ABCtransporter mutations inCry1F-resistant fall armyworm (Spodoptera frugiperda) do not result in altered susceptibility to selected small molecule pesticides

BACKGROUND Transgenic crops producing Cry and Vip3 insecticidal proteins from the bacteriumBacillus thuringiensisprovide effective control of the fall armyworm,Spodoptera frugiperdaJ. E. Smith. However, cases of practicalS. frugiperdaresistance to transgenic corn producing Cry1F, Cry1Ab and Cry1A.105 proteins have been reported in the Western hemisphere. Importantly,S. frugiperdaresistance to Cry1F corn in Puerto Rico was previously associated with lower susceptibility to synthetic pesticides. When characterized, resistance to transgenic corn inS. frugiperdainvolved alterations in an ABC transporter subfamily C2 (SfABCC2) gene. The main goal of this work was to test the role of mutations inSfABCC2that result in resistance to Cry1F in susceptibility to synthetic and semisynthetic small molecule pesticides. RESULTS Marginal but significantly reduced susceptibility to bifenthrin and increased susceptibility to spinetoram was detected in a Cry1F-resitantS. frugiperdastrain from Puerto Rico carrying a frameshift mutation in theSfABCC2gene. Gene editing by CRISPR/Cas9 created aSfABCC2knockout in a laboratory referenceS. frugiperdastrain. When compared to the parental reference, the knockout strain displayed 25-fold resistance to Cry1F but no alteration in susceptibility to small molecule pesticides. CONCLUSION These results support that resistance to Cry1F due to mutations in theSfABCC2gene do not affect susceptibility to the tested small molecule pesticides.

Automated summary

The study found that mutations in the SfABCC2 gene lead to resistance to Cry1F in fall armyworm, but do not affect susceptibility to synthetic small molecule pesticides.