Mechanism and DNA-based detection of field-evolved resistance to transgenic Bt corn in fall armyworm (Spodoptera frugiperda)

Abstract

Evolution of resistance threatens sustainability of transgenic crops producing insecticidal proteins from the bacterium Bacillus thuringiensis (Bt). The fall armyworm (Spodoptera frugiperda) is a devastating pest of corn in the Western Hemisphere initially controlled by transgenic Bt corn producing the Cry1Fa insecticidal protein (event TC1507). However field-evolved resistance to TC1507 was observed in Puerto Rico in 2007 and has subsequently been reported in a number of locations in North and South America. Early studies on Puerto Rico fall armyworm populations found that the resistance phenotype was associated with reduced expression of alkaline phosphatase. However, in this work we show that field-evolved resistance to Cry1Fa Bt corn in Puerto Rico is closely linked to a mutation in an ATP Binding Cassette subfamily C2 (ABCC2) gene that functions as a Cry1Fa receptor in susceptible insects. Furthermore, we report a DNA-based genotyping test used to demonstrate the presence of the resistant (SfABCC2mut) allele in Puerto Rico populations in 2007, coincident with the first reports of damage to TC1507 corn. These DNA-based field screening data provide strong evidence that resistance to TC1507 in fall armyworm maps to the SfABCC2 gene and provides a useful molecular marker for detecting the SfABCC2mut allele in resistant fall armyworm.

High-depth resequencing reveals hybrid population and insecticide resistance characteristics of fall armyworm (Spodoptera frugiperda) invading China

“…Mitochondrial COI and Tpi markers were used for strain identification. ABCC2, RyR, AChE genes were detected based on primers designed according to published mutation sites [31][32][33] . Mitochondrial insertion fragment detection was conducted using primers designed in this study.…”

“…The mechanisms of resistance to pesticides are mainly due to variation in receptor genes, such as amino acid mutations in the ryanodine receptor (RyR) (diamide), acetylcholinesterase (AChE) (organophosphate), voltagegated sodium channel (VGSC) (pyrethroids), and so on [30][31][32] . In addition, the frame-shift mutation resulting in early termination of the ABCC2 gene, caused by a 2-bp insertion, is linked to resistance to Cry1Fa 33 . Field-evolved strains resistant to Vip3Aa20 were obtained by screening homozygous resistance loci in F 2 generations in the laboratory 34 .…”

Diversity of fall armyworm, Spodoptera frugiperda and their gut bacterial community in Kenya

“…Further, the use of highly hazardous pesticides is not considered a sustainable long term control measure for any pest (FAO 2018). In addition, S. frugiperda is known to readily develop resistance to most chemical insecticides (e.g., pyrethroids, organophosphates and carbamates) and to transgenic maize that are used to control it (Yu 1991; Jakka et al 2016; Banerjee et al 2017; Flagel et al 2018; Botha et al 2019). In light of this, there is a great need for alternative, cost-effective control strategies for S. frugiperda (FAO 2018).…”

Dominant point mutation in a tetraspanin gene associated with field-evolved resistance of cotton bollworm to transgenic Bt cotton

“…Because such recessive resistance can be suppressed more readily, nonrecessive resistance is more likely to evolve in the field (8). Nonetheless, most research has focused on recessive resistance conferred by mutations that disrupt binding of Bt toxins in the larval midgut to receptors such as cadherin and ATP-binding cassette transporter proteins (12)(13)(14)(15)(16)(17), whereas little is known about the genetic basis of dominant resistance. Moreover, previous efforts to achieve proactive molecular monitoring of Bt resistance have had limited success because the mutations that increase markedly in the field are usually identified after resistance has caused severe control failures (13,14,16).…”