A slight difference and significant similarities

There is little difference between the composition of the genetically produced potatoes known as fructan potatoes and that of conventionally bred varieties. They only differ in the new substances intentionally incorporated with gene technology. This conclusion has been reached by scientists at the Max Planck Institute of Molecular Plant Physiology and their colleagues from the University of Wales in a study published in the Proceedings of the National Academy of Sciences (PNAS, Online Early Edition, September 19). The scientists used a method developed at the Institute to identify substances in plants.

The researchers compared genetically modified Desiree potatoes, which have a very high level of the polysaccharide inulin, with five conventional varieties. Inulin is a sugar in the class of fructans, i.e. polysaccharides, composed of fructose (fruit sugar). The normal starch is made of glucose. Nutritionally, fructans are classed as fiber and have a beneficial effect on human intestinal flora.

The main results of the study showed that substances in the Agria, Desiree, Granola, Linda and Solara varieties exhibit a surprising range of variation. The genetically modified lines from the Desiree variety lie within the same of range of variation as the five conventional varieties. The exception is the higher content of inulin polysaccharides. There was no evidence of any new, unexpected substances.

Inulin is a polysaccharide that is formed as a storage molecule in many plants such as chicory, artichokes and dandelions. Two different genes for the formation of inulin sugars were introduced into the potato as these polysaccharides have a beneficial effect on human intestinal flora and are therefore a very desirable nutritional component. Potatoes containing inulin were developed at the Max Planck Institute of Molecular Plant Physiology in Potsdam as early as 2000. The properties of these new fructan potatoes were investigated from 2001 to 2004 by the research group Forschungsverbund Fruktan-Kartoffeln, which is financed by the German Federal Ministry for Education and Research. (www.biosicherheit.de/kartoffeln).

Discussions concerning genetically modified foodstuffs repeatedly give rise to misgivings that, along with the desired changes, plants could also contain other new, unwanted substances. However, a comprehensive substance comparison between individual plant varieties is costly, as hundreds of substances have to be measured simultaneously. Former Max Planck research group head Oliver Fiehn, who has been working at the University of California in Davis since the beginning of 2005, developed some ingenious methods to do this during his time in Potsdam. These methods, which are known in technical jargon as metabolomics and are both technically and statistically demanding, have now been applied by Fiehen together with colleagues from the University of Wales to the potato varieties listed above. "Our methods can of course be adapted for comparing other food plants," says Fiehn.

The analyses were financed by the British Food Standards Agency. All in all, almost 2,800 potato specimens, cultivated in trial fields at the German Federal Agency for Agriculture and Food, were tested. A team of biologists, chemists and computer scientists from Potsdam and Aberystwyth in Wales took part in the evaluation.

Source : Max-Planck-Gesellschaft