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Investigation of the establishment and persistence of GM potato volunteers and the potential consequences for current EU labelling thresholds for GM - CB0301

The objective of co-existence strategies for the cultivation of GM and non-GM crops is to facilitate public and farmer choice but to otherwise not prejudice GM or non-GM agriculture. To date, Defra has consulted on strategies for the coexistence of specific GM and non-GM crops grown on different farms. This current project is required to address an on-farm co-existence issue i.e. to inform Defra about the production of non-GM ware potato crops in fields where GM crops have been grown previously. In particular, Defra needs to know what research has been carried out on ware potato volunteer levels (and influencing factors) and whether further data are needed to inform future on-farm coexistence strategy.

The traceability and labelling regulations 1830/2003/EC require all marketed products containing an authorised GM presence to be labelled as GM. However an authorised presence of up to 0.9%GM is permitted in unlabelled marketed produce if this is adventitious or technically unavoidable. GM presence in otherwise non-GM crops is regarded as technically unavoidable if it results from a previous release of a GM crop where best practice to avoid volunteers has been followed.

No GM potatoes are grown commercially in England at present. However, there have been small-scale trials of GM potatoes for research purposes.

Defra is seeking information on the in-field persistence of potato volunteers with a view to determining whether and under what conditions the presence of GM volunteers in following non-GM potato crops could reach levels close to, or in excess of 0.9%.

Defra is interested in the emphasis that farmers place on controlling potato volunteers and to what extent control measures that are within the normal range of practices used, can minimise volunteer levels.


The project will comprise a desk study to determine to what extent the results of existing research on the incidence of potato volunteers can inform Defra about whether levels of GM potato volunteers are likely to be close to or above 0.9% in non-GM ware potato crops grown in successive rotations using the range of ‘normal’ agronomic practices.

The study will aim to explain how environmental, agronomic, varietal (including the significance of true seed) and commercial factors influence volunteer levels and persistence. It will detail the type and range of normal agronomic practices that are used to control potato volunteers. Consideration should be given to how these and other parameters (that affect volunteer numbers) may change over time and the relevance this has to the 0.9% threshold.

The study should highlight gaps in understanding and discuss whether these are significant in predicting whether the incidence of GM potato volunteers in successive non-GM potato crops is likely to be around or above 0.9%. Where appropriate, the study should make recommendations about what further information could be useful.

If the study shows that persistence close to, or above EU labelling thresholds is likely in non-GM ware potato crops grown in the following rotation, a proposal for further research should be drawn up. This would be to consider the agronomic options for controlling GM volunteers and any potential economic and environmental impacts associated with their adoption and to make recommendations regarding best practice to minimise the occurrence of GM potato volunteers in subsequent potato crops grown in the same field.
Time-Scale and Cost
From: 2008

To: 2009

Cost: £16,687
Contractor / Funded Organisations
Central Science Laboratory
Genetically modified food and crops              
GM Food              
GM Risk Assessment              
Fields of Study
Biotechnology and GMOs