An analysis of genetically modified (GM) maize has found differences between a herbicide-tolerant GM maize variety and its genetically similar non-GM counterpart.

The report, published on Monday in the journal Scientific Reports, is the first to raise questions about ‘substantial equivalence’ which is used by regulators in risk assessing GM crops. It was authored by a group of scientists including Dr Michael Antoniou, a geneticist from King’s College London and Gilles-Eric Serallini, the author of a hugely controversial study from 2012 which found health effects from feeding GM maize to rats.

The team looked at NK603 maize, sold as Round-up Ready 2. The EU Commission re-approved NK603 for sale in the EU in 2015, after the EU’s legislative bodies failed to reach an agreement on the maize in either standing or appeals committees in 2014.

According to Dr Antoniou and colleagues, previous studies that have compared GM and non-GM crops have reported differences, but these haven’t been strong enough be deemed “biologically significant,” as they can fit into the range of comparisons that could be drawn between two conventionally bred crops, or could be put down to the environment or different growing conditions.
The researchers used a different analysis tool from industry and regulators, which they said is more in-depth and allowed them to examine the types of proteins and other smaller molecules (metabolites) present in the GM maize and its non-GM counterpart. The researchers’ main finding was that the two varieties “are not substantially equivalent”; they also identified higher numbers of polyamines (compounds that perform essential functions in living cells) in the GM maize, but they are uncertain whether this would have a harmful or helpful effect on animals consuming the grains.

They are confident that the differences observed can be put down to the genetic modification process, but said that further growing tests under different environmental conditions would be needed to establish a full range of differences between a GM variety and a non-GM isogenic comparison crop.

Commenting on the findings, Dr Dan MacLean from The Sainsbury Laboratory, said the compounds (metabolome and proteome) highlighted by the researchers as being different in the two maize types are very variable even “Under tight laboratory conditions”, which could explain the results.

Discussing their own work and previous studies, the researchers said in their paper “Neither genetic differences nor environmental variations alone can account for the production of a particular phenotypic variation.”

Also commenting on Monday, Johnjoe McFadden, Professor of Molecular Genetics at the University of Surrey, said, “The science is good as far as it goes. But the analysis only emphasises the inadequacy of the ‘substantial equivalence principle’. How equivalent does it need to be? If you perform this detailed level of analysis on any perturbation of any organism you will detect this level of change – organisms are extraordinary sensitive and, for example, similar changes are produced when treated with e.g. pesticide or herbicides1 or when attacked by pests2.

“I would expect that practically any perturbation to an organism will generate a response that can be detected by these powerful techniques – that is after all what life does. So all it shows is that GM, like pesticides, herbicides, drought, predation or even growing in a different field will produce a response by the organism.”