Cross-crop resistance of Spodoptera frugiperda selected on Bt maize to genetically-modified soybean expressing Cry1Ac and Cry1F proteins in Brazil

Eduardo P Machado,Oderlei Bernardi,Gerson L Dos S Rodrigues Junior,Mark L Dahmer,Timothy Nowatzki,Stefan L Zago,Fábio M Führ,Luiz H Marques,Celso Omoto,Antonio C Santos

doi:10.1038/s41598-020-67339-1

Abstract

Spodoptera frugiperda is one of the main pests of maize and cotton in Brazil and has increased its occurrence on soybean. Field-evolved resistance of this species to Cry1 Bacillus thuringiensis (Bt) proteins expressed in maize has been characterized in Brazil, Argentina, Puerto Rico and southeastern U.S. Here, we conducted studies to evaluate the survival and development of S. frugiperda strains that are susceptible, selected