Abstract
Fall armyworm, Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae), is a target species of transgenic corn (Zea mays L.) that expresses single and pyramided Bacillus thuringiensis (Bt) toxin. In 2014, S. frugiperda were collected from a light trap in North Carolina, and a total of 212 F1/F2 isofemale lines of S. frugiperda were screened for resistance to Bt and non-Bt corn. All of the 212 isolines were susceptible to corn tissue expressing Cry1A.105 + Cry2Ab, Cry1F + Cry1A.105 + Cry2Ab, and Cry1F + Cry1Ab + Vip3Aa20. Growth rate bioassays were performed to isolate non-recessive Bt resistance alleles. Seven individuals out of the 212 isofemale lines carried major non-recessive alleles conferring resistance to Cry1F. A pooled colony was created from the seven individuals. This colony was 151.21 times more resistant to Cry1F than a known-susceptible population and was also resistant to Cry1A.105, but was not resistant to Cry2Ab and Vip3Aa20. The results demonstrate that field populations of S. frugiperda collected from North Carolina are generally susceptible to Cry1F, but that some individuals carry resistant alleles. The data generated in this study can be used as baseline data for resistance monitoring.
Highlights
Corn, Zea mays (L.), expressing the Cry1F protein (Event TC1507, Herculex1 I insect protection technology by Dow AgroSciences and DuPont Pioneer) was first registered in the United States during 2001
Since resistance in North Carolina was detected during 2013 [5], we carried out experiments using the F1/F2 screening method that was proposed by Burd et al [27] to monitor the frequency of non-recessive resistance alleles and larval susceptibility of S. frugiperda to Bacillus thuringiensis (Bt) corn containing single or pyramided genes from eastern North Carolina, USA
We used the F1/F2 larvae of isofemale lines to test the frequency of non-recessive resistance alleles of S. frugiperda collected in North Carolina
Summary
Zea mays (L.), expressing the Cry1F protein (Event TC1507, Herculex I insect protection technology by Dow AgroSciences and DuPont Pioneer) was first registered in the United States during 2001. Burd et al [27] developed a bioassay to estimate the frequency of these major non-recessive resistance alleles using isofemale lines of F1/F2 generation. This method is appropriate when resistant alleles are not rare in the population. Since resistance in North Carolina was detected during 2013 [5], we carried out experiments using the F1/F2 screening method that was proposed by Burd et al [27] to monitor the frequency of non-recessive resistance alleles and larval susceptibility of S. frugiperda to Bt corn containing single or pyramided genes from eastern North Carolina, USA
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