ngin - Norfolk Genetic Information Network
29 December 2002

GM crops are breeding with plants in the wild
By GEOFFREY LEAN, Environment Editor
Independent on Sunday, 29 December 2002

Alarming new results from official British trials of GM crops are severely jeopardising plans for growing them commercially.

The findings - in a new government report - show, for the first time in Britain, that genes from GM crops are interbreeding on a large scale with conventional ones, and with weeds.

The study is so devastating to the Government's case for GM crops that ministers sought to bury it by publishing the first information on it on the Department of the Environment, Food and Rural Affairs website on Christmas Eve. That is the one day in the year when no newspapers are being prepared. Even then it only produced a heavily edited summary of the main report. Unusually the full report, which will contain much more devastating detail, was withheld from publication on the website.

The department said that it was available on request, but when The Independent on Sunday tried to ask for it last week, the department said that no one was available to provide it.

The report, the result of six years of monitoring of GM crops in Britain, is politically explosive and gives the first results from the official farm-scale trials. The Government has repeatedly said the results would settle the question on whether GM crops endangered the environment. But it has been playing down their significance in recent weeks.

The trials, set up in the face of public hostility to the crops, were not designed to look at the possibility of genes from GM crops contaminating nearby plants, but at the effects of different uses of pesticides on GM and non-GM plants. But, following criticism, studies of this "gene flow" were added later.

The studies, carried out between 1994 and 2000 by the National Institute of Agricultural Botany and the Laboratory of the Government Chemist, shows that genes from GM oil seed rape, engineered to be resistant to herbicides, contaminated conventional crops. And GM oil seed rape that had escaped from a crop harvested in 1996, persisted for at least four years. The report also shows that the GM crop interbred with a weed, wild turnip, giving it resistance to herbicides and thus raising the prospect of the development of super weeds.

Pete Riley of Friends of the Earth said the results showed that if GM crops became widespread, almost all similar crops would become contaminated, threatening organic agriculture.

"It is not surprising the Government has tried to cover this up. It shows we need to know a great deal more about these issues before we contemplate growing GM crops commercially."


Genetically Modified Organisms Research


The report represents the combined final reports of two separate Defra monitoring contracts run between 1994-1997 and 1997-2000. A summary of the final report is available below. Copies of the full report are available on request from See also ACRE's Advice on this publication.



In 1994 the National Institute of Agricultural Botany (NIAB) and the Laboratory of the Government Chemist (LGC) were commissioned by the Department of the Environment, Transport and the Regions (DETR) to monitor the first agricultural releases of genetically modified (GM) oilseed rape (OSR) for a three year period. Subsequently NIAB received a second contract in 1997 to continue monitoring releases of GM OSR including all the previously studied sites and any new sites over 1ha. The contracts also required NIAB to conduct studies of monitoring methods and of the flow of transgenes to crops and wild relatives. The monitoring terminated at the end of 2000.

The first crops monitored were seed production crops sown in spring 1995 and 1996. Two 5ha areas of GM winter OSR sown in the autumns of 1995 and 1996, were also monitored. The seed production crops monitored were for the production of the Plant Genetics System (PGS) GM hybrid oilseed rape and consisted of a GM male-sterile female parent line, interplanted with a pollinator containing a male fertility restorer gene, and both lines containing the Bar marker transgene conferring tolerance to the herbicide glufosinate-ammonium. The winter rape areas were PGS trials containing a mixture of GM and non-GM parent lines and hybrids. The transformations were similar to those in the spring rape.

>From 1997 several new sites containing trials or crops of glufosinate (Bar and Pat genes) and glyphosate tolerant transgenic varieties were monitored. In 1998, several sites growing a high laurate transgenic spring OSR variety were included in the monitoring study. In 1999 the monitoring included the two first Farm Scale Evaluation (FSE) trials of GM OSR and provided an opportunity to study gene flow between two large adjacent blocks of spring OSR at these sites. By the year 2000, a total of 11 sites that had grown GM OSR were being monitored. All sites continued to be monitored in the years following the GM OSR crop or trial until the end of 2000.

The monitoring programme studied the characteristics of herbicide-tolerant transgenic rape which were most likely to effect the crop, the cultivated and the non-cultivated environment. These characteristics were assumed to be the same as those of non-transgenic rape, namely dispersal into and colonisation of these environments and gene flow into other crops, feral populations and wild crucifers. The following factors were studied and comparisons made between the behaviour of transgenic OSR and conventional OSR where possible.  Intra-specific gene flow Gene flow was monitored from GM OSR crops to adjacent crops, OSR volunteers and feral rape populations.

No intra-specific gene flow was detected at any of the sites monitored between 1994 and 1997. During this time none of the GM release sites were near to other synchronously flowering oilseed rape crops. No gene flow was detected to OSR volunteers and feral OSR growing near the GM releases monitored at any of the sites during this period.

