"There are hopes that resistances can be created using individual targetable genes."
Genetically modified cereal no longer seems to be a topical issue. In 2004 approval applications for herbicide-tolerant GM wheat were withdrawn in the USA and Canada because of fears that exports to Europe would be lost. Deliberate release trials with fungus-resistant wheat in Germany were destroyed twice and finally abandoned. And yet research is still going on. GMO Safety spoke to Karl-Heinz Kogel from the University of Giessen about the key areas of research and the approaches involved.
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GMO Safety: In your view, what is the potential of genetic engineering in cereals? What are the predominant themes and in what area can genetic engineering actually make a substantial contribution to new cereal varieties? Karl-Heinz Kogel: First it has to be said that cereals are ideal plants in terms of biosafety. Wheat and barley in particular are largely self-fertilisers. In most genotypes pollination occurs with closed flowers and the pollen, if it drifts at all, is very rapidly deactivated by sunlight, moisture and climatic influences. In addition barley has no cross-fertilisation partner in Europe with which to produce fertile progeny. From a safety perspective therefore these cereals are particularly suitable for use in biotechnology – alongside normal breeding methods – to obtain improved traits, for example ones which are adapted to the needs of current agricultural production methods, or which confer an ecological advantage. GMO Safety: So what can be achieved using biotechnological or genetic procedures, which is not possible using conventional methods? Karl-Heinz Kogel: Well, in this particular field of resistance of cereals to microbial diseases there are many examples which it is hoped will achieve modern crop production with an even greater long-term reduction in the use of pesticides. Parasitic fungi are a serious problem in cereal cultivation in Europe and the rest of the world, particularly fungi which produce mycotoxins in the ears. We often underestimate the toxicity of these natural products today. Mycotoxins, such as those produced by fusaria fungi for instance, are in fact a major food safety issue. Today there are thresholds for mycotoxins, but they are frequently exceeded. In conventional cultivation we are basically unable to find a solution to the problem, since fungicides don’t work very well and crop rotations are arranged incorrectly for economic reasons. Increased soil preparation would help by working the infectious fungal spores further into the soil. GMO Safety: So increased soil preparation minimises fungal infection? Karl-Heinz Kogel: That is correct, but intensive soil cultivation is generally avoided nowadays, to reduce the risk of soil erosion and to protect the soil ecosystem, and also to reduce costs. The current trend of reducing soil preparation, which is both ecologically and financially driven, results in increased infection with fusaria fungi which in turn creates a food safety problem.It is evident that the complex problem of fusarium toxins is best solved using modern plant breeding methods. In this particular example, where no natural highly effective resistances have yet been identified in cereals, biotechnology is a key technology area. |
GMO Safety: If we could just return to conventional resistance breeding for a moment, there is a whole range of varieties, which, although not actually resistant, have an increased resistance to e.g. fusaria, aren't there?
Karl-Heinz Kogel: Since the general public has become aware of the problem of "fusaria and mycotoxins", classic resistance breeding in this area has improved and increased. Today plants are being bred specifically for fusarium resistance and in some cases this has met with success. But the problem is that fusarium is a necrotrophic i.e. toxin-producing fungus and we have virtually no resistance genes at our disposal to fight these fungi. So breeding success is harder to achieve than with mildew or rust resistance, for example, where one gene is involved, which is hybridised, enabling a high degree of resistance to be obtained within just a few years. Unfortunately this is not the case with fusarium. Here, resistance is based on the interaction of several genes, the so-called quantitative trait loci (QTLs). Several genes are involved in the expression of a single trait. These genes, located at various sites in the genome, are not as easy to manipulate using plant-breeding methods, so it would take decades to achieve a high degree of resistance.
GMO Safety: But when several genes have to be optimised to achieve the desired effect, rather than just inserting the single resistance gene, doesn't that create problems or complications for genetic procedures as well?
Karl-Heinz Kogel: With the genetic method, of course, we have the advantage of being able to cross species boundaries and are not reliant on taking a gene from wheat or barley to obtain fusarium resistance. We can include all possible species in our search for genes which are believed to be effective against fusarium, based on our present understanding of science. There are hopes that resistances can be created using individual targetable genes, which will enable us to tackle the really problematic, even dangerous fusarium disease.
GMO Safety: Do these genes exist?
Karl-Heinz Kogel: Many genes have already been identified, which may eventually be used in agriculture, such as genes which increase the antioxidant status of plants, or genes for enzymes which break down fungal hyphae, such as chitinases or glucanases. We have also found genes which inhibit plant cell death and so interfere with the fusarium's attempts to kill off the plant cells.
There is also a new generation of genes which deactivate the virulence factors of fusarium, which the fungus needs to successfully produce an infection. Furthermore, we now know from microscopic studies where the fusarium toxins are active in the plant: that too would be a biotechnological approach, focussing on toxin breakdown.
GMO Safety: So in other words there are several potential candidates. How far are we from actually producing a transgenic plant which is resistant to fusarium?
Karl-Heinz Kogel: We have genes which show clear effects against fusaria and we and other working groups already have transgenic plants in the laboratory which are effective at combating the fusarium disease. But there are still a few years to go before actually going into agronomic production. In this context it is important for me to stress once more that biotechnology in agriculture is of course only one of several options which could support any type of agricultural production, be it conventional or organic-dynamic. I would also like to stress that we don’t yet have the ultimate proof that biotechnological modifications to cereal can permanently reduce the use of pesticides. But then the role of science is to “predict” developments rather than be steamrollered by them. In this sense I would like our safety research on cereal to be regarded as pre-emptive consumer protection, because whether you like it or not, biotechnology is already seen throughout the world as a new key technology, even in the field of modern agriculture.
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