D3268: Targeted sequencing to screen for resistance to Cry proteins from Bacillus thuringiensis in the fall armyworm, Spodoptera frugiperda (J. E. Smith)

The fall armyworm (FAW,Spodoptera frugiperda) is a highly polyphagous pest native to tropical America which has spread globally, threatening food and fiber production. Transgenic crops producing insecticidal Cry and Vip3Aa proteins from the bacterium Bacillus thuringiensis (Bt) have been used for effective control in North and South America. Evolution of practical resistance to Bt crops represents the greatest threat to sustainability and its potential use in controlling FAW in its invasive range. Monitoring for resistance is vital to management approaches intended to delay resistance to Bt crops in FAW. DNA-based methods present high sensitivity and cost-effectiveness compared to current bioassay-based resistance monitoring. Here we discuss the use of targeted sequencing of the SfABCC2 gene, which is linked to practical resistance of FAW against Cry1F corn. This includes screening for known and candidate resistance alleles in field-collected FAW from the continental USA, Africa (Ghana, Togo and South Africa) and Southeast Asia (Myanmar). Genetic screening identified novel candidate resistance alleles and support the potential dispersal by migration. These results contribute to our understanding of FAW resistance to Bt corn and its spread, and supports further development of targeted sequencing for Bt resistance monitoring.