Effective dominance of resistance of Spodoptera frugiperda to Bt maize and cotton varieties: implications for resistance management

Abstract

The resistance of fall armyworm (FAW), Spodoptera frugiperda, has been characterized to some Cry and Vip3A proteins of Bacillus thuringiensis (Bt) expressed in transgenic maize in Brazil. Here we evaluated the effective dominance of resistance based on the survival of neonates from selected Bt-resistant, heterozygous, and susceptible (Sus) strains of FAW on different Bt maize and cotton varieties. High survival of strains resistant to the Cry1F (HX-R), Cry1A.105/Cry2Ab (VT-R) and Cry1A.105/Cry2Ab/Cry1F (PW-R) proteins was detected on Herculex, YieldGard VT PRO and PowerCore maize. Our Vip3A-resistant strain (Vip-R) exhibited high survival on Herculex, Agrisure Viptera and Agrisure Viptera 3 maize. However, the heterozygous from HX-R × Sus, VT-R × Sus, PW-R × Sus and Vip-R × Sus had complete mortality on YieldGard VT PRO, PowerCore, Agrisure Viptera, and Agrisure Viptera 3, whereas the HX-R × Sus and Vip-R × Sus strains survived on Herculex maize. On Bt cotton, the HX-R, VT-R and PW-R strains exhibited high survival on Bollgard II. All resistant strains survived on WideStrike, but only PW-R and Vip-R × Sus survived on TwinLink. Our study provides useful data to aid in the understanding of the effectiveness of the refuge strategy for Insect Resistance Management of Bt plants.

Managing fall armyworm, Spodoptera frugiperda (Lepidoptera: Noctuidae), with Bt maize and insecticides in southern Brazil

“…The damage by FAW of Bt maize plants during the late planting season could also be a consequence of both selection pressure and low adoption of refuge areas for resistance management during the early planting season, which could increase the frequency of resistant individuals and, consequently, damage to maize plants that express pyramided Cry1 proteins. This hypothesis is supported by the presence of cross‐resistance among Cry1 proteins that are expressed in maize, have high similarity in amino acid sequence and use the same binding sites in the midgut of FAW . Even with the expression of the Cry2Ab2 protein in some pyramided maize plants, its toxicity is not enough to kill FAW larvae that are resistant to Cry1 proteins.…”

“…This hypothesis is supported by the presence of cross-resistance among Cry1 proteins that are expressed in maize, have high similarity in amino acid sequence and use the same binding sites in the midgut of FAW. 15,17,31,33,34 Even with the expression of the Cry2Ab2 protein in some pyramided maize plants, its toxicity is not enough to kill FAW larvae that are resistant to Cry1 proteins. Also, the expression of the Cry3Bb1 protein in YieldGard VT Pro 3 does not include FAW as a pest-control target.…”

Induction of resistance to fall armyworm (Spodoptera frugiperda) (Lepidoptera: Noctuidae) in transgenic and conventional corn plants

“…This decrease in the number of caterpillars in the conventional hybrid indicates plant resistance induction due to the application of a silicon source and suggests an alternative for S. frugiperda control and/or a control alternative in the refuge area in corn to disfavor the selection of pest resistance to Bt organisms (Zancanaro et al, 2012;Horkoshi et al, 2016).…”

“…The use of transgenic corn plants expressing Bacillus thuringiensis (Bt) insecticidal proteins is one of the main alternatives for fall armyworm control in Brazil, reaching 80% of the planted area ). In the current corn production system in Brazil, multiple cropping with some Bt crops and the non-implementation of refuge areas have contributed to the evolution of resistance to Bt corn plants in the fall armyworm population (Farias et al, 2014;Horkoshi et al, 2016). Fall armyworm resistance to the Cry1F Bt protein has already been reported in Brazil (Farias et al, 2014).…”

Geographical distribution of Vip3Aa20 resistance allele frequencies in Spodoptera frugiperda (Lepidoptera: Noctuidae) populations in Brazil

“…The vast majority of commercially released Bt events express proteins from the Cry1 group. Cry1 proteins show a high level of cross‐resistance to other Bt maize and cotton technologies . In addition, cross‐resistance among Cry2 proteins has recently been reported, and this group also occurs in Bt maize and cotton events in Brazil.…”