Crops Potatoes

Over the last few years, potatoes have been losing importance as a food crop. The crop's prospects in the starch and chemical industry, however, have been growing for quite some time. For starch potatoes, taste isn't what's important. Instead, emphasis is placed on the quality and composition of the starch. An optimised starch potato could be making its way to fields in Europe soon. This new potato cultivar is genetically modified.

Only one in four potatoes grown in Europe actually gets eaten by people. Almost half end up being fed to livestock. The remaing one quarter are used as raw material in the production of alcohol and starch.

Coming to a farm near you: GM potatoes with modified starch composition could soon be grown in Europe. Discontinued: GM potatoes resistant to the potato beetle (Photo: larva) have disappeared from the North American market. Goals for the future: GM potatoes resistant to late blight are now being tested in the field. (Photo: magnification of the fungus)

Potatoes are becoming more and more important as renewable raw materials for the starch industry. The starch produced in potatoes, however, isn't in an ideal form. It's composed of a mixture of two different kinds of starch: amylose and amylopectin. These two kinds of starch have very different properties. Amylopectin, making up 80 percent of the starch content in potatoes, consists of large, highly-branched molecules. Amylopectin makes starch water soluble and gives it its characteristic stickiness. It is very useful in the food, paper, and chemical industries as paste, glue or as a lubricant. Amylose is made up of long, chain-like molecules and is used predominantly in the production of films and foils. Both of these kinds of starch are useful for human nutrition. But for the processing industry, a mixture of different starches is a problem. Industry must separate the two kinds of starch using expensive processes that take a toll on the environment. This is why plant breeders are working hard to develop potatoes that produce only one type of starch. Right now, emphasis has been placed upon developing potatoes containing only amylopectin, due to its diverse applications. Classical breeding methods have not yet been able to provide an amylose-free potato that has acceptable yield and resistance to pests and diseases. Genetic engineering (Antisense-Strategy), on the other hand, offers a targeted approach to supressing the production of amylose.

Genetically modified amylopectin potatoes have been tested in field trials for several years. In the meantime, applications have been presented to European regulatory authorities for approving the cultivation of these potatoes as a renewable raw material for starch production. Because the post-processing residues would be fed to livestock, a request for the approval of the potatoes as feed has also been submitted. Starch-modified GM potatoes could be growing in European fields soon.

Resistance to pests and diseases

Attempts to confer pest and disease resistance to potatoes using genetic engineering haven't been quite as successful.

• Several GM potato cultivars with improved resistance to viruses and to the potato beetle have been approved in the US and in Canada. In 1999, they were planted on approximately 25,000 hectares. Since then, cultivation of GM potatoes has ceased. The GM potatoes did not prevail, because they were not delivering any economic advantages, and some larger US companies refused to take the GM potatoes for further processing.

• Right now, work is being done on potatoes with genetic engineering to confer resistance to Phytophthora infestans, also known as late blight of potato. Some consider this to be the most dangerous plant disease of all because it can spread extremely rapidly when conditions are warm and moist, leading to devastating losses. The disease is best known for causing the Irish Potato Famine of 1846-1850. Today, the disease is still a major problem. Owing to its flexibility, the disease has been able to survive every management strategy used thus far and has responded with new, adapted forms. Today, the disease is combatted using fungicides and heavy metal treatments. In the meantime, genetic engineers have come up with a promising new strategy. The first field trials with fungus resistant GM potatoes are already underway. The next few years will show if this new concept is effective.

See also on GMO-Compass:

• GMO Database: Starch modified potato
• GMO Food Database: Potato