lunes, septiembre 26, 2005

Bt cotton failure

Scientists Confirm Failures of Bt-Crops

Ineffective against insect pests, harmful to health and biodiversity, yield drag, pest resistance. Dr. Mae-Wan Ho

Scientific studies from many countries have now backed up what farmers have known for years, that Bt crops – genetically engineered with Bt toxin proteins from the soil bacterium Bacillus thuringiensis targeted at insect pests - often failed to protect against pest attacks, and have other problems as well.

Scientists in India, China and the United States found that the levels of Bt toxin produced by Bt crops vary substantially in different parts of the plant and in the course of the growing season, and are often insufficient to kill the targeted pests. This could lead to greater use of pesticides, and accelerate the evolution of pest resistance to the Bt toxin. Pest resistance to a Bt toxin has indeed arisen in the field in Australia.

The Bt toxins are a family of similar Cry proteins identified by numbers and letters. Each Cry protein differs somewhat in amino acid sequence and targets specific pests.

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