Jan 28, 2011

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Genetically modified trees

“In the discussion about genetically modified trees also the advantages should be considered”

Genetically modified (GM) trees are being developed since 1986. Over 700 release trials have taken place. But how safe are transgenic trees? What are the findings to date? GMO Safety spoke to Matthias Fladung of the Johann-Heinrich von Thünen Institute (vTI).

The GM trees that have been developed so far contain new traits, like cold tolerance, insect resistance, virus resistance or modified wood characteristics, e.g. a lower lignin content. The GM trees are intended to make the production of renewable raw materials and biofuels more efficient and more environmentally friendly. However, there is increasing opposition to the release of GM trees. At the UN conferences on biological safety (COP MOP) there were calls for tougher regulations for release trials. The German Society for Nature Conservation (NABU) has described the long-term consequences of growing GM trees as unforeseeable for nature and the environment and refers to a study published by the Testbiotech association in December 2010.

GMO Safety: Opponents of genetic engineering describe the deliberate release of transgenic trees as an incalculable ecological risk. What negative ecological impacts have been scientifically proven for transgenic trees so far?

Matthias Fladung: Genetically modified trees have been tested in the field for more than twenty years. So far, no scientific evidence has been found for any specific environmental risks associated with GM trees. There are no indications that GM trees have a negative impact on species diversity or human health. Neither are there any indications so far of horizontal transfer of the inserted genes to soil fungi. The new genes in the trees remained stable in all tests and no unexpected effects of the genetic modification were found. This is the result of our evaluation, published last year in Nature Biotechnology, of the publicly available global evidence on this topic. Even critical studies, like the Testbiotech paper published last December, come to the conclusion that there is no scientific evidence of negative impacts. The risks it describes are entirely postulated and have no scientific basis.

GMO Safety: Is there not a justifiable cause for concerns if GM trees were to spread uncontrollably? Unlike crop plants like maize or oilseed rape, trees are particularly long-lived organisms. And, unlike a field, the forest is a particularly complex ecosystem that must be protected.

Matthias Fladung: You are quite right there. It is our view at present that a spread of GM trees in forests must be prevented. There is a clear consensus on this among all the scientists involved. And this is also the aim of our biosafety research into GM trees, which is based on the precautionary principle. No GM tree should be allowed into circulation without a comprehensive risk assessment.

GMO Safety: But in China more than a million GM trees have been planted. Isn’t that a contradiction?

Matthias Fladung: The situation in China is a special one. They were going for rapid reforestation with fast-growing poplars. The poplars are intended to act as a protective shield to prevent the increasing spread of the deserts. Insect pests have caused severe damage to China’s native poplars. Reforestation only worked when they used insect-resistant Bt poplars. According to the information we have, they planted sterile GM trees. So far there is no evidence that these trees are spreading outside the areas they were planted in. Something that must be criticised, however, is the fact that there may have been uncontrolled releases in China at the beginning. However, the safety requirements in China have been tightened since then.

GMO Safety: Insect-resistant GM trees could have a fitness advantage over conventional trees and crowd them out if they were allowed to spread uncontrollably. How do researchers deal with such risk scenarios for GM trees in practice?

Matthias Fladung: Growing GM trees on plantations away from forests is one possibility here. There are also various containment systems that can be used to prevent these trees spreading in forests.

GMO Safety: What do such containment systems involve?

Matthias Fladung: Plantation agriculture in itself is already a form of containment. The trees grow in isolation there for five to seven years until they are cut down. It is easy to prevent the trees from spreading via root suckers, e.g. by digging trenches around the plantation and carrying out regular checks. In any case, the spread of trees via root suckers is a very slow process and therefore easy to control. There are other options for preventing trees from spreading via pollen and seeds. You can use sterile trees produced by crossing different genotypes of the same species. Another option is to plant only female trees that do not produce pollen.

GMO Safety: You are also working on the development of sterile trees produced using genetic methods. What is the advantage of this approach?

Matthias Fladung: Sterile trees can be produced faster using genetic methods. With trees in particular, conventional breeding methods are very time-consuming. We can achieve a wide range of objectives using genetic engineering methods. For instance, we can delay the first flowering date significantly. If these trees were grown on plantations, they would no longer flower before being cut down. It also makes the trees more productive and they produce more biomass in the form of wood. This is because trees normally invest a large amount of energy in developing flowers and seeds. In one of our own projects we are pursuing another goal: genetically modified trees that produce pollen which no longer contains the genetic modification. These trees excise the new gene from their genome automatically when producing pollen. This gives us an effective containment system and also means that the trees flower normally. Animals that rely on pollen and nectar from trees will continue to find a source of food in tree plantations of this kind.

GMO Safety: People warn against GM trees saying that they could be genetically unstable and cause unexpected effects. In the Testbiotech study, for instance, they refer to field trials that you conducted with poplars in Germany at the end of the 1990s. They claim that the trees started flowering much earlier than expected under field conditions.

Matthias Fladung: These self-proclaimed experts would do better to find out the true facts. I am astonished that they choose this trial to back up their claim of unexpected effects in GM trees. We were investigating whether a new gene remained stable over a long period of time and under environmental conditions. It was already known that the new gene could alter the flowering time of potatoes. That is why we pointed out the fact in our application for the poplar release trial. The change in flowering time was not an unexpected event. In addition, we found that the new gene showed no signs of instability. During the five-year field trial, the gene and its trait remained stable. Today we still have these plants growing in vitro and the new gene is still stable 17 years later.

GMO Safety: In your view, what are the benefits of growing GM trees?

Matthias Fladung: There should be two sides to the discussions about whether to say yes or no to growing GM trees. The potential risks need to be evaluated scientifically and on a case-by-case basis. But the advantages of GM trees should also be considered. Genetically modified trees can help meet the growing need for renewable raw materials and fuels. Even for trees, productivity needs to be not just maintained, but increased. Because trees have a much higher energy conversion rate than e.g. maize or wheat crops, GM tree plantations could be used very efficiently for the ecologically justifiable production of renewable raw materials and bioethanol. And we should not forget that climate change, which has already begun, could pose problems for forests, which will raise questions about the secure supply of wood in future. At the end of the day, taking a long-term view, the establishment of GM tree plantations everywhere could take some of the immense pressure off tropical rainforests.

GMO Safety: Field trials are regarded very critically by some environmental organisations. Are there alternatives?

Matthias Fladung: My comments clearly show that the safe use of GM trees makes very good ecological sense and therefore contributes towards nature conservation. That ought to please the environmental organisations. Release trials are unavoidable for risk assessments of GM trees. Earlier research has shown that greenhouse results cannot necessarily be transferred to the field. As I have mentioned, small-scale release trials have not found any negative environmental impacts. The only way for us to find out more about ecological interactions is by releasing GM trees on larger areas and studying them. In my view, there is no alternative means of obtaining this knowledge within biosafety research.

GMO Safety: Thank you for talking to us.