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

Abstract

BACKGROUND The use of Bt plants has been the main strategy for controlling the fall armyworm Spodoptera frugiperda (J. E. Smith) in Brazil. However, many resistance cases were already registered. The resistance of S. frugiperda to the Vip3Aa20 protein was recently characterized under laboratory conditions but it is still efficient under field conditions. Here, resistance monitoring studies were conducted using phenotypic (purified protein and Bt maize leaves) and genotypic (F1 and F2 screen) methods to support insect resistance management (IRM) programs and preserve Vip3Aa20 technology on maize. RESULTS Phenotypic monitoring with purified protein showed two populations significantly different from the susceptible strain on the second crop season in 2016. This number increased for the first and second crop seasons in 2017 in several regions. The genotypic monitoring estimated a mean frequency of the resistance allele of 0.0027 for the F1 screen and 0.0033 for the F2 screen. Three new resistant strains to Vip3Aa20 were selected from F2 screen assays. Complementation tests on these new resistant strains were positive with the previous resistant strain. CONCLUSION Here we showed that the resistance allele of S. frugiperda to Vip3Aa20 protein is widely distributed in maize‐producing regions in Brazil and its frequency increases throughout crop seasons. © 2019 Society of Chemical Industry

A new generation of Bt maize for control of fall armyworm (Spodoptera frugiperda)

“…Based on the limited efficacy of currently available Bt technologies expressing Cry1F, Cry1A.105, and/or Cry2Ab2 proteins to manage FAW, Vip3Aa20 is currently the most effective mode of action against FAW in the field in Brazil and Argentina. 40 , 41 The expression of Cry1B.868 and Cry1Da_7 in MON 95379 consistently protected maize plants against larval feeding of FAW over 2 years of field trials in locations in different geographic regions and environments across Brazil. These field trials were conducted in 2019 (season 2018/2019) and 2020 (season 2019/2020), and the sites represented most of the locations with widespread resistance to Cry1F maize.…”

“…This chain of events considerably reduces the choices that growers have to effectively manage FAW. Based on the limited efficacy of currently available Bt technologies expressing Cry1F, Cry1A.105, and/or Cry2Ab2 proteins to manage FAW, Vip3Aa20 is currently the most effective mode of action against FAW in the field in Brazil and Argentina 40,41 . The expression of Cry1B.868 and Cry1Da_7 in MON 95379 consistently protected maize plants against larval feeding of FAW over 2 years of field trials in locations in different geographic regions and environments across Brazil.…”

“…Vip3Aa20 is currently the most effective mode of action against FAW in the field in Brazil and Argentina. However, researchers were able to isolate a Vip3Aa20 resistance allele from a natural field population of the pest, indicating the potential for relatively rapid evolution of resistance in FAW under scenarios of low refuge compliance 40,41 . These circumstances indicate the need to identify new insecticidal modes of action and deploy them rapidly as pyramids with suitable refuge strategies to sustain the benefits of Bt maize to growers in South America 42 …”

Recombinant Phages for Spodoptera Frugiperda Control: New Perspectives to Tackle an Economic Problem

“…However, reports of insects' resistance to transgenic crops arose in 2006 in Puerto Rico [7][8][9] and in Brazil [10,11]. Recently the geographical distribution of S. frugiperda resistance was monitored providing important information for management programs [12,13]. In this context, it has become necessary to develop new effective products by the aid of innovative and biotechnological techniques.…”

Interação da toxina Cry1Ac de Bacillus thuringiensis às BBMVs de diferentes ínstares de Chrysodeixis includens (Lepidoptera: Noctuidae)

“…A evolução da resistência às toxinas Bt é uma realidade das culturas transgênicas (AMARAL, et al, 2019;CARRIERE et al, 2019. O mecanismo mais comum de resistente envolve mudanças nos sítios de ligação presentes no intestino médio das lagartas que, provavelmente reduzem a ligação às toxinas Bt (FABRICK; WU, 2015).…”