Science - November 18, 2009

Case for transgenic plants

Put genetic modification to work for integrated plant protection. Equip plants with Bt genes and extra scents to keep particular insects off them. Then you can cut down on harmful pesticides. So say Wageningen entomologists in this month's Trends in Biotechnology.

'We see a potential role for transgenic plants in a package including the plant protection methods currently used in integrated plant protection', says entomologist Martine Kos, who wrote the article together with Professors Marcel Dicke and Louise Vet. 'You can be very precise with transgenic plants, so that only certain species of caterpillar are targeted. This can replace broad spectrum pesticides in agriculture and horticulture, as these kill useful insects along with the target organisms.'
The literature shows that building insect resistance into plants has its advantages. There is experience with cultivating Bt maize in the US. A gene from the bacillus thuringiensis (Bt) bacteria is built into the genome of the maize plant, so that certain caterpillars that eat the plant are killed. The Bt gene is also built into rice and cotton. The protein product of the Bt gene targets a particular order of insects, either butterflies and moths, or beetles, or flies and mosquitoes. You can modify variants of the Bt genes to obtain an even more specific effect.
'Bt crops have already been cultivated on a large scale in the US and China. No negative effects on environment or health have been shown', says Kos. Because you use less pesticide, you get more useful insects and biodiversity, which can help with organic pest control in the field.
Kos has high expectations, too, of modifying plants to attract the enemies of harmful insects. 'You make the plants manufacture extra scents. That is a very new development. I have just read a recent article about an initial field study of such a plant. German researchers added a gene to maize to attract the enemies of a harmful beetle. And the number of harmful beetles went down by sixty percent. That definitely has potential.'
What is crucial, Kos continues, is that the transgenic plants are safe for other organisms, such as natural enemies, and for human consumption. Her project is part of the ERGO research programme for establishing guidelines for testing that safety. 'We are now using the model plant Arabidopsis to find out how to identify negative effects. What sorts of tests and which insects do you need to measure the effects of transgenes?' NWO is financing the programme, commissioned by four ministries.
Kos knows there is resistance in the Netherlands and neighbouring countries against developing transgenic plants. 'But their cultivation in the world is fast increasing, especially in the US, Latin America and China. And they are already being grown on a small scale in seven European countries. 'We can't hold back the development of transgenic plants any longer.  In which case, it would be better to explore the possibilities so as to prevent negative side-effects. If you integrate it sensibly with existing methods of plant protection, you can produce more food with less poison.'