Knowledge of fungi helps to map risks of genetically modified crops

Eighty per cent of all plants on earth live together with mycorrhizal fungi. These fungi grow from the plants roots into the soil and help the plant to take up nutrients. In general, the plants grow better as a result of this. Conversely the fungus also benefits from the plant, which provides the fungus with sugars – the product of aboveground photosynthesis – that flow from the plant to the rates.

Biologist Erik Verbruggen went in search of the factors in agricultural fields that affect the species composition of the fungi. The aim was to map when a disruption in the natural variation occurs. The outcome should be usable for testing the possible effects of genetically modified crops on fungal diversity and consequently on natural plant growth.

First of all Verbruggen established the species richness of mycorrhizal fungi under various conditions. 'Only if you know the natural variation can you make statements about what deviates from this,' he explains. Research into the diversity mycorrhizal fungi has never previously been performed on such a large scale in the Netherlands. Verbruggen studied 23 organic fields and an equal number of conventional fields with maize or potatoes, two highly prevalent crops in the Netherlands. In total he came across some 40 species of fungi. In organic farming the diversity was 50% higher than in conventional farming. 'That agrees with earlier studies,' says Verbruggen. ‘However, I came across 2 to 12 species of fungi in both types of agricultural fields. This means that the natural variation is quite considerable.'

Verbruggen then investigated which factors determine the fungal diversity. Phosphate and crop rotation were found to be the most important. The lower the phosphate level in the soil the higher the diversity. The rotational cultivation of different crops also ensures a greater diversity in fungi, with grass-clover being the most important stimulus for fungal diversity. Verbruggen discovered that conventional agricultural fields with a low phosphate level and the regular cultivation of grass-clover still have a high diversity in fungi. In both types of agriculture these same factors ensure that one species of fungus does not predominate over the others. Such a predominance could be a sign of a disruption to the natural balance.

This study provides useful reference points for testing the possible effects of genetically modified crops on soil fungi. Verbruggen performed a test with transgenic maize. This crop did not have a strong disruptive effect on the species composition of fungi. In the future, a greater knowledge of fungi could allow more new crop varieties to be tested. Genetically modified crops are not cultivated in the Netherlands for commercial purposes but there are trial fields and laboratories that focus on the development of such crops.

More information: Verbruggen defended his doctoral research into plant fungi on Thursday 9 February 2012.

Provided by Netherlands Organisation for Scientific Research (NWO)