Pest Management Science (2016) 72, 2295-2302

Juliano R. Farias, David A. Andow, Renato J. Horikoshi, Daniel Bernardi, Rebeca da S. Ribeiro, Antonio R.B. do Nascimento, Antonio C. dos Santos and Celso Omoto (2016)
Frequency of Cry1F resistance alleles in Spodoptera frugiperda (Lepidoptera: Noctuidae) in Brazil
Pest Management Science 72 (12), 2295-2302
Abstract:
BACKGROUND
The frequency of resistance alleles is a major factor influencing the rate of resistance evolution. Here, we adapted the F₂ screen procedure for Spodoptera frugiperda (J. E. Smith) with a discriminating concentration assay, and extended associated statistical methods to estimate the frequency of resistance to Cry1F protein in S. frugiperda in Brazil when resistance was not rare.
RESULTS
We show that F₂ screen is efficient even when the resistance frequency is 0.250. It was possible to screen 517 isoparental lines from 12 populations sampled in five states of Brazil during the first half of 2012. Western Bahia had the highest allele frequency of Cry1F resistance, 0.192, with a 95% confidence interval (CI) between 0.163 and 0.220. All other states had a similar and lower frequency varying from 0.042 in Paraná to 0.080 in Mato Grosso do Sul.
CONCLUSION
The high frequency in western Bahia may be related to year-round availability of maize, the high population density of S. frugiperda, the lack of refuges and the high adoption rate of Cry1F maize. Cry1F resistance alleles were not rare and occurred at frequencies that have already compromised the useful life of TC1507 maize in western Bahia.
(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): Celso Omoto

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.
	Spodoptera frugiperda	Maize/corn (Zea mays)	Brazil (NE)
Bacillus thuringiensis Cry1F-toxin (entomopathogen)	Spodoptera frugiperda	Maize/corn (Zea mays)	Brazil (NE)