Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

First Documented Case of Pest Resistance to Biotech Cotton

08.02.2008
A pest insect known as bollworm is the first to evolve resistance in the field to plants modified to produce an insecticide called Bt, according to a new research report.

Bt-resistant populations of bollworm, Helicoverpa zea, were found in more than a dozen crop fields in Mississippi and Arkansas between 2003 and 2006.

"What we're seeing is evolution in action," said lead researcher Bruce Tabashnik. "This is the first documented case of field-evolved resistance to a Bt crop.”

Bt crops are so named because they have been genetically altered to produce Bt toxins, which kill some insects. The toxins are produced in nature by the widespread bacterium Bacillus thuringiensis, hence the abbreviation Bt.

The bollworm resistance to Bt cotton was discovered when a team of University of Arizona entomologists analyzed published data from monitoring studies of six major caterpillar pests of Bt crops in Australia, China, Spain and the U.S. The data documenting bollworm resistance were first collected seven years after Bt cotton was introduced in 1996.

"Resistance is a decrease in pest susceptibility that can be measured over human experience," said Tabashnik, professor and head of UA's entomology department and an expert in insect resistance to insecticides. "When you use an insecticide to control a pest, some populations eventually evolve resistance."

The researchers write in their report that Bt cotton and Bt corn have been grown on more than 162 million hectares (400 million acres) worldwide since 1996, “generating one of the largest selections for insect resistance ever known."

Even so, the researchers found that most caterpillar pests of cotton and corn remained susceptible to Bt crops.

"The resistance occurred in one particular pest in one part of the U.S.,"
Tabashnik said. "The other major pests attacking Bt crops have not evolved resistance. And even most bollworm populations have not evolved resistance."

The field outcomes refute some experts' worst-case scenarios that predicted pests would become resistant to Bt crops in as few as three years, he said.

“The only other case of field-evolved resistance to Bt toxins involves resistance to Bt sprays," Tabashnik said. He added that such sprays have been used for decades, but now represent a small proportion of the Bt used against crop pests.

The bollworm is a major cotton pest in the southeastern U.S. and Texas, but not in Arizona. The major caterpillar pest of cotton in Arizona is a different species known as pink bollworm, Pectinophora gossypiella, which has remained susceptible to the Bt toxin in biotech cotton.

Tabashnik and his colleagues' article, "Insect resistance to Bt crops:
evidence versus theory," will be published in the February issue of Nature Biotechnology. His co-authors are Aaron J. Gassmann, a former UA postdoctoral fellow now an assistant professor at Iowa State University; David W. Crowder, a UA doctoral student; and Yves Carrière, a UA professor of entomology. Tabashnik and Carrière are members of UA's BIO5 Institute.

The U.S. Department of Agriculture funded the research.

"Our research shows that in Arizona, Bt cotton reduces use of broad-spectrum insecticides and increases yield," said Carrière. Such insecticides kill both pest insects and beneficial insects.

To delay resistance, non-Bt crops are planted near Bt crops to provide "refuges" for susceptible pests. Because resistant insects are rare, the only mates they are likely to encounter would be susceptible insects from the refuges. The hybrid offspring of such a mating generally would be susceptible to the toxin. In most pests, offspring are resistant to Bt toxins only if both parents are resistant.

In bollworm, however, hybrid offspring produced by matings between susceptible and resistant moths are resistant. Such a dominant inheritance of resistance was predicted to make resistance evolve faster.

The UA researchers found that bollworm resistance evolved fastest in the states with the lowest abundance of refuges.

The field outcomes documented by the global monitoring data fit the predictions of the theory underlying the refuge strategy, Tabashnik said.

Although first-generation biotech cotton contained only one Bt toxin called Cry1Ac, a new variety contains both Cry1Ac and a second Bt toxin, Cry2Ab.

The combination overcomes pests that are resistant to just one toxin.

The next steps, Tabashnik said, include conducting research to understand inheritance of resistance to Cry2Ab and developing designer toxins to kill pests resistant to Cry1Ac.

Researchers' disclosure of competing financial interests:
Although preparation of this article was not supported by organizations that may gain or lose financially through its publication, the authors have received support for other research from Monsanto Company and Cotton, Inc.
One of the authors (B. T.) is a co-author of a patent application filed with the World Intellectual Property Organization on engineering modified Bt toxins to counter pest resistance, which is related to research published in

2007 (Science 318: 1640-1642. 2007).

Researcher contact information:
Bruce Tabashnik, 520-621-1141
brucet@ag.arizona.edu
language: English

Yves Carrière, 520-626-8329
ycarrier@ag.arizona.edu
languages: English and French
Related Web sites:
Bruce Tabashnik
http://ag.arizona.edu/ento/faculty/tabashnik.htm
Yves Carriere
http://ag.arizona.edu/ento/faculty/carriere.htm
UA Department of Entomology
http://ag.arizona.edu/ento/
UA College of Agriculture and Life Sciences http://ag.arizona.edu/
UA's BIO5 Institute
www.bio5.org

Mari N. Jensen | University of Arizona
Further information:
http://www.arizona.edu

More articles from Agricultural and Forestry Science:

nachricht Researchers discover natural product that could lead to new class of commercial herbicide
16.07.2018 | UCLA Samueli School of Engineering

nachricht Advance warning system via cell phone app: Avoiding extreme weather damage in agriculture
12.07.2018 | Leibniz-Zentrum für Agrarlandschaftsforschung (ZALF) e.V.

All articles from Agricultural and Forestry Science >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: First evidence on the source of extragalactic particles

For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.

To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...

Im Focus: Magnetic vortices: Two independent magnetic skyrmion phases discovered in a single material

For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.

Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...

Im Focus: Breaking the bond: To take part or not?

Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.

A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...

Im Focus: New 2D Spectroscopy Methods

Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.

"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....

Im Focus: Chemical reactions in the light of ultrashort X-ray pulses from free-electron lasers

Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.

Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Leading experts in Diabetes, Metabolism and Biomedical Engineering discuss Precision Medicine

13.07.2018 | Event News

Conference on Laser Polishing – LaP: Fine Tuning for Surfaces

12.07.2018 | Event News

11th European Wood-based Panel Symposium 2018: Meeting point for the wood-based materials industry

03.07.2018 | Event News

 
Latest News

Microscopic trampoline may help create networks of quantum computers

17.07.2018 | Information Technology

In borophene, boundaries are no barrier

17.07.2018 | Materials Sciences

The role of Sodium for the Enhancement of Solar Cells

17.07.2018 | Power and Electrical Engineering

VideoLinks
Science & Research
Overview of more VideoLinks >>>