Eight small plots of wheat at Rothamsted research centre are the focus of an increasingly bitter dispute. These 6 metre by 6 metre squares of genetically modified cereals are threatened with destruction by one group of determined environmental campaigners this weekend (27th May 2012). Other equally committed environmentalists fiercely defend the importance of the science. If successful, the Rothmasted GM wheat will reduce the need for the use of insecticides, particularly the group called pyrethroids that kill aphids and other pests as well as beneficial insects. Since pyrethroids may be implicated in the collapse in pollinating bee numbers, GM wheat might have major beneficial impacts.
Wheat is the single most important source of human nutrition. About 20% of the world’s calories come from this crop. Increasing the yield from this cereal is therefore a crucial part of the world’s route towards securing food for three billion more people by 2050. Aphid infestation can cause significant losses to the tonnage of wheat taken from a field. One pest – wheat midge – can reduce yields by 50% or more in the most affected fields. Reducing losses to wheat crops caused by aphids is a vital part of improving global food availability.
The Rothamsted GM wheat incorporates a gene that helps create a substance called (E) beta farnesene. The chemical is what is known as an ‘alarm pheromone’ produced by aphids. It signals danger to other aphids, which therefore tend to avoid it. By contrast, the predators of aphids seem to be attracted to it, perhaps because it identifies where large concentrations of their prey might be found.
( E) beta farnesene is found in several common plants, such as peppermint, and the Rothamsted researchers have added the genes that create this substance to the genome of wheat. (Anyone with mint in the garden knows that it is rarely damaged by insects – so at least in the UK the omens are good). This genetic modification is building on a recent series of papers suggesting that directly applying E beta farnesene to wheat may reduce aphid numbers on the crop. Incorporating the production of farnesene into the wheat itself may be an even better way of reducing aphid damage.
The main benefit from the genetic modification may be the reduction in the need to use synthetic insecticides. In the UK about three quarters of all wheat has an insecticide applied, according to the last government survey. Most of these fields have synthetic pyrethroids sprayed onto the crop. Artificial pyrethoids are similar to the natural insect repellent in plants such as chrysanthemums. These insecticides work by affecting the sodium ‘gates’ in organisms and are particularly destructive to insects and to aquatic animals. These insecticides are only toxic to mammals in extremely high doses and their short life means that they are regarded as relatively safe. But they destroy all insects, including the predators of wheat-destroying aphids and so tend to diminish biodiversity.
There is some evidence that sub-lethal doses of pyrethroids, perhaps in combination with other insecticides such as neonictiniods, affect many higher functions of creatures such as bees. By ‘higher functions’, I mean such things as memory (for example, where the home hive is) and ability to communicate the direction of pollen through the bee dance to other hive residents.
Vital though they are to crop protection, pyrethroids may therefore also cause some of the problems we now see in bee survival. Wheat itself does not require bees for pollination but the doses of insecticides are possibly reducing the number of bees in the wild, with severe consequences for the future pollination of many other crops.
The argument in favour of the Rothamsted GM experiment is that – if successful – it will help to reduce the insecticide load experienced by bees during their foraging. The world needs Rothamsted to succeed if it is to produce more food at a lower environmental cost. Many of the complaints about the experiment, such as the risk of contamination of locally grown wheat, are almost certainly wrong, simply because the E beta farnesene gene introduced into the Rothamsted wheat is extremely unlikely to be able to be transmitted to non-GM crops. In particular, wheat pollen does not travel more than a few metres and even if does merge with non GM wheat almost certainly cannot transmit the E beta farnesene gene.
Rothamsted research centre is probably the oldest plant breeding laboratory in the world. Not only has it assisted in the development of new agricultural technologies, it also claims with much justification to be the ‘birthplace of modern statistical theory and practice’. The new GM wheat trial, properly approved by regulatory authorities, is a worthy and scientifically robust attempt to see if techniques can be developed to reduce the use of chemicals, particularly pyrethroids, in the field. Unfortunately, it is a wonderful irony that the lab that initially developed pyrethroids in the 1960’s was none other than Rothamsted itself. The major improvements in insect control that the laboratory developed to the benefit of people around the world may just have helped trigger part of the collapse of bee populations. Perhaps GM wheat will have the same short term benefits as pyrethroids but then cause further problems in ecological stability.