Author:Heidi Ledford
Researchers at National Autonomous University of Mexico and the University of Arizona in the U.S. have modified Bt toxins to make it more difficult for insects to develop resistance. Their work has been published in the journal Science. More work will need to be done to see whether plants can be genetically engineered to produce the modified form of toxin, according to the article. Bruce Tabashnik, an entomologist at the University of Arizona and a member of the research team, says it is "almost inevitable" that insects will develop resistance to the Bt toxin. So far, the article says resistance has only been documented in the field for two insects: diamondback moths (Plutella xylostella ) and cabbage loopers (Trichoplusia ni), both of which produce larvae that feed on vegetable crops. The resistant insects have only been found in fields and greenhouses where Bt is sprayed as an environmentally-friendly pesticide, not in fields planted with Bt-producing genetically modified (GM) crops. The article says that biotechnology companies are pursuing several options to prevent Bt resistance from developing among insect populations. These include selling GM crops that contain two different Bt toxins which bind to separate receptors found in insect guts. Researchers are also developing plants that produce an entirely different toxin, normally made by bacteria that live in nematode worm guts. William Moar, an entomologist at Auburn University in U.S., comments that the modified Bt toxin could make a useful addition to this "arsenal."
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