Zeaxanthin potatoes

New potatoes – a remedy for blindness in old age?

Genetically modified potatoes that accumulate the carotenoid zeaxanthin in their tubers are expected to protect against age-related blindness. The zeaxanthin potato is not likely to be released onto the market in the immediate future, but researchers are investigating possible effects of these potatoes on the quality of agricultural soils as part of biosafety research.

Tubers of the zeaxanthin potato (left) have a darker, deeper yellow colour than the parent variety Baltica (right)

The zeaxanthin potato is a potato with a modified carotenoid composition. Carotenoids are ‘plant secondary metabolites’ that occur in many species of vegetable. They are reputed to have a protective effect against degenerative diseases.

The zeaxanthin carotenoid is an essential component of the yellow spot (macula) on the retina. The macula is responsible for central vision and allows us to see clearly and appreciate fine details. Evidence suggests that an increased intake of zeaxanthin can prevent age-related macular degeneration, one of the most common causes of blindness in Germany and other industrialised countries.

Only a few vegetables, including orange peppers and green cabbage, contain appreciable amounts of zeaxanthin. Potatoes do produce zeaxanthin in their tubers, but it is converted by an enzyme. The genetic modification blocks this enzyme, enabling the accumulation of up to 130 times the normal concentration of zeaxanthin in the tuber.

Uphill battle: Deliberate release trials regularly destroyed

The zeaxanthin potato was developed by a group project funded by the Federal Ministry of Education and Research (BMBF) on “Improving the health quality of food by increasing and modifying the carotenoid content “. Many public research establishments and private companies were involved in the project. The aim was to increase the carotenoid content in various plant species using genetic engineering and other modern plant-breeding methods. The zeaxanthin potato was viewed as a so-called ‘functional food’, i.e. the researchers wanted to accumulate health-promoting substances in a staple food.

At the end of April 2003 these potatoes were planted for the first time for research purposes, following prior authorisation by the Robert Koch Institute, on the Roggenstein trial estate by the Chair of Plant Cultivation and Breeding (Technische Universität München). The aim was to produce a sufficient number of genetically modified potatoes in the field to be able in the first instance to carry out a thorough nutritional physiology study of the harvested tubers. According to the release application, in the following years the researchers intended to conduct research into e.g. outcrossing of the transgenic traits to potato varieties planted in parallel.

However, two months later, the trial field was destroyed by unknown perpetrators. As a result, the studies could no longer continue as planned. There had been vehement protests against the release even during the authorisation procedure. The municipality of Olching, environmental associations and the Munich Environmental Institute (Umweltinstitut München) had submitted numerous objections. They focused on questions of environmental safety and in particular on an antibiotic-resistance gene used as a marker in the transgenic potatoes. The municipality of Olching eventually brought legal action against the authorisation decision, which led to more stringent safety requirements for the release experiment.

Model biosafety research plant

Since 2005 research into the biological safety of the zeaxanthin potato has been conducted in Roggenstein (2005 and 2007) and at another site in Oberviehausen (2006 and 2007). The zeaxanthin potato is being used here as a test organism for crops with modified substances. Within the safety research into transgenic plants funded by the BMBF there are two projects investigating the impacts of these potatoes on soil microflora, bacteria and fungi in the root zone.

In 2006 trials at the Technical University of Munich were initially suspended due to an administrative error by the Federal Office of Consumer Protection. In April 2006 a deliberate release trial was once again destroyed, when unknown perpetrators poured oil onto the fields. The soil contaminated during the oil attack had to be removed to a depth of thirty centimetres, and the trial could no longer be evaluated.

Both three-year projects investigating the effect of the zeaxanthin potato on microbial soil flora will come to an end in 2008.