Vip3A resistance alleles exist at high levels in Australian targets before release of cotton expressing this toxin

Crops engineered to produce insecticidal crystal (Cry) proteins from the soil bacterium Bacillus thuringiensis (Bt) have revolutionised pest control in agriculture. However field-level resistance to Bt has developed in some targets. Utilising novel vegetative insecticidal proteins (Vips), also deriv...

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Bibliographic Details
Published in:PloS one 2012-06, Vol.7 (6), p.e39192
Main Authors: Mahon, Rod J, Downes, Sharon J, James, Bill
Format: Article
Language:English
Subjects:
Agricultural management
Agriculture
Alleles
Animals
Australia
Bacillus thuringiensis
Bacillus thuringiensis - physiology
Bacterial Proteins - genetics
Bacterial Proteins - metabolism
Bacterial Toxins - pharmacology
Binding sites
Biology
Colonies & territories
Corn
Cotton
Crops
Cry1Ac toxin
Ecosystems
Endotoxins - genetics
Endotoxins - metabolism
Genetically modified crops
Gossypium - metabolism
Helicoverpa armigera
Helicoverpa punctigera
Helicoverpa zea
Hemolysin Proteins - genetics
Hemolysin Proteins - metabolism
Host-Pathogen Interactions
Insecticide resistance
Insecticide Resistance - genetics
Insects
Laboratories
Lepidoptera
Lepidoptera - drug effects
Lepidoptera - genetics
Lepidoptera - microbiology
Mutation
Mutation rates
Neonates
Noctuidae
Pest control
Pest Control, Biological
Plants (botany)
Protein expression
Proteins
Seasonal variations
Seasons
Soil microorganisms
Spodoptera frugiperda
Toxins
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Summary:Crops engineered to produce insecticidal crystal (Cry) proteins from the soil bacterium Bacillus thuringiensis (Bt) have revolutionised pest control in agriculture. However field-level resistance to Bt has developed in some targets. Utilising novel vegetative insecticidal proteins (Vips), also derived from Bt but genetically distinct from Cry toxins, is a possible solution that biotechnical companies intend to employ. Using data collected over two seasons we determined that, before deployment of Vip-expressing plants in Australia, resistance alleles exist in key targets as polymorphisms at frequencies of 0.027 (n = 273 lines, 95% CI = 0.019-0.038) in H. armigera and 0.008 (n = 248 lines, 0.004-0.015) in H. punctigera. These frequencies are above mutation rates normally encountered. Homozygous resistant neonates survived doses of Vip3A higher than those estimated in field-grown plants. Fortunately the resistance is largely, if not completely, recessive and does not confer resistance to the Bt toxins Cry1Ac or Cry2Ab already deployed in cotton crops. These later characteristics are favourable for resistance management; however the robustness of Vip3A inclusive varieties will depend on resistance frequencies to the Cry toxins when it is released (anticipated 2016) and the efficacy of Vip3A throughout the season. It is appropriate to pre-emptively screen key targets of Bt crops elsewhere, especially those such as H. zea in the USA, which is not only closely related to H. armigera but also will be exposed to Vip in several varieties of cotton and corn.
ISSN:1932-6203
1932-6203
DOI:10.1371/journal.pone.0039192