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23 May 2017 Magnitude and Allele Frequency of Cry1F Resistance in Field Populations of the Fall Armyworm (Lepidoptera: Noctuidae) in Brazil
O. F. Santos-Amaya, C. S. Tavares, J.V.C. Rodrigues, T. C. Souza, N. Rodrigues-Silva, R.N.C. Guedes, A. P. Alves, E.J.G. Pereira
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Abstract

Bacillus thuringiensis (Bt) corn producing the Cry1F protein was the first highly efficacious Bt corn deployed against the fall armyworm Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) in Brazil, but reduced efficacy of this technology against the fall armyworm has been reported in some regions of the country. Here, we surveyed Cry1F resistance allele frequency and susceptibility of eight S. frugiperda populations collected in 2013 from non-Bt fields in different regions of Brazil. In F1 screen experiments, the overall frequency of the Cry1F resistance alleles in Brazilian populations was estimated at 0.24, with 95% credibility interval between 0.18 and 0.25. In concentration–response bioassays, five of the eight populations surveyed exhibited significant resistance levels, which were over 32 times higher than that of the standard susceptible laboratory strain. The estimates of Cry1F resistance allele frequency were positively correlated with those of median effective or lethal concentrations (i.e., EC50 or LC50). These results show that the allelic frequency and the magnitude of Cry1F resistance are high in field populations of S. frugiperda in Brazil, indicating a challenging situation for resistance management.

© The Authors 2017. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com
O. F. Santos-Amaya, C. S. Tavares, J.V.C. Rodrigues, T. C. Souza, N. Rodrigues-Silva, R.N.C. Guedes, A. P. Alves, and E.J.G. Pereira "Magnitude and Allele Frequency of Cry1F Resistance in Field Populations of the Fall Armyworm (Lepidoptera: Noctuidae) in Brazil," Journal of Economic Entomology 110(4), 1770-1778, (23 May 2017). https://doi.org/10.1093/jee/tox146
Received: 15 December 2016; Accepted: 1 May 2017; Published: 23 May 2017
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