Huge groups of consumers have shown resistance to the use of genetic modification in food production. Can genetically modified or manipulated components end up in mushrooms via the soya used in supplements? PPO investigated.

European consumers in particular demonstrate an enormous aversion to GM (Genetically Modified) food, which has lead to European legislation stating that all products containing more than 0.9 % ingredients originating from GM products must be labelled. This measure grants consumers a measure of choice. A zero limit was not chosen as growing and using GM crops is already so widespread that it's very difficult to obtain completely GM-free products. GM-soya in particular is very widely grown, and huge numbers of food products contain soya.

The supplements used in mushroom growing nearly all list soya among their ingredients. Many buyers of fresh and processed mushrooms want guarantees that mushrooms are free of any genetically modified material. Foreign buyers importing Dutch mushrooms mainly demand this. The question is: Can GM components end up in mushrooms via supplements?

RoundupReady soya

Via genetic modification GM-soya was made resistant to the crop protection agent Roundup. This means soya growers can easily keep their fields weed-free. The active substance in Roundup is glyphosate. GM-soya was made resistant to this substance by introducing a piece of DNA (gene) into the soya plant that produces a protein allowing the plant to break down the glyphosate ‘Sandwiched’ around this gene are other genetic components, which enhance the effect of the added gene. Highly sensitive, advanced techniques exist that can identify the presence of DNA in many products. However, the sequence of the building blocks of the DNA to be identified must be known beforehand. This sequence is known for all genetic components used in GM-soya. PPO applied this existing knowledge to test if it is possible for GM components in supplements to end up in mushrooms. The Product Board Horticulture funded this research.

The test

To test the method we used certified material already available on the market: un-modified soya (SB0) and samples in which 0.5% (SB0.1) or 5% (SB5) of the beans were genetically modified (mixed batches). As a control a test was used to detect the gene for a natural soya component (soya lectine). In all the tests, the SB0 samples were negative and the SB0.1 and SB5 samples positive. The test for the soya-lectine gene was always positive.

This control demonstrates that we isolated intact DNA from the soya. Dilution series showed that the test for the GM-component is so sensitive that even one GM-soya bean in five thousand non GM-soya beans can be identified.

This test was then applied to two supplements. The test could identify both the lectine of soya and the GM-component. The test also works on supplements.

The test was run on mushrooms cultivated on supplemented compost. Both washed and unwashed mushrooms were used, as in principle it could be possible for mushrooms to be contaminated by raw materials which would then show GM components on the exterior of the mushroom, while the mushroom has not actually absorbed any of them. GM components from supplements did not show in either of the mushroom samples tested.

We then tried some harder tactics by growing mushroom mycelium on a medium with as its sole nutrient GM soya beans (0.2% of the medium contained soya beans prepared from SB5, the remainder of the medium was water and agar). No GM-components were found in this mycelium. As this medium was sterilised before use we first tested if sterilisation had any influence on the identification of GM components in the soya. The test could detect the GM components in sterilised and in un-sterilised soya.

GM-free

The conclusion we can draw is that it is out of the question for GM components from supplements to be in or on mushrooms. This result is not entirely unexpected. Moulds produce all types of protein that first partially decompose the nutrients surrounding mycelium. Only then can the mycelium start to absorb the small particles. It is therefore highly improbable, if not impossible, that intact DNA coding for the GM part of the process could arrive at any stage in the mushroom.

Similar research has also been recently carried out on pigs. Here too, no GM-components were found in the pork after the animals had been fed varying amounts of GM-soya meal. Trade and consumers alike can rest assured. Mushrooms are GM-free, even if GM products are used in the raw production materials.  Plus, there are no GM-mushroom varieties on the market.