Resistance status of lepidopteran soybean pests following large-scale use of MON 87701 × MON 89788 soybean in Brazil

Abstract

Widespread adoption of MON 87701 × MON 89788 soybean, expressing Cry1Ac Bt protein and glyphosate tolerance, has been observed in Brazil. A proactive program was implemented to phenotypically and genotypically monitor Cry1Ac resistance in Chrysodeixis includens (Walker). Recent cases of unexpected injury in MON 87701 × MON 89788 soybean were investigated and a large-scale sampling of larvae on commercial soybean fields was performed to assess the efficacy of this technology and the distribution of lepidopteran pests in Brazil. No significant shift in C. includens susceptibility to Cry1Ac was observed eight years after commercial introduction of this technology in Brazil. F2 screen results confirmed that the frequency of Cry1Ac resistance alleles remains low and stable in C. includens. Unexpected injury caused by Rachiplusia nu (Guenée) and Crocidosema aporema (Walsingham) in MON 87701 × MON 89788 soybean was detected during the 2020/21 season, and studies confirmed a genetically based alteration in their susceptibility to Cry1Ac. MON 87701 × MON 89788 soybean remains effective against Anticarsia gemmatalis (Hübner), C. includens, Chloridea virescents (Fabricius) and Helicoverpa armigera (Hübner) in Brazil. However, there is evidence of field-evolved resistance to MON 87701 × MON 89788 soybean by the secondary soybean pests R. nu and C. aporema.

Practical resistance to Cry toxins and efficacy of Vip3Aa in Bt cotton against Helicoverpa zea

“…Practical resistance to a Bt crop is field‐evolved resistance that decreases the efficacy of the Bt crop and has practical consequences for pest control 8 . Practical resistance to Bt crystalline (Cry) toxins has been reported in some populations of at least 12 species of Lepidoptera and Coleoptera, including ten species that are pests of Bt crops 8–11 …”

“…8 Practical resistance to Bt crystalline (Cry) toxins has been reported in some populations of at least 12 species of Lepidoptera and Coleoptera, including ten species that are pests of Bt crops. [8][9][10][11] This article focuses on practical resistance to Cry toxins in Helicoverpa zea (also known as bollworm and corn earworm), one of the most economically important pests of cotton and other crops in the United States. 3,12,13 Many previous studies have documented widespread H. zea resistance to Cry toxins in the United States.…”

“…In 2019, farmers in 27 countries cultivated over 100 million hectares of Bt crops 5 . However, the benefits of these transgenic crops are reduced when pests evolve resistance 6–11 . Field‐evolved resistance to a Bt toxin is a genetically based decrease in susceptibility of an insect population to that toxin caused by selection in the field 8 .…”

“…5 However, the benefits of these transgenic crops are reduced when pests evolve resistance. [6][7][8][9][10][11] Field-evolved resistance to a Bt toxin is a genetically based decrease in susceptibility of an insect population to that toxin caused by selection in the field. 8 Practical resistance to a Bt crop is field-evolved resistance that decreases the efficacy of the Bt crop and has practical consequences for pest control.…”

Characterizing the lethal and sub‐lethal effects of genetically modified soybean expressing Cry1A.105, Cry2Ab2, and Cry1Ac insecticidal proteins against Spodoptera species (Lepidoptera: Noctuidae) in Brazil

“…Both Cry1Ac and Cry1A.105/Cry2Ab2/Cry1Ac soybean are effective against the primary lepidopteran pests that attack soybean in Brazil and other South American countries: Anticarsia gemmatalis (Hübner, 1818) (Lepidoptera: Erebidae), Chrysodeixis includens (Walker, [1858]), Chloridea virescens (Fabricius, 1781), and Helicoverpa armigera (Hübner, 1808) (Lepidoptera: Noctuidae). [3][4][5][6][7][8] However, the Cry1Ac soybean does not provide protection against Spodoptera species found in Brazil. 9 Species of genus Spodoptera are commonly observed in soybean fields in Brazil.…”