Dec 2, 2002

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Soil ecology:

Reversible processes

One project from the accompanying biosafety research into T4 lysozyme potatoes examined the effects on nodule bacteria (rhizobia). In various laboratory tests rhizobia proved to be very sensitive to T4 lysozyme. However, in greenhouse and field trials no adverse effects caused by T4 lysozyme could be found. Project director Dr. Inge Broer concludes that the prevailing conditions on the site such as sunlight have a far greater effect on the bacteria. GMO Safety spoke to her about the risks to soil ecology posed by the deliberate release of transgenic plants.

Fenced-in circles each with an inner ring of transgenic potatoes and an outer ring of non-transgenic potatoes. Vetch has been sown in between so that the potatoes and vetch are very close together.

GMO Safety: You have recently discovered that, in the case of rhizobia, all other influences are much more significant than the influence of lysozyme. Can that be applied in general to all transgenic plants and proteins that may be released into the soil?

Inge Broer: Well, I believe that if I observe a minimal or small effect in the laboratory, then I’ve got no chance of seeing anything in the field. If I observe a dramatic affect in the laboratory, then it must be followed up. The first thing I would do would be to take a flowerpot of sterile soil and see what happens there. If my effect has disappeared, then I don’t need to carry out any expensive field trials.

GMO Safety: You could of course argue this the other way around, i.e. if a problem or a danger is identified in the laboratory, then one shouldn’t even take the risk of testing it in the field.

Inge Broer: Well in that case of course one would have to define what sort of risk it is. If I change bacterial populations in the soil, that is in fact a process which can always be reversed. But just because I change something in the local population does not mean that I will suddenly wipe out a certain species of bacteria. This bacterium will still be present in the marginal areas where my protein doesn’t reach, even if the effect is really dramatic. If this field is ploughed next year and these bacteria are needed or find suitable growing conditions then their numbers will increase again and they will return. So I cannot cause any lasting effects on a field by growing a specific plant. Of course if I apply certain chemicals to a field over several decades then I can certainly cause lasting effects, but not by growing a plant for one year.

GMO Safety: But the critics always argue that we actually understand virtually nothing about soil microecology and can only identify or cultivate a few soil organisms. They claim that whilst our knowledge of soil microecology remains so incomplete, we should not allow contamination with transgenes.

Inge Broer: I simply cannot understand this argument. Of course we don’t understand everything about the soil, but if you follow this line of reasoning, then you’d have to say that I must stop ploughing the soil as well, I must stop growing certain varieties because I’m certainly causing dramatic changes to the population by doing so.

GMO Safety: So if sensitive damage were to be caused to the ecosystem of the soil as a result of whatever affect, whatever technology, one would have to regard that as some kind of consequence?

Inge Broer: Well that would depend on the definition of damage. Changes to the colonisation of the soil happen all the time, for all sorts of reasons; they are normal. In my view a harmful change can only be one that impairs plant growth, for example when pathogens arise or beneficial organisms disappear.

GMO Safety: So what has become of the lysozyme potato?

Inge Broer: I think there are two reasons why there has been no further progress with lysozyme potatoes. First the patent situation, but also perhaps because the effect that was observed, in other words the degree of improvement, was insufficient. It wasn’t big or impressive enough to make me want to market these plants now - under the difficult conditions for licensing transgenic plants. Fighting bacterial infections is extremely difficult. You get success rates of maybe ten to fifteen percent healthier potatoes.Had that been achieved with a conventional breeding strategy, then it wouldn’t have been an issue, they would have been marketed straight away, but this is a transgenic plant.