Estimating the frequency of Cry1F resistance in field populations of the European corn borer (Lepidoptera: Crambidae)

Authors

Blair D. Siegfried, University of Nebraska-LincolnFollow
Murugesan Rangasamy, University of Nebraska-Lincoln
Haichuan Wang, University of Nebraska-Lincoln
Terence Spencer, University of Nebraska-Lincoln
Chirakkal V. Haridas, University of Nebraska-Lincoln
Brigitte Tenhumberg, University of Nebraska-LincolnFollow
Douglas V. Sumerford, Iowa State University
Nicholas P. Storer, Dow AgroSciences

Document Type

Article

Date of this Version

2013

Citation

Pest Manag Sci 2014; 70: 725–733; DOI: 10.1002/ps.3662

Comments

Copyright © 2013 Society of Chemical Industry.

U.S. Government Work

Abstract

BACKGROUND: Transgenic corn hybrids that express toxins from Bacillus thuringiensis (Bt) have suppressed European corn borer populations and reduced the pest status of this insect throughout much of the US corn belt. A major assumption of the high-dose/refuge strategy proposed for insect resistancemanagement and Bt corn is that the frequency of resistance alleles is low so that resistant pests surviving exposure to Bt corn will be rare.

RESULTS: The frequency of resistance to the Cry1F Bt toxin was estimated using twodifferent screening tools andcompared with annual susceptibility monitoring based on diagnostic bioassays and LC₅₀ and EC₅₀ determinations. An F₁ screening approach where field-collected individuals were mated to a resistant laboratory strain and progeny were assayed to determine genotype revealed that resistance alleles could be recovered even during the first year of commercially available Cry1F corn (2003). Estimates of frequency from 2003–2005 and 2006–2008 indicated that, although allele frequency was higher than theoretical assumptions (0.0286 and 0.0253 respectively), there was no indication that the frequency was increasing. Similar estimates in 2008 and 2009 using an F₂ screening approach confirmed the presence of non-rare resistance alleles (frequency≈0.0093 and 0.0142 for 2008 and 2009, respectively). The results of both screening methods were in general agreement with the observed mortality in diagnostic bioassays and LC₅₀ and EC₅₀ determinations.

CONCLUSIONS: These results are consistent with previous modeling results, suggesting that the high-dose/refuge strategy that is in place for Bt corn may be effective in delaying resistance evolution even when a relatively high frequency of resistance alleles exists.