Due to a public referendum, commercial plantations of genetically modified (GM) crops are banned in Switzerland and this resulted in a bevy of research being conducted on the risks and benefits that GM foods provide.
Simon Zeller, the lead author on the study, says that one of the biggest problems associated with growing GM crops is that, if similar resistance genes are used in different crop species (known as “stacking”), pests could quickly acquire resistance to all of them. According to him, the mechanisms are similar to how bacteria develop multiple resistance in human medicine
“With the stacking of genes, you allow pathogens to acquire several resistances relatively quickly and each of these resistance genes is costly for the plant,” says Zeller. “It is possible that plants with several resistance genes show even higher resistance costs, which would lead to lower yields in years without pathogens.”
Therefore, Zeller and the other researchers planted two different lines of mildew-resistant genetically modified wheat together, apart and with a control (non-GM) wheat and monitored its resistance to mildew.
The researchers found that mildew resistance and yield increased with the concentration of GM wheat in the plots, especially in the plots containing a mixture of both GM plants (34.6 per cent less mildew infection compared to the control and a 6.5 per cent higher yield). According to Zeller, this could be because the resistant genes in both plants complemented each other and allowed for an increased resistance.
“The two plant lines hosted resistance genes against different locally occurring mildew strains,” he added. “This seemed to have limited the spread of these pathogens, which increased overall seed yield and we would also expect a pest population where no pathogen can dominate or acquire complete resistance.”
The researchers also noted that increasing the concentration of GM crops resulted in a low recorded Leaf Area Index and later flowering time, which may have been the biological cost caused by increased resistance. However, since mixing the two different lines resulted in a higher yield, the researchers hypothesize that increasing the amount of GM crops used could potentially further increase both resistance and yield.
“The logical next step would be to conduct similar experiments not only with mixtures and monocultures but also with plants with two or more stacked resistance genes,” said Zeller. “This would then allow testing our hypothesis that mixtures of single gene crops are indeed better than stacked crops.”