Frequency of Vip3Aa20 resistance allele using F1 screen in field populations of Spodoptera frugiperda in Brazil

The initial frequency of resistance allele is one of the factors affecting the evolution of pest resistance to pesticides. In this study, we estimated the Vip3Aa20 allele frequency in Brazilian populations of Spodoptera frugiperda collected in 2015. After selecting S. frugiperda strain resistant to Vip3Aa20 (Vip-R), we used F₁ screen method to estimate the frequency of Vip3Aa20 resistance allele in field-populations of S. frugiperda collected from seven Brazilian states, pairing field-collected insects with Vip-R strain ones. F₁ neonates were exposed to excised-corn leaf tissue expressing Vip3Aa20 protein. Vip-R strain share the same resistance allele locus with individuals from different states. Our findings also indicate that Vip3Aa20 resistance allele frequency is still very low.  Therefore, if other factors such recessive inheritance of resistance and high refuge compliance are met, the risk of resistance to Vip3Aa20 in S. frugiperda can be minimized.