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article imageGM crop fails to kill caterpillars

By Tim Sandle     Sep 26, 2013 in Environment
Whether GM crops are right or wrong for the environment, they are supposed to pest resistant. In one case, however, African caterpillars have proved to be remarkably resistant.
Bt maize has been planted in various parts of the African continent. As well as boasting improved yields, the crop is supposed to be resistant to most types of pests. One type of ‘pest’, the moth Busseola fusca, has developed a defense mechanism against the genetically enhanced toxin contained within the maize.
Genetically engineered maize is created by introducing a gene into the plant genome that expresses a toxic protein from a bacterium. With the case of Bt maize this is the bacterium Bacillus thuringiensis (Bt). The intention is that the leaves and stems of Bt maize produce a toxin which destroys the gut of any moth larvae eating the plant. The maize was first planted in South Africa during the 1990s.
Specifically, when an insect eats the Bt-containing plant, the protein is activated in the gut of the insect, which is alkaline (human guts are acidic), and in the alkaline environment the protein partially unfolds and is cut by other proteins, forming a toxin that paralyzes the insect's digestive system and forms holes in the gut wall. The insect stops eating within a few hours and eventually starves to death
The toxin has not proved effective and not only have Busseola fusca caterpillars resisted the toxin, they have grown and spread in number. The caterpillar is sometimes called the ‘Maize Stalk Borer’. It is unlikely, however, that the resistance will cause a re-think when it comes to GM crops, most likely a new type of crop will be developed designed to act against the moth.
Researchers have written about the moth and its resistance in the journal PLoS ONE. The paper is titled “Dominant Inheritance of Field-Evolved Resistance to Bt Corn in Busseola fusca.”
More about Gmo, Genetically modified, Crops, Maize, Caterpillars
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