Aug. 7, 2001 CLEMSON - Results of research, led by a Clemson University scientist, may lead to multi-millon dollar savings to the cotton industry and prolong the useful life of crops genetically modified to resist pests, the scientific team reported in the Aug. 3 issue of the journal Science.
Lead author Linda J. Gahan, an assistant professor of biological sciences at Clemson, and co-authors Fred Gould from North Carolina State University and David G. Heckel of the University of Melbourne, Australia, found an efficient method to track genetically the tobacco budworm's efforts to become resistant to biotechnological pest controls.
"We have identified a gene in the budworm which binds Bt-toxin produced in genetically modified plants like cotton," Gahan said. "If the gene is altered or defective in the insect, the insect will not bind the toxin and effectively becomes resistant to it. Knowing the gene involved in resistance allows us to develop a DNA test for monitoring resistance in field population of insects."
The tobacco budworm is a major pest of cotton and other field crops in the Americas. Over the years, it has developed resistance to chemical pesticides. The problem was solved through biotechnology when researchers added a gene to cotton from bacteria that naturally produces an insect toxin. The result was a genetically modified species, called Bt cotton, that resists the tobacco budworm and other insects.
Concerns took shape that the battle against the budworm was not a decisive victory. Under laboratory conditions, strains of tobacco budworms could be made Bt-resistant by feeding the insects a high-dose diet of the toxin. Federal regulators acted.
They required non-Bt cotton to be planted alongside of Bt cotton, diminishing the chances of budworms taking a Bt-rich diet in the fields. The question was how to monitor the situation, catching Bt resistance before it ended the usefulness of Bt cotton.
Developing an early-detection method had proved to be extremely difficult prior to Gahan's and her colleagues' breakthrough. Through DNA analysis, the researchers found that disruption of a gene could be linked to Bt-resistance.
"This is a first step to understanding the development of Bt-resistance by insect pests," Gahan said. "This discovery will open the door for other researchers and monitoring governmental agencies to assess resistance mechanisms and management strategies in insect pests. It will help us keep a handle on the development of insect resistance to Bt-genetically modified plants."
Gahan came to Clemson University in 1988 as an assistant professor/research associate in the biological sciences department. She and Heckel began mapping the Heliothis virescens (tobacco budworm) genome in 1991. Heckel left in 1999 to become a senior lecturer in the genetics department at the University of Melbourne. Prior to leaving Clemson, he received funding from the National Science Foundation to find the Bt-resistant gene in the tobacco budworm, resulting in the research conducted by Gahan, Heckel and Gould over the past two years.
Gahan earned a bachelor's degree in chemistry at Bucknell University in 1964 and a Ph.D. in biochemistry at the University of Illinois in 1968.
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