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Posted: July, 2015

Pheromone-Producing GM Wheat Does Not Repel Pests in Field Trials

The pheromone (E)-β-farnesene is known to repel pest aphids from plants that they would otherwise feed on. It also attracts natural enemies of aphids such as parasitic wasps. Wheat plants (Triticum aestivum) were genetically modified to produce and emit this pheromone. The genetic construct contained chemically synthesized gene sequences. Immature wheat embryos were transformed by microprojectile bombardment with the construct. Whole plants were regenerated and those that produced the pheromone were identified. Two different strains (“events”) of pheromone-producing GM wheat were selected for further investigation.

The researchers first grew the GM wheat plants in controlled greenhouse conditions. Aphids were fed on cut leaves of wheat and the pheromone was spread on the leaves. The aphids were “strongly repelled when exposed to volatiles collected from transformed plants grown in [laboratory] and field conditions.” In addition, parasitic wasps foraged more on aphids in these conditions.

When aphids were raised on the GM wheat plants for five generations in the lab, and then tested, one species of aphids hardly avoided feeding on leaves with pheromones, while another species was not at all repelled by them. This indicates habituation of the aphids to the pheromone over time.

Under field conditions, aphid populations in control plots (non-GM wheat plants) and GM plots were the same. Although the GM wheat plants produced the pheromone as they had in the lab, aphids were not repelled by them and there was no increase in aphids being parasitized by wasps.

These results highlight the often-found discrepancy between laboratory experimentation and the reality of field conditions, which are much more complex and unpredictable than those in the lab.

Bruce, T. J. A., G. I. Aradottir, L. E. Smart et al. (2015). “The First Crop Plant Genetically Engineered to Release an Insect Pheromone for Defence,” Scientific Reports vol. 5 no. 11183. Available online: doi:10.1038/srep11183.

Copyright 2015 The Nature Institute.

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