Potatoes.
Over the last 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 composition and quality of starch. An optimised, genetically modified starch potato could be making its way to fields in Europe soon. Only one in four potatoes grown in Europe actually gets eaten by people. Almost half end up being fed to livestock. The remaining one quarter are used as raw material in the production of alcohol and starch. 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-branced 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 only produce 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 suppressing 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 authorization as feed has also been submitted. Starch-modified GM potatoes could be growing in European fields soon.

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. Farmers did not consider them to be an economic advantage, and a few major potato processors in the US chose to keep their products free of GM potatoes. Right now, genetic engineering work is being done on potatoes to confer resistance to Phytophthora infestans, also known as late blight of potato. Late blight is the disease responsible for Irish Potato Famine of 1846-1850. Many consider it to be the most dangerous plant disease in the world because of how rapidly it can spread when conditions are warm and moist, causing devastating losses. Owing to its flexibility, it has been able to survive every management strategy used thus far and has responded with new, adapted forms. The disease is now being managed with 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 truly effective.

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