Monsanto Co. scientists have developed a technique to improvethe expression of insecticides in plants.

Previous insertions of Bacillus thuringiensis (Bt) insect toxingenes into cotton, tobacco and tomatoes resulted in plants thatproduced the toxin, but not at high enough levels to make theplants resistant to insects.

Now, according to a report in the latest Proceedings of theNational Academy of Sciences, researchers have modified Bttoxin genes to improve toxin production 10- to 100-fold intomatoes and tobacco. Monsanto spokesman Gary Barton saidthese levels are close to what are needed to render plantsresistant to lepidopteran insects such as moths.

The scientists modified Bt genes in a way that improved theplant's ability to translate Bt toxin RNA into protein.

Last summer Monsanto conducted seven field tests of cottoncontaining similarly designed Bt genes, said Barton. Only 4percent of these plants were attacked by boll worms and budworms, compared with 31 percent of untreated plants.Monsanto predicts that such insect-resistant plants couldreduce insecticide usage by 40 percent.

Jerry Caulder, president of Mycogen Corp., said that theseresults are extremely important to companies that aregenetically engineering insect-resistant plants.

Mycogen sprays Bt toxins onto plant leaves, enabling thecompany to protect any plant against insects that aresusceptible to the toxins, said Caulder. He said Monsanto's andMycogen's approaches were complementary. The companiesare working together to develop nematode roundworm-resistant plants.

-- Carol Talkington Verser, Ph.D. Special to BioWorld

(c) 1997 American Health Consultants. All rights reserved.