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article imageSweet potatoes are naturally 'genetically modified'

By Tim Sandle     Apr 23, 2015 in Food
Scientists have serendipitously established that sweet potatoes naturally contain genes from a bacterium. Due to the presence of “foreign” DNA, a research report calls sweet potatoes the “natural GM food.”
The phrase "natural GM" is designed by the research group behind the discovery to be headline grabbing. Nonetheless, the discovery is of interest. Scientists unexpectedly found foreign DNA sequences of a bacterium called Agrobacterium while searching the genome (the entire DNA code) of sweet potato. This exercise was being undertaken in order to assess the types of viruses that can infect the sweet potato and ruin crops. The presence of the bacterial DNA is the result of a type of horizontal gene transfer. This where there is an exchange of genes occurs between different species.
This process is the basis of current GMO (genetically modified organism) technology, whereby variants to existing crops are created in order to be more robust or to produce a better yield. Genetically modified foods are foods produced from organisms that have had specific changes introduced into their DNA using the methods of genetic engineering.
The sweet potato (Ipomoea batatas) is a large, starchy, sweet-tasting, tuberous roots are a root vegetable. Raw sweet potatoes are rich in complex carbohydrates, dietary fiber and beta-carotene.
To check whether the presence of the bacterial genetic information was an aberration or something common, the researchers examined some 291 tested sweet potato cultivars. The presence of the same bacterial DNA was found in all samples. This finding infers that this association had been going back hundreds of years and that farming practices had inadvertently selected potatoes with the bacterial DNA because this produced a better crop.
Further analysis showed that Agrobacterium is specialized to transfer a part of its own DNA, the so-called T-DNA, to plants. This discovery demonstrates that genetic modification also happens in nature.
The research is important because the sweet potato is a globally important food crop. It may be possible to use the existing mechanisms to further enhance the way that sweet potatoes resist diseases.
The study is a collaboration between UGent and the International Potato Institute (CIP). The findings have been published in the journal Proceedings of the National Academy of Sciences, in a research paper titled “The genome of cultivated sweet potato contains AgrobacteriumT-DNAs with expressed genes: An example of a naturally transgenic food crop.”
More about sweet potatoes, Genetics, Genetically modified food, Genetically modified organisms
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