts of gene flow can have important effects on evolutionary change (Wright, 1931). Gene flow between crops and their related wild species may have two potentially harmful consequences: the evolution of increased invasiveness and persistence and the increased likelihood of extinction of wild relatives. It is difficult to predict, however, the precise limits of sexual barriers between individual crop types and their related species, or the likelihood of hybrids forming and persisting in agricultural or natural habitats

10.3 Gene Flow Barriers
10.3.2. Physical gene flow barriers
An isolation zone is an area between a GM crop and a nearby non-GM crop that is either de-vegetated (a ‘barren zone’) or planted with a non-insect pollinated crop that would discourage insect pollinators from leaving the GM crop.
In experiments with oilseed rape field trials Morris et al (1994) found that barren zones less than 8m in width actually increased gene exchange above the amount observed at comparable distances in continuous crops of oilseed rape.
The same type of effect has also been encountered in maize trials.
Further research may establish whether or not standard isolation distances could be applied to GM crops.  Research must also consider how wide an isolation zone must be before it deters insects from moving from one crop to another, and whether a valid option would be to discard the first few outer rows of the recipient crop as ‘buffer’ rows

Soil Association  22 March 2002