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Submitted to: Southwestern Entomologist
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 7/23/2010 Publication Date: 9/29/2010 Citation: Fabrick, J.A. 2010. Insights into the genetics and molecular mechanisms of pink bollworm resistance to cry toxins. Southwestern Entomologist.35:431-435. Interpretive Summary: Bacillus thuringiensis (Bt) toxins are expressed in transgenic Bt crops to control key insect pests. The pink bollworm is an insect pest of cotton and is currently the target of an area-wide eradication program with the purpose to eliminate pink bollworm from cotton-producing areas of the U.S. and adjacent areas of northern Mexico. Transgenic Bt cotton is a key component of the program. Insecticide resistance to Bt is the genetically based decrease in susceptibility of an insect population caused by previous exposure to Bt. Evolution of resistance to Bt cotton by pink bollworm could jeopardize the eradication program and diminish success of long-term control. Continuous monitoring for resistance in pink bollworm indicates that pink bollworm resistance in the U.S. remains rare. However, recent discovery of field-evolved resistance to Bt cotton in India emphasizes the need for diligent resistance monitoring and stewardship of the Bt transgenic technology. A lab-selected strain of pink bollworm is highly resistant to a Bt toxin produced in Bt cotton and differs from previously characterized resistant pink bollworm strains. Technical Abstract: Transgenic crops producing Bacillus thuringiensis (Bt) Berliner (Bacillales: Bacillaceae) toxins target key insect pests in cotton and corn cropping systems. The pink bollworm, Pectinophora gossypiella (Saunders) (Lepidoptera: Gelechiidae), is currently the target of an area-wide eradication program with the purpose to eliminate pink bollworm from cotton-producing areas of the U.S. and adjacent areas of northern Mexico. Transgenic Bt cotton is a key component of the program. Evolution of resistance to Bt cotton could jeopardize the eradication program and diminish success of long-term control of PBW populations. Molecular monitoring for known resistance alleles and bioassays indicate that pink bollworm resistance to Bt cotton in U.S. remains rare. However, recent discovery of field-evolved resistance to Bt cotton in India emphasizes the need for diligent resistance monitoring and stewardship of the Bt transgenic technology. Resistance to Cry1Ac in lab-selected strains of pink bollworm may involve at least two different resistance mechanisms, based on characterization of cadherin-based resistant strains and a newly selected Bt4R strain. In all previous resistant strains of pink bollworm, resistance involved mutations in a cadherin gene encoding for a functional Cry1Ac toxin receptor. Selection of the Bt4R strain using Bt cotton bolls and Cry1Ac in diet revealed a novel mechanism of resistance that differs from previously described cadherin mutations. |
