Briefing: Summary of the risks of GM potatoes

Soil Association (UK) briefing on GM potatoes

Below is information on the risks of GM potatoes. This includes a summary from the report by the National Pollen Research Unit and other information on the risks of GM contamination of normal non-GM crops. Also evidence of
health problems.


- there would be no market for GM potatoes in the UK ·the major food retailers rejected GM potatoes in the US in 2002, including McDonalds, Burger King, McCain’s and Pringles. The British Retail Consortium has said UK supermarkets won’t be stocking GM potatoes.

- given that potatoes are a staple food, consumed fresh, and considered wholesome, there would be little or no desire to eat them ·any contamination would be much more serious as it would result in whole potatoes being GMOs, as opposed to some GM presence in a quantity of grain

- with potatoes, there is less direct risk of contamination of non-GM crops via cross-pollination than with GM grain and oilseed crops, as potatoes are tubers, not seeds

- however, there is still a risk of contamination from cross-pollination in later years via potato volunteers

- cross-pollination seems to be much greater when the GM and non-GM varieties are different and when the main pollinator is the pollen beetle, which travels far

- a study found the cross-pollination level was 31% at 1km from the GM crop

- blight resistant GM potato varieties pose much more of a risk of contamination as the flowering tops are less likely to be removed

- the NPRU has recommended a separation distance of 500m

- there are major health concerns, as two animal feeding trials, one funded by the UK Government, found GM potatoes cause lesions in the gut of animals

1. General

Potatoes are a staple food in the UK, and the fourth largest staple food in the world. Originally from South America, they have been grown in the UK for 300 years. Each person eats about 100kg per year, equivalent to 820 medium-sized potatoes. Potatoes are also used for industrial purposes, as a source of starch. The total area of potato production in the UK was 137,000t in 2005, of which 1,805t were organic (1.3% of the total area). Many varieties are grown in the UK.

2. Scientific evidence on the risks of contamination

The NPRU report on pollen dispersal reviewed the scientific literature on pollen transfer ("Pollen dispersal in the crops maize, oil seed rape, sugar beet and wheat", by Dr Treu and Prof. Emberlin, January 2000, commissioned by the Soil Association):

- the NPRU recommended a separation distance of 500m (in contrast with the proposal by Defra in August 2006 of no separation, their ‘co-existence’ paper)

- potatoes are an annual plant. The commercial crop is produced from ‘seed’ tubers, not true seeds. There are no sizeable seed producing areas in the UK.

- potatoes both self- and cross-pollinate. Cross-pollination rates are estimated to range from 0-20%

- cross-pollination is mainly by insects, mainly bumblebees - which tend to travel short distances, but can be by pollen beetles - which can fly far. The pollen beetle is “very common” in England

- ·potatoes pose a relatively low risk of cross-pollination because (i) potatoes are not grown from seeds but from tubers, which are clones of individuals of the desired variety, and (ii) the harvested crop is the tuber which is not affected by any cross-pollination

- however, potatoes produce volunteers, called ‘ground keepers’, and these pose a risk of GM contamination of non-GM crops in following years.

- importantly, the risk of cross-fertilisation is increased if (i) the GM and non-GM varieties are different but flower at the same time; (ii) if the varieties are blight resistant as the GM crop is more likely to be left flowering; or (iii) when the main pollinator is the pollen beetle, not bumblebees

- many varieties rarely produce berries as they are male sterile, but several modern varieties can produce very large numbers, each containing 400 seeds

- seed can survive seven years in southern England. When seeds grow, they mature into full potato plants, producing normal tubers, in the second year

- one study (Skogsmyr, 1994) found very high rates of cross-pollination between a GM variety (a version of Desiree) and a different non-GM variety (Stina), of 36% at 100m and 31% at 1km. This indicates that still considerable rates of cross-pollination would be occurring at greater distances. These high rates were attributed to the fact that higher levels of cross-pollination often occur between different varieties in outbreeding plants, and because the main pollinator in this case was probably the pollen beetle.

- two other studies found low levels of cross-pollination. It was assumed that this was partially because the main pollinator was bumblebees. In one study (McPartlan and Dale, 1994), the rates were 2% at 3m and 0.017% at 10m; the low rate was probably also because the GM and non-GM varieties were the same (Desiree). In the other (Tynan et al, 1990), the rate was 0.05% at 4.5m; a ‘wild type’ variety was used; the low rate of cross- pollination was probably also because the GM and non-GM varieties appeared to have a different flowering time.

- but these rates are probably considerable underestimates as these three studies were all only on a research plot scale, not using agricultural scale fields which would normally produce much higher rates of cross-pollination

- ‘relic’ potato plants from earlier crops can be found and persist on tips, waste grounds and fields

- potatoes are not interfertile with other crop or wild species

Defra has also considered the contamination risks from GM potato crops[1]:

- the main risk of GM potatoes is from cross-pollination of non-GM crops and GM volunteers appearing in later seasons: “the recipient plant will … produce GM hyrids, which means that GM volunteers may be created. It is
possible that over time there could be some limited GM transfer between farms via the development and persistence of GM volunteers.”

The NPRU says “the role of the pollen beetle in long distance distribution of potato pollen is in need of further research”. Further research into the significance of wind pollination in long range dispersal is also suggested.

