TY - JOUR
T1 - Effects of seasonal changes in cotton plants on the evolution of resistance to pyramided cotton producing the Bt toxins Cry1Ac and Cry1F in Helicoverpa zea
AU - Carrière, Yves
AU - Degain, Ben A.
AU - Unnithan, Gopalan C.
AU - Harpold, Virginia S.
AU - Heuberger, Shannon
AU - Li, Xianchun
AU - Tabashnik, Bruce E.
N1 - Funding Information:
We thank Peter Ellsworth for help with obtaining cotton cultivars used in this study. This study was supported by US Department of Agriculture (USDA) Biotechnology Risk Assessment Grant Awards 2011-33522-30729 and 2014-33522-22214 and by funding from Cotton Inc.
Publisher Copyright:
© 2017 Society of Chemical Industry
PY - 2018/3
Y1 - 2018/3
N2 - BACKGROUND: In pests with inherently low susceptibility to Bacillus thuringiensis (Bt) toxins, seasonal declines in the concentration of Bt toxins in transgenic crops could accelerate evolution of resistance by increasing the dominance of resistance. Here, we evaluated Helicoverpa zea survival on young and old cotton plants that produced the Bt toxins Cry1Ac and Cry1F or did not produce Bt toxins. RESULTS: Using a strain selected for resistance to Cry1Ac in the laboratory, its parent strain that was not selected in the laboratory, and their F1 progeny, we showed that resistance to Cry1Ac + Cry1F cotton was partially dominant on young and old plants. On Cry1Ac + Cry1F cotton, redundant killing was incomplete on young plants but nearly complete on old plants. No significant fitness costs on non-Bt cotton occurred on young plants, but large recessive costs affected survival on old plants. Simulation models incorporating the empirical data showed that the seasonal changes in fitness could delay resistance to Cry1Ac + Cry1F cotton by inducing low equilibrium frequencies of resistance alleles when refuges are sufficiently large. CONCLUSION: Our results suggest that including effects of seasonal changes in fitness of pests on Bt crops and refuge plants can enhance resistance risk assessment and resistance management.
AB - BACKGROUND: In pests with inherently low susceptibility to Bacillus thuringiensis (Bt) toxins, seasonal declines in the concentration of Bt toxins in transgenic crops could accelerate evolution of resistance by increasing the dominance of resistance. Here, we evaluated Helicoverpa zea survival on young and old cotton plants that produced the Bt toxins Cry1Ac and Cry1F or did not produce Bt toxins. RESULTS: Using a strain selected for resistance to Cry1Ac in the laboratory, its parent strain that was not selected in the laboratory, and their F1 progeny, we showed that resistance to Cry1Ac + Cry1F cotton was partially dominant on young and old plants. On Cry1Ac + Cry1F cotton, redundant killing was incomplete on young plants but nearly complete on old plants. No significant fitness costs on non-Bt cotton occurred on young plants, but large recessive costs affected survival on old plants. Simulation models incorporating the empirical data showed that the seasonal changes in fitness could delay resistance to Cry1Ac + Cry1F cotton by inducing low equilibrium frequencies of resistance alleles when refuges are sufficiently large. CONCLUSION: Our results suggest that including effects of seasonal changes in fitness of pests on Bt crops and refuge plants can enhance resistance risk assessment and resistance management.
KW - balanced polymorphism
KW - fitness costs
KW - incomplete resistance
KW - redundant killing
KW - resistance management
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U2 - 10.1002/ps.4746
DO - 10.1002/ps.4746
M3 - Article
C2 - 28967711
AN - SCOPUS:85041345903
SN - 1526-498X
VL - 74
SP - 627
EP - 637
JO - Pest Management Science
JF - Pest Management Science
IS - 3
ER -