Less than almost zero safety testing

January 2015

CC photo by International Maize and
Wheat Improvement Center on Flickr
In recent years, more than a quarter of the GM crops in commercial production were 'stacked' with more than one artificial gene construct (or 'event'). Such plants have been produced by breeding single-construct varieties together until all the desired GM traits were together in a single crop.

Despite the recognition that crossing two GMOs will produce an entirely novel GMO, stacked plants are being approved on the unjustifiable basis that all their parent GMOs have been approved.

Even in Europe, which has arguably the most stringent GM regulations in the world, and requires a full risk-assessment, stacked GMOs have been approved without investigation of the final product.

At the end of 2014, the first study was published which looked at the metabolic consequences of breeding plants with two artificial gene constructs from single-event parent GMOs.

The Brazilian-Norwegian team of scientists compared a double 'Bt' insecticidal GM maize and a herbicide-tolerant GM maize with progeny containing both sets of genes. It also compared all three with a non-GM equivalent control, and with a non-GM traditional maize 'normal' background comparator.

Their results indicate that the regulators' lax attitude to the safety of stacked GM crops could be putting consumers and farmers' livelihoods at risk.

Protein profiling revealed significant differences between the proteins in stacked GM maize, single-event lines and their conventional counterpart. Some of these differences fell outside the range of natural variability represented by the traditional maize comparator.

The proteins altered mainly involved energy production (suggesting the GM plants' physiology was stressed) and detoxification (suggesting a response to a harmful presence). Proteins involved at fundamental levels of genetic information processing and cellular processes were also affected (suggesting a widespread disruption to normal functioning). Unpredictable harmful materials could be part-and-parcel of any of these physiological perturbations.

Of concern to farmers was the finding that the expressed levels of the Bt insecticides and of the protein intended to neutralise a herbicide were reduced by about one-third in the stacked variety. Besides inadequate pest-control, insufficient levels of insecticide are known to promote pest-resistance [1]. Inadequate ability to deal with herbicide applications will damage the crop as much as the weeds.

A disturbing possibility put forward by the authors is that the depression of gene expression in the stacked GM crop might arise from the transgenes silencing each other due to the presence of similar ('homologous') DNA sequences. The expression of both the Bt and the herbicide-tolerance genes in the GM plants studied are driven by a Cauliflower Mosaic Virus (CaMV) promoter.

The authors confirmed what had previously been found, that protein profiles vary much more due to the plants' genetic background, crop management and environmental factors such as season and geography, than due to the presence of the artificial genes. This reinforces the point that safety testing of GM food can only be done using GM and non-GM isogenic plants grown side-by-side, and that the crude measurements of total protein and protein breakdown products used for nutritional evaluation are totally worthless for safety studies.


It seems we have a situation of almost-zero valid safety testing of GM in general , and less-than-almost zero safety testing of stacked GM products. 

As predicted, as soon as scientists apply more sophisticated tests, GM safety is called into question.

Demand a halt to GM food until the science used in risk-assessment has caught up with the wild technological advances.


[1] THE BT PEST REFUGE THAT ISN'T - December 2014

  • Sarh Zanon Agapito-Tenfen, et al., 2014, Effect of stacking insecticidal cry and herbicide tolerance epsps transgenes on trangenic maize proteome, BioMed Central Plant Biology 14, 10.12.14
  • Stacking traits in a GMO is found to cause unexpected synergistic effects, GM Watch 2014,

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