Baseline Susceptibility to Cry1Ac Insecticidal Protein in Heliothis virescens (Lepidoptera: Noctuidae) Populations in Brazil

The tobacco budworm, Heliothis virescens (F.), is one of the target pests of genetically modified cotton expressing Cry1Ac insecticidal protein (Bt cotton) derived from Bacillus thuringiensis Berliner. This study was conducted to evaluate the susceptibility of field-collected populations of H. vires...

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Bibliographic Details
Published in:Journal of economic entomology 2013-08, Vol.106 (4), p.1819-1824
Main Authors: Albernaz, K. C, Merlin, B. L, Martinelli, S, Head, G. P, Omoto, C
Format: Article
Language:English
Subjects:
Animals
Bacillus thuringiensis - genetics
Bacterial Proteins - pharmacology
Brazil
Bt cotton
Dose-Response Relationship, Drug
Endotoxins - pharmacology
Gossypium - genetics
Hemolysin Proteins - pharmacology
insect resistance management
Insecticide Resistance - drug effects
INSECTICIDE RESISTANCE AND RESISTANCE MANAGEMENT
Insecticides - pharmacology
Larva - drug effects
Larva - growth & development
Lethal Dose 50
Moths - drug effects
Moths - growth & development
Pest Control, Biological
Plants, Genetically Modified - genetics
tobacco budworm
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Summary:The tobacco budworm, Heliothis virescens (F.), is one of the target pests of genetically modified cotton expressing Cry1Ac insecticidal protein (Bt cotton) derived from Bacillus thuringiensis Berliner. This study was conducted to evaluate the susceptibility of field-collected populations of H. virescens to Cry1Ac to establish a baseline for use in an insect resistance management program for Bt cotton in Brazil. Insects were sampled from the main Brazilian cotton-growing regions (Bahia, Mato Grosso, Mato Grosso do Sul, and Goiás) during the cropping seasons of 2007/08 and 2008/09. Cry1Ac susceptibility was estimated by using diet incorporation bioassays. H. virescens was highly susceptible to Cry1Ac protein. The estimated LC50 values varied from 0.18 to 0.66 µg of Cry1Ac/ml of diet among the 2007–2008 populations (≈3.7-fold variation). Similarly, the EC50 values based on growth inhibition ranged from 0.0053 to 0.0161 µg of Cry1Ac/ml of diet for the 2007–2008 populations («3.0-fold variation ). A joint analysis of the mortality data across all tested populations was used to develop and validate the diagnostic concentrations of 3.1 and 5.6 µg of Cry1Ac/ml of diet, the upper bound of the confidence interval and twice the LC99 were selected, for resistance monitoring programs of H. virescens to Cry1Ac protein in Brazil.
ISSN:0022-0493
1938-291X
0022-0493
DOI:10.1603/EC12222