Frequency of Cry1F Non-Recessive Resistance Alleles in North Carolina Field Populations of Spodoptera frugiperda (Lepidoptera: Noctuidae)

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.

Characterization of field‐evolved resistance to Bacillus thuringiensis‐derived Cry1F δ‐endotoxin in Spodoptera frugiperda populations from Argentina

“…In the same study, < 2% resistance allele frequencies were estimated for Florida and Texas S. frugiperda populations. Recently, studies in the US found resistance in S. frugiperda populations from North Carolina , …”

Role of dispersal in resistance evolution and spread

“…On the other hand, recent susceptibility surveys suggest resistance in different areas of Florida may be of independent evolutionary origin [46,47]. Resistance alleles were detected at low frequency in North Carolina, which receives annual migrants from Florida [48]. Population genetic and atmospheric trajectory analyses have effectively ruled out a Caribbean origin of the Cry1F resistance found in Brazil [49 ].…”

Cross‐resistance to purified Bt proteins, Bt corn and Bt cotton in a Cry2Ab2‐corn resistant strain of Spodoptera frugiperda

“…Studies have shown that Cry1Ab and Cry1Ac are not highly effective for control of S. frugiperda . Additionally, S. frugiperda has already developed field resistance to Cry1F corn in Puerto Rico, Brazil, and the southeast region of the US mainland . Because of strong cross‐resistance among Cry1 proteins in Cry1F‐resistant S. frugiperda , none of the Cry1 proteins in the market is effective against S. frugiperda where Cry1F resistance is present.…”