Shared genetic basis of resistance to Cry1F protein in three independent Brazilian strains of fall armyworm

Field strains of the fall armyworm (FAW), Spodoptera frugiperda (Lepidoptera: Noctuidae), a global pest of corn, have evolved practical resistance to transgenic corn-producing the Bt protein Cry1F in Brazil, Argentina, and the United States. Considering the rapid invasion of FAW and the worldwide adoption of Bt crops for its control, it is important to understand the genetic basis of resistance to Cry1F in resistant strains of FAW from different regions of the world. This information is essential for developing new transgenic Bt crops and designing appropriate strategies for resistance management for FAW in Bt crops. Thus, the objective of this work was to determine whether Brazilian strains of FAW from different geographic origins share the same locus of resistance to Cry1F. We conducted interstrain complementation tests for allelism among three resistant strains. The survival of F1 progenies from crosses among FAW-resistant strains in purified Cry1F protein or Cry1F-corn was similar to that observed for the parental strains. Our results suggest that mutations conferring resistance to Cry1F Bt protein in three strains of FAW are present in a single locus. Results from this study provide information for developing effective strategies for Bt resistance management, which is the main limitation for sustainable use of Bt technology against this pest.

Automated summary

Field strains of fall armyworm have developed resistance to Bt protein Cry1F in Brazil, Argentina, and the United States. This study found that mutations conferring resistance to Cry1F in three strains of fall armyworm are present in a single locus, providing valuable information for developing effective strategies for Bt resistance management.