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Field trials for the assessment of bio hazards in transgenic wheat in natural conditions

Interview with Dr. Christof Sautter, Institute of Plant Science, ETH Zürich

Mr.Sautter, You wish to test genetically modified wheat which possesses an increased fungal resistance in open field conditions. This type of approach is not unfamiliar in the field of genetic engineering. How does your approach differ from previous studies?

We hope to be able to develop a system which specifically targets particular diseases without side effects for non-target organisms. The fungal diseases which our system is designed to target specifically are the smut and bunt diseases (ustilaginales). The stinking smut is relatively easy to work with and is therefore the subject of our first trials.

What is stinking smut?

Stinking smut is a fungal disease in wheat. The spores infect the wheat at germination. The fungus grows through the stem into the ears and produces spores in the grain. The plant shows no visible signs of disease. Infected wheat grains contain millions of brownish black fungal spores instead of white starch.

What is the significance of this fungus for wheat cultivation?

Stinking smut is highly infectious. A few infected ears of wheat suffice to infect the entire harvest with fungal spores. Hence a low level of infection can result in losses of up to 50 per cent of the harvest in a few growing cycles in the event of a portion of the harvest being reused as seed. In Switzerland five stinking smut ears of wheat in 150 m2 of cultivated ground suffice to disqualify the entire harvest for use as seed. In particular subsistence farmers in developing countries who necessarily re-use a percentage of their harvest as seed face the risk of severe harvest losses through ‚seed transmitted' diseases such as stinking smut.

How successful are the preventative methods (organic farming/conventional farming) employed to date and what are the problems encountered?

Staining with chemical fungicides in conventional and IP (integrated production) farming prevents the outbreak of stinking smut completely. Ground yellow mustard seed provides a reliable method of treatment in an organic farming context but is not completely effective.
Furthermore ground yellow mustard seed is approved only in the case of stinking smut. Warm water treatment in organic farming is difficult and not as effective. Rock powder does not provide sufficient protection. Since these treatment methods are not specific they also effect useful fungi e.g. the mykorrhiza fungi which live in symbiosis with the roots.
We wish to examine the biological safety of these plants and to study in detail the reaction of the prototypes infected with stinking smut in open conditions.
We do not propose their use in agriculture in the near future.

Why is it necessary to follow up the trials under closed conditions in the greenhouse with trials in open conditions?

The greenhouse in effect provides a protected environment. The plants react differently when exposed to wind, rain and to other carriers of disease. Thus closed greenhouse conditions actually favoured the growth of the fungus while the vegetation hall completely prevented infection with the fungus even in the non transgenic controls.
Therefore field conditions cannot be replicated by any means at our disposal.

Which non-target organisms could possibly be effected?

We hope that our system will target the smut and bunt fungi specifically. All smut and bunt fungi pose a disease risk for plants. We will also study the system as it interacts with microbes and insects.
Non-target organisms also include various ground bacteria, other useful fungi (mykorrhiza) as well as a type of flea, flea beetle, springtail, lice and cereal leaf beetle.
To date we have been unable to establish a difference between transgenic and non transgenic controls.
Insofar as we can judge these plants do not therefore pose an ecological risk.

How do you intend to prevent the spread of genetically modified material in the course of this study?

From a purely scientific point of view we can assume that genetic material will not be released from the transgenic plants since wheat is strictly self-pollinating.
However in view of the public's reservations on this issue we intend to cover the transgenic plants with small pollen-proof tents to prevent the escape of pollen in the flowering period.

To which plants could the transgenic wheat conceivably transfer its genetic information?

The transgenic wheat could transfer its genetic information to other wheat plants within a radius of two metres of the plant. In Switzerland this could occur likewise with rye and a number of wild grasses. The resulting plants are however not necessarily capable of survival. Due to the seed wheat's hexaploid set of chromosomes it is almost impossible that the transfer of genetic information to normal diploid wild plants would produce plants capable of survival. The trial area is however located at a considerable distance from other wheat or rye fields and will also be protected with a pollen-proof cover during flowering.

What additional genetic markers were introduced to the wheat along with the virus gene and what risk do they pose?

As is common in research the transgenic wheat plants are prototypes. As well as the KP gene which is of interest to us the plants also contain two markers for technical reasons. These genes would be removed in the case of subsequent agricultural use. The bar-gene is responsible for herbicide tolerance. Herbicide tolerance was the only gene which allowed effective selection in the production of the transgenic wheat lines. However the gene would not be suited for widespread agricultural application on account of the alteration in fruit.. It does not however pose any danger. The plants also contain a gene for ampicillin resistance. When work began on this project many years ago it was impossible to predict the interest which this gene would arouse so many years later. This gene would also be removed in the event of the plants being used in agriculture.

Ampicillin is an antibiotic which is used in cultivating the bacteria on which the transgene is produced before it is transferred to the plants. This gives rise to the general public's fear that a ground bacterium could acquire the ampicillin-resistant gene from the plant and subsequently transfer it horizontally to a bacterium which poses a risk for humans. This bacterium could then no longer be treated with this particular antibiotic which is of course undesirable. The bacterium could however be treated with a different antibiotic. Since these ampicillin-resistant genes originate in ground bacteria and a single gramme of earth taken from arable land can contain circa 10,000 ampicillin-resistant bacteria the particular risks posed by a highly improbable gene transfer from a transgenic plant to a bacterium are negligible and have as yet not been proven to occur in nature. As far as can be determined those antibiotic-resistant bacteria which unfortunately do exist arose as a result of inappropriate medical usage of antibiotics. To put the issue in perspective I should mention that one gramme of cow dung contains circa one million antibiotic resistant bacteria from the intestine. The EU recently approved the usage of antibiotic resistant genes in agriculture and in research experiments until 2003 and 2008 respectively. In the case of subsequent usage in agriculture these marker genes in particular those governing ampicillin resistance would in any case be removed.
You are of the opinion that antibiotic resistance doesn't represent any risk. Why then does the EU intend to prohibit their use from 2008 at the latest?

In my opinion the use of antibiotic resistance in prototypes in the context of small, strictly supervised experiments poses no additional risk. This type of decision always represents a political compromise between the various parties involved . These parties represent differing interests which naturally are coloured by ideological differences. Therefore such decisions do not so much reflect scientifically based concerns as the power relations in the various decision making bodies. Such decisions do not therefore necessarily imply an actual risk as the public may imagine. As the lifting of what was to all intents and purposes a moratorium by the EU demonstrates these decisions are subject to change.

When will the experiments begin and how long will they last?

Our application must first be processed. It is not possible to predict in advance whether it will then be approved. Even in the event of approval planting could not be commenced this season. The experiment is scheduled to last for one growing season only, i.e. from March to July. In the following year the area will be cultivated. However a second planting of transgenic wheat is not envisaged.