Genetic modification to fight potato late blight

(Photo: Agricultural Research Service, United States Department of Agriculture, public domain)

Potato late blight causes huge losses for potato farmers, and leads to excessive use of fungicides. Genetically modified potato may help solve the problem, but Norwegian law requires an assessment of whether this potato contributes to sustainability. How do we assess that?

Potatoes come in many varieties and dishes that are familiar and dear to most of us. But, did you know that potatoes, like us humans, are plagued by viruses, bacteria and fungi?

Potato late blight is considered to be the most devastating potato disease worldwide. It is caused by a fungus that spreads easily from plant to plant by fungal spores carried by wind and rain. Infected tubers become brown, unattractive and unsuitable for sale. Today farmers fight the disease with excessive use of chemical fungicides. More than half of the fungicides used in Norwegian agriculture is used to control late blight.

Researchers have for decades worked to develop potato varieties that are resistant to late blight. They do this by crossing commercial potato varieties with wild – inedible – potatoes from South America that are naturally resistant to the disease. It has however proven to be difficult to develop potato varieties with durable resistance, as late blight has an incredible ability to overcome the potato plant’s defense mechanisms. 

When scientists genetically modify potatoes to resist diseases, they must first identify the genes that make wild growing potato varieties resistant. These genes are called resistance genes. The scientists then exploit the natural ability of a soil bacterium (Agrobacterium) to transfer the resistance genes into the genome of commercial potato plants.

Many argue that GM is the best approach to make potatoes with more durable resistance, as it makes it easier to introduce several resistant genes into the same potato variety. The Norwegian Gene Technology Act demands that a GMO must benefit society, contribute to sustainable development and be ethically acceptable in order to be approved for cultivation or commercialization. But, how can the authorities evaluate whether this type of GM potato satisfies these criteria?  That is what we have tried to find out in a research project.

Several European research teams are currently developing late blight resistant GM potato, and different GM potato varieties are tested in field trials throughout Europe. These field trials have shown that GM potato can reduce the use of fungicide to control late blight with up to 80% in Europe. The American company J.R. Simplot has also developed late blight resistant GM potato varieties and approval for cultivation in the US is expected early in 2017. GM potatoes that only harbor resistance genes from naturally crossable relatives are called cisgenic. This is in contrast to transgenic plants in which the genes are derived from completely different species, such as bacteria.

People have different opinions about what the meaning of sustainability, social utility and ethics is. We wanted to find out what potato farmers and other stakeholders think is essential to include in an assessment of these criteria, and organized three seminars during 2014 and 2015 to do so. Both farmers and professionals from the potato industry attended the seminars, in addition to researchers on potato and plant diseases, potato breeders, agricultural advisors and representatives of environmental and consumer organizations.

During the seminars we wanted to identify questions that are important to assess in order to evaluate whether late blight resistant GM potato satisfies the requirements in the Gene Technology Act. Key questions suggested by the participants were:

  • Does cultivation of GM potatoes reduce use of fungicides?
  • Is the late blight resistance of the GM potato plants durable?
  • Are GM potatoes safe for human health and the environment in the long term?
  • Does cultivation of GM potatoes increase the profitability for potato producers over time?
  • Will consumers eat GM potatoes?
  • Does cultivation of GM potatoes affect consumers' perception of Norwegian food as clean and safe?
  • Will the cultivation of GM potatoes affect the diversity of commercial potato varieties and farmers opportunity to grow conventional and organic potatoes?
  • Does the developers of GM potatoes facilitate transparency and good communication with the public and authorities?
  • Are GM potatoes available for further breeding or research by other scientist?

Several other questions were brought up for discussion. For instance; Will patented GM potatoes restrict farmers' ability to use potatoes from their own crop as seed potatoes? Is there reason to assume that cisgenic GM potatoes, which only have received genes from other potatoes plants, are safer than transgenic potatoes? Do Norwegian consumers want to eat GM potato? Many perceive Norwegian food as clean, safe and of good quality, while they are more skeptical to GM food. Agriculture is dependent on trust. Can cultivation of GM potato challenge this trust relationship?  Or will a GM potato that is less exposed to fungicides and only harbors genes derived from other potato species, make people less skeptical to GM food?

Finally, the genetic diversity of the Nordic late blight population is particularly high and this strengthens the adaptive potential of the pathogen. Is there therefore a reason to assume that the GM potato plant’s resistance will be broken faster in Norway than elsewhere in Europe?

Some participants were convinced that this type of GM potato would benefit farmers and contribute to more sustainable agriculture as they expected that farmers would spray less with chemical fungicides. They also emphasized that there is little risk that GM potato will spread to the surroundings. Potato tubers do not spread as easily as seeds, and there are no wild relatives for GM potato to cross with in Norway.

This type of GM potato is the first example in a GM plant that can contribute to solve a serious problem for Norwegian and European agriculture, and it opens for an interesting discussion about sustainability, ethics and social benefit. It also raises broader questions, such as; What is the future of Norwegian agriculture and how may GM crops affect the perception of Norwegian food? These are questions that we all ought to consider.

Written by: Frøydis Gillund, Researcher GenØk – Centre for Biosafety

Reference:

Gillund, F., Myhr, A.I., Utskarpen, A., & Hilbeck, A. (2016). Stakeholder views on issues to consider when assessing the sustainability of genetically modified potato, International Journal of Agricultural Sustainability. DOI: 10.1080/14735903.2016.1140013

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