Crops always have ecological effects. That’s why you should weigh up the effect of genetically modified plants against the influence of several common crops. Even now a GMO is still compared primarily with the same plant without the transgene.
This recommendation has been made by three Wageningen doctoral students. The Wageningen research focused on GMOs with resistance to pest insects. In the cases studied, the ecological effects of the GMOs were no greater than those of the natural variety of common crops. 'But sometimes the effects of GMOs are greater,' says Marcel Dicke, the leader of the research programme. 'It depends on the characteristic that has been built in.'
Doctoral student Benyamin Houshyani made a couple of transgenic plants. One of them produced an odorous substance that attracted the natural enemy of the red spider mite, the predatory mite. He also incorporated genes that increased the production of glucosinolates, natural antibodies against caterpillars. His colleagues Martine Kos and Patrick Kabouw assessed the ecological effects of these plants on other insects, such as ichneumon wasps and predatory enemies, and on soil life. The research used the model plant Arabidopsis. The data translate well to other plants, such as cabbage varieties.
The researchers are advising COGEM, the Dutch committee on genetic modification, how it can best assess the ecological effects of GMOs. As yet, GMOs are still being compared with one variety of the common crop that doesn't have the introduced gene, says Dicke. But that is not a good method. 'The farmer can choose from several varieties, each of which has a slightly different ecological effect. You have to take account of that variety and establish the band width of the effects of the common cultivated varieties. Then you look at whether the effect of a GMO lies within the band width.'
Companies applying to COGEM for a licence don't need to randomly investigate the effect of GMOs on all sorts of organisms in nature, says Dicke, instead they must focus primarily on organisms of ecological and economic importance and that really are being exposed to the products of the transgene. 'Thanks to that random approach, the effect of Bt corn on water fleas was once studied. That isn't useful. You need to carefully select a limited number of organisms.' Moreover, research has shown that greenhouse or lab experiments are often a good predictor of the effects in the field. An ecological test costs breeding stations additional time and money, but testing could be done more effectively, believes Dicke.
Benyamin Houshyani and Martine Kos received their PhDs on 16 March under the supervision of Harro Bouwmeester, Professor of Plant Physiology, and Marcel Dicke, Professor of Entomology, respectively. Patrick Kabouw received his PhD on 1 February under the supervision of Wim van der Putten, Professor of Nematology.