In the period 1998 to 2000 gene flow was detected from GM trials into adjacent OSR crops. At one of the FSE sites gene flow decreased rapidly with distance from the pollen source. However at both FSE sites, levels of herbicide-tolerance in excess of 0.5% were found in some samples taken at 100m from the source while at one FSE site levels of herbicide-tolerance in excess of 0.5% were found in some samples taken at 200m, though the overall trend was for gene flow to decrease with distance. These could have resulted from several factors including, adventitious GM material in the original seed batch of Hyola 401, the possible presence of male-sterile individuals, weather conditions or a combination of these and other unknown factors.

Gene flow was also measured from 2 GM trials into adjacent fields of OSR in 2000. Gene flow levels were found to be substantially higher into a varietal association than a conventional variety, due to the male sterile component of these systems. Levels up to 3.2% herbicide tolerance were found at the edge of one field of the varietal association Gemini, at 105m distance from a small block of transgenic herbicide tolerant OSR. By contrast when a transgenic herbicide tolerant trial pollinated a neighbouring conventional crop of the variety Apex, at a different site, maximum levels of outcrossing at 100m were 0.2%. However at most sampling points less than 0.1% herbicide tolerance was found 70m from the pollen source.

Inter-specific gene flow

Gene flow was monitored between GM OSR and related cruciferous species. In the first three years of the contract (1994 to 1997) a wider range of crucifers was monitored including Capsella bursa-pastoris (shepherd's purse) and Sisymbrium officinale (hedge mustard). When the contract was renewed in 1997 it was considered that resources should be concentrated on species considered to be important candidates for hybridisation with OSR. The species that continued to be monitored were Brassica rapa (wild turnip), Raphanus raphanistrum (wild radish), Sinapis arvensis (charlock) and Sinapis alba (white mustard).

No gene flow was detected from OSR into the related species examined in this study during the period 1994 to 1997. Between 1997 and 2000 hybridisation was detected with B.rapa. One site was examined where weedy B.rapa occurred in an agricultural field. Hybridisation frequencies varied between plants and were between 0.0% and 48.5%. When seeds were germinated from hybrid mother plants, some evidence of backcrossing in the direction of both parents (B.napus and B.rapa) was also found. Backcrossing to B.napus plants was identified by their ploidy level, however back-crossing to B.rapa plants could not always be determined by their ploidy level as in many cases this was the same as or very similar to the ploidy level of B.rapa. The co-existence of the B rapa populations with B napus crops and the numbers of hybrids found, suggested that gene flow has been occurring for some time between these populations.
Seed dispersal

Seed dispersal was usually associated with spillage and distribution by agricultural machinery, particularly combine harvesters. In the contract from 1994 to 1997, it was found that some combine harvesters were not cleaned after the harvesting of the GM crop, and the crop harvested subsequently flushed out the GM rape seed onto the ground causing contamination of this field .

GM OSR volunteers found in fields were generally controlled in the same way as conventional volunteers. Outside the cultivated area establishment and survival of seedlings was very poor, and few feral transgenic OSR plants survived to maturity

Persistence of transgenic OSR volunteers

The persistence of transgenic OSR volunteers was compared to existing data and observations of non-transgenic volunteers. The numbers of GM OSR winter and spring volunteers were generally low in subsequent crops. The presence of a herbicide-tolerance transgene or high laurate transgene did not appear to increase the weediness or persistence of volunteer OSR in this study.

Feral Oilseed Rape

Only one feral OSR population was found to persist for more than one year at any of the sites being monitored. The herbicide-tolerance Bar gene was not detected in any of the feral OSR plants so that effects on weediness and persistence of these populations could not be assessed.

Development of optimal methodology for monitoring

A practical, effective and economical combination of monitoring methodology was developed to cover all the above aspects of monitoring. This included familiarity with the species and sites involved, combined with phenotypic and genotypic testing for the presence of the transgene. The combination of methods used ensured that any major impacts of the GM plants on the agricultural and local environment occurring at each site were likely to be observed.


The high levels of isolation from other OSR crops flowering synchronously, and the relatively small GM pollen sources and low levels of cruciferous weeds present at the sites, limited potential gene flow at the sites  monitored in the first 3-year contract (1994 to 1997). Larger trials or crops released during the second 3-year contract (1998 to 2000) and the closer proximity of pollen receptive crops and related wild species allowed greater opportunities for gene flow to be studied. The results from these larger trials and crops indicate that commercial scale releases of GM OSR in the future could pollinate other crops and B.rapa, the levels of cross pollination depending on the environmental, varietal and agronomic factors prevailing at the time. There may be a need to review isolation requirements in keeping with current legislation on contamination thresholds in crops, in light of this research.

Page published 24 December 2002; last modified 24 December, 2002

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