3. Agricultural practices affecting the risk of GM contamination

- many different potato varieties are grown in the UK

- potatoes flower at similar times to the time when the tubers are being produced

- to prevent fungal ‘blight’ damage to the plant from affecting the growth of the potato tubers, farmers usually defoliate the plants, removing the flowering heads and green leaves (done with acids or, among organic farmers, mechanically or with flame-weeders). This is done at flowering or soon after. So, flowering is common, even if not present in most fields and generally only for short periods.

- after the defoliation, the crop is left for a few weeks to let the potato skins ‘set’

- however, the defoliation itself affects tuber growth, so farmers prefer to leave the green tops if they can. They are therefore more likely to leave the flowers if the varieties are blight resistant. This means that blight resistant GM varieties pose a higher risk of flowering presence, cross-pollinating and producing seed volunteers are usually controlled with herbicides but, according to Defra, “it is not possible to guarantee the complete elimination of volunteers”

- also, not every potato tuber will be removed from the ground

4. Organic potato production techniques

Organic farmers primarily control crop pests and disease with natural processes, including healthy soils, crop rotations and by encouraging natural predators. Blight in potatoes is one of the very few crop diseases where
such management techniques are not wholly effective, and instead late blight in organic farming is controlled by copper sprays. Copper is a naturally occurring element and many soils are deficient in it. The amounts used are
limited to 6kg/ha per year and it does not build up in the soil, due to the crop rotations. The copper is sprayed onto the plant’s leaves and does not end up in the potatoes, unlike the pesticides used in non-organic farming which
are found in a quarter of potatoes and may pose a risk to human health.

5. Development of GM potato varieties

The German chemicals group BASF has developed a blight resistant GM potato. It is currently trialling them in Germany, Netherlands and Sweden and has applied to Defra for approval to carry out two 1ha trials in the England in spring 2007 (one in Derbyshire and one in Cambridgeshire). After 3-4 years, they intend to seek permission to grow and sell the potatoes in Britain. The potatoes contain two genes from a wild Mexican potato.

According to BASF, the GM variety would reduce the number of fungicide sprays from about 15 per season to just a couple. These would be the first GM trials in the UK since the end of the farm-scale trails in 2003. BASF has also applied for EU approval for a potato that is rich in a type of starch used in the paper industry; it hopes for approval later this year.

GM potatoes are unnecessary and are unlikely to deliver significant environmental benefits. Only 1,300t of the 12,000t of pesticide used on potatoes in the UK are fungicides, so it seems that at most they could reduce
pesticide use by 10%.

Conventional breeding of existing varieties is making progress in developing blight resistant varieties. These are being developed and trialled for use in organic farming. Using old Hungarian varieties, Sarpo Mirea and Axona,
potato grower Dr David Shaw has developed blight resistant red varieties with a high dry content, suitable for chips and baking, and he is looking into a variety suitable for salads.

6.Commercial experience of GM potatoes

In the US, attempts at selling GM potatoes failed after being rejected by major food companies, including McDonald's, Burger King, McCain's and Pringles[2]. There are no GM potatoes sold in the US now. On the radio
programme, Farming Today, on 24 August 2005, Andrew Opie of the British Retail Consortium, representing supermarkets, said, “We won’t be stocking GM potatoes for the conceivable future ... The fact is people remain
suspicious of GM”.

7. Health problems with GM potatoes

There is a major concern that GM potatoes pose a risk to human health. There are many serious concerns about GMOs in general, most of which would apply to GM potatoes. However, there is a particular concern with GM
potatoes as for several years there has been evidence indicating that they could cause haemorrhages.

Feeding trials by two scientific teams found that GM potatoes cause lesions in the gut wall of rats and mice[3]. Both studies were published in scientific journals. One was a controlled UK Government funded study, peer reviewed
and published in the Lancet, the most respectable medical journal, in October 1999 (Ewen and Pusztai, 1999). The editor said the paper “deserved further scientific attention.”

The biotechnology industry reacted very aggressively and tried to mobilise the scientific community to undermine the credibility of the work. However, no further work has been undertaken since which could in any way suggest
that the finding was wrong. Moreover, the credibility of the findings is supported by the fact that similar effects have been found with GM tomatoes in two US feeding trials, which found that GM tomatoes cause lesions in the
gut wall of rats.[4]

GA, 24.8.2006, GM briefing 23

[1] “Consultation on proposals for managing the co-existence of GM, conventional and organic crops”, July 2006

[2] "GE crops - increasingly isolated awareness and rejection grow", Greenpeace International, briefing, March 2002

[3] Ewen and Pusztai, “Effects of diets containing genetically modified potatoes expressing Galanthus nivalis lectin on rat small intestine”, The Lancet, 354, 1353-1354, 1999; A. Pusztai, “Can science give us the tools for recognizing possible health risks of GM food?” Nutr. Health, 16, 73-84; Fares, N.H. and El-Sayed, A.K., “Fine structural changes in the ileum of mice fed on endotoxin-treated potatoes and transgenic potatoes.” Natural Toxins, 6, 219-233, 1998.

[4] Unpublished studies carried out for Calgene and at the request of the FDA respectively, in early 1990s, in reviewed “Food safety – contaminants and toxins”, CABI Publishing, 2003.