Journal of Economic Entomology (2016) 109, 307-319

Michael A. Caprio, Jeannette C. Martinez, Patrick A. Porter and Ed Bynum (2016)
The impact of inter-kernel movement in the evolution of resistance to dual-toxin Bt-corn varieties in Helicoverpa zea (Lepidoptera: Noctuidae)
Journal of Economic Entomology 109 (1), 307-319
Abstract: Seeds or kernels on hybrid plants are primarily F₂ tissue and will segregate for heterozygous alleles present in the parental F₁ hybrids. In the case of plants expressing Bt-toxins, the F₂ tissue in the kernels will express toxins as they would segregate in any F₂ tissue. In the case of plants expressing two unlinked toxins, the kernels on a Bt plant fertilized by another Bt plant would express anywhere from 0 to 2 toxins. Larvae of corn earworm [Helicoverpa zea (Boddie)] feed on a number of kernels during development and would therefore be exposed to local habitats (kernels) that varied in their toxin expression. Three models were developed for plants expressing two Bt-toxins, one where the traits are unlinked, a second where the traits were linked and a third model assuming that maternal traits were expressed in all kernels as well as paternally inherited traits. Results suggest that increasing larval movement rates off of expressing kernels tended to increase durability while increasing movement rates off of nonexpressing kernels always decreased durability. An ideal block refuge (no pollen flow between blocks and refuges) was more durable than a seed blend because the refuge expressed no toxins, while pollen contamination from plants expressing toxins in a seed blend reduced durability. A linked-trait model in an ideal refuge model predicted the longest durability. The results suggest that using a seed-blend strategy for a kernel feeding insect on a hybrid crop could dramatically reduce durability through the loss of refuge due to extensive cross-pollination.
(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): Michael A. Caprio

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.
	Helicoverpa zea	Maize/corn (Zea mays)
Bacillus thuringiensis genes in crops (entomopathogen)	Helicoverpa zea	Maize/corn (Zea mays)