Trials of Genetically Modified Aphid-Resistant Wheat Fail

Despite promising results in the laboratory, trials of a genetically modified strain of wheat designed to be resistant to aphids have ended in disappointment. Aphids can cause widespread destruction of a crop as they feed on sap, while some species also inject a toxin that causes the plant’s leaves to wither giving the aphid a safe place to lay their eggs.

The wheat in question had been modified to release a warning pheromone that would ward off aphids while also attracting the aphid’s natural enemies such as parasitic wasps. This in turn would reduce the amount of insecticides needed to be sprayed by farmers. Parasitic wasps lay eggs inside the aphid eventually killing it, and when aphids are faced with such wasps they will release a chemical alarm warning other aphids away. This alarm however, attracts more wasps causing a cycle of aphid elimination.

Based on this natural cycle, researchers designed a new gene based on one in peppermint that would release such a chemical warning and designed it to work in wheat. In the laboratory the wheat successfully released the warning pheromone, repelling three kinds of aphids while also attracting parasitic wasps. In pursuant field trials, scientists planted 16, six meter-square plots with the GM wheat, but the team reported in Scientific Reports that there was no statistical difference in aphid number between the GM plots and non-GM plots.

Scientists believe that because the plants continuously released the warning pheromone instead of in short bursts as an aphid would when attacked, it became a case of ‘the plant that cried wolf’, making the insects ignore the signal after a period of time. The team is considering further work to create a wheat plant that released a burst of pheromone only when eaten by an aphid, but such field trials will be years in the future.