Journal of Economic Entomology (2008) 101, 1406-1414

Carlos A. Blanco, O.P. Perera, Fred Gould, Douglas V. Sumerford, Gerardo Hernández, Craig A. Abel and David A. Andow (2008)
An empirical test of the F₂ screen for detection of Bacillus thuringiensis-resistance alleles in tobacco budworm (Lepidoptera: Noctuidae)
Journal of Economic Entomology 101 (4), 1406-1414
Abstract: Insects exposed to genetically modified crops expressing Bacillus thuringiensis (Bt) toxins are under intense selection pressure that could result on widespread Bt resistance. Screening for early indications of Bt resistance developing in targeted Lepidoptera is conducted in many of the regions where genetically modified cotton and corn have been commercialized. Heliothis virescens (F.) (Lepidoptera: Noctuidae) has been selected in the laboratory to have a gene for resistance to Cry1Ac. We used this laboratory line to test the assumptions and theoretical predictions related to detection of recessive Bt-resistant alleles in field populations based on a second generation (F₂) screen. By creating single-pair families from mating a heterozygous Cry1Ac-resistant moth with a Cry1Ac-susceptible moth, we simulated the most common genotype when Bt-resistance alleles are at low frequency in the field. The second generation (F₂) neonates of single-pair families were screened daily with diagnostic concentration bioassays. Cry1Ac-resistant homozygous larvae were detected, but the proportion of resistant larvae was generally below the theoretical expectation of 6.25% and was influenced by the moth F₁ sib-mating density and by the day of oviposition of F₂ eggs. Logistical considerations such as F₁ sib-mating density and F₂ neonate screening are important for the successful implementation of a reliable method.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Link to article at publishers website
Database assignments for author(s): Carlos A. Blanco, Omaththage P. Perera, Craig A. Abel

Research topic(s) for pests/diseases/weeds:
biocontrol - natural enemies
Research topic(s) for beneficials or antagonists:
resistance/tolerance/defence of host

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Heliothis virescens	Maize/corn (Zea mays)
Bacillus thuringiensis genes in crops (entomopathogen)	Heliothis virescens	Maize/corn (Zea mays)
Bacillus thuringiensis Cry1A-toxin (entomopathogen)	Heliothis virescens	Maize/corn (Zea mays)