Organic Farming And Transgene Pollution From Genetically Modified Crops

David Heaf

In May 1999 the John Innes Centre published a lengthy discussion paper with 107 references titled Organic Farming and Gene Transfer from Genetically Modified Crops by Catherine L. Moyes and Philip J. Dale. The paper was the result of a mainly bibliographic research project funded by the Ministry of Agriculture, Fisheries and Food.1 This article is a critical commentary on that paper.

The paper takes as its point of departure the regulations that were applied at that time by the United Kingdom Register of Organic Food Standards (UKROFS), but as it came out before the new European regulation on Genetically Modified Organisms (GMOs) in organic agriculture published in August 19992 it is already a little out of date. Nevertheless, Moyes and Dale’s conclusions are not at odds with the new regulation.

The authors begin by identifying the possible routes of crop contamination. This is summarised by their Figure 1 which is reproduced here:

heaf2.gif (4893 bytes)

The diagram omits seed distribution by animals and the theoretically possible routes of transgene flow involving both naked and organism-integrated DNA via animal feeds, manure, soil and alimentary tract microflora, although these are acknowledged in the body of the text of the paper. More research would be needed to establish how significant these routes are in practice.

The paper lists the extensive research already carried out on separation distances versus seed purity for 14 crops or crop classes and acknowledges that low levels of pollen dispersal can be detected at kilometre distances. However, pollen deposited at such distances is not necessarily viable. Even so, where no actual genetic pollution has occurred, i.e. insertion of transgenes into the genome of a crop at risk, there remains a concern about contamination by genetically modified (GM) pollen or seeds physically present in the organic crop. Like genetic pollution, such contamination would also show up on the gene tests. This means that where Moyes and Dale write in paragraph 4.4 "plants...grown for vegetative parts e.g. root crops and leaf vegetables...will not be affected by contamination from pollen", they are wrong.

Where crops are perennial and home-saved seed is propagated over several years, small contaminations could be cumulative. Unfortunately, very few studies have considered gene flow from crops over many seasons. Furthermore, contamination by GM seed is potentially worse than by pollen if the GM seed then goes on to produce volunteer plants. This is because the separation distance from the GM variety falls to zero.

Genetic engineering is still in its infancy and, as the paper points out, in the fullness of time GM crops may be produced with modified pollen characteristics or breeding systems such that gene flow is lessened. This brings to mind the so called terminator technology whereby seeds saved from the first sowing and harvest are sterile because they contain transgene complexes which are toxic to the developing embryo.

Moyes and Dale show that seed dormancy up to 5 years can present a problem for following crops. The draft revision to the UKROFS Standards for Organic Food Production and Soil Association’s draft Genetic Engineering Standards Guidance Notes (August 1999) both provide for prohibiting organic production on land that has been planted with GM crops in the previous 5 years. Whether the 5 year period adequately accommodates the theoretical route of contamination from naked DNA in the soil or from transgenes, e.g. antibiotic resistance genes, which have established themselves in the soil microflora, is unknown.

The most fundamental position in the organic sector is that the very presence of a transgene, rather than the effect it has, is of concern. Moyes and Dale acknowledge the existence of this position. They write that ‘the chance that a crop may be contaminated above an acceptable level can never be entirely excluded’ and ‘if no level of contamination is acceptable then this cannot be guaranteed.’ (Para. 6.1) For the organic sector, the bottom line in the whole discussion paper reads: ‘It is important to define acceptable levels because complete isolation cannot be guaranteed.’ (Para. 6.3) But to their credit, the authors admit that the organic sector ‘may require higher standards in order to provide the consumer with an acceptable level of GM-free food.’ (Para. 8.4) Even so, as the whole point of the paper is that transgenes cannot be completely contained the authors seem to be calling upon the organic sector to define an acceptable level of contamination. The new European organic regulation2 would appear to be preparing the ground for just this. The relevant paragraph in this regulation states:

‘The following may be adopted in accordance with the procedure laid down in Article 14: [...] implementation measures according to scientific evidence or technical progress to apply the prohibition on the use of GMOs and GMO derivatives with regard, in particular, to a de minimis threshold for unavoidable contamination which shall not be exceeded.’

If the organic sector including Demeter/BDAA does not want to be steered down the road to de minimis thresholds for GM contamination then it will need to develop robust arguments for its position that GM-free means zero transgenes. This is because a consequence of this position is that it will make it extremely difficult to conventional farmers who wish to grow GM crops to do so. Achieving such a consequence is an expressed aim of the Soil Association.3

If plans for de minimis thresholds become more concrete the question will be asked as to what levels of contamination are acceptable to the organic sector. Paradoxically, certain elements of the GM seed industry want very low limits to be set. The thinking here is that the lower the level, the sooner the whole organic sector will become contaminated thus bringing closer the day when a distinction between GM and non-GM need no longer be made.

Based on the years of experience in the seed industry regarding separation distance versus seed purity the Supply Chain Initiative on Modified Agricultural Crops (SCIMAC), a voluntary body of the seed industry set up to police the large scale trial and commercial planting of GM crops, has established separation distances for planting GM crops near non-GM crops.4 For the GM crops currently close to commercialisation, these are summarised in the following table:

Crop type

Certified seed crops (same species)

Registered organic crops (same species)

Non-GM crops (same species)

Oilseed rape




Sugar beet




Fodder beet




Forage maize



200m sweetcorn

50m forage maize

If the UK organic sector continues to hold to the position that GM-free means ‘zero contamination’ then in the light of the Moyes and Dale paper these separation distances will be totally inadequate. At the instigation of UKROFS and the Ministry of Agriculture, Fisheries and Food in September 1999 the organic sector and SCIMAC were brought to the discussion table. It was an acrimonious meeting in parts and whilst the fundamental positions of both sides remain unchanged it is difficult to see how organic and biotechnological agriculture can coexist in the future.


1. This paper is downloadable from the John Innes Centre’s gmIssues web site at and can be ordered from the authors at John Innes Centre, Colney Lane, Norwich, NR4 7UH

2. COUNCIL REGULATION (EC) No 1804/1999 of 19 July 1999 supplementing Regulation (EEC) No 2092/91 on organic production of agricultural products and indications referring thereto on agricultural products and foodstuffs to include livestock production. Published in the Official Journal of the European Community on 24th August 1999 (L 222 1-28, URL:, follow link "1").

3. Patrick Holden, personal communication, 14 May 1999.

4. Code of practice on the introduction of genetically modified crops (May 1999), Guidelines for growing newly developed herbicide tolerant crops (no publication date) and The genetically modified crop management guide (Summer 1999) are all available from SCIMAC, Woolpack Chambers, Market Street, Ely, Cambs CB7 4ND.

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