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18.12.2017 |

Cases of Pest Resistance to Bt Crops Increased Five-fold From 2005-2016

Transgenic or genetically modified Bt (Bacillus thuringiensis) crops (mainly corn, cotton and soybean) cover more than 830 million hectares worldwide. In addition to the crystalline (Cry) proteins from Bt produced by transgenic crops for the past two decades, some recently introduced types of Bt corn and cotton produce a vegetative insecticidal protein (Vip) from Bt.

The efficacy of Bt crops has been threatened by the evolu­tion of pest resistance. A recent study analyzes relevant literature on this topic from the past two dec­ades to elucidate the current status of pest resistance to transgenic crops. Compared with previous reviews on this topic, the field-moni­toring data analyzed in this study represent a more diverse set of Bt toxins (one Vip and nine Cry toxins), crops (corn, cotton, and soy), pests (15 species from two insect orders), and countries (ten countries on six continents).

The study found that the number of cases of pest resistance to Cry proteins produced by transgenic crops increased from 3 in 2005 to 16 in 2016. For the 16 cases of practical resistance, the average time for evolution of resistance was only 5.2 years. In four situ­ations, practical resistance has reduced the number of Bt toxins that are available in commercialized transgenic crops and are still effective against some pest populations to two, one, or none.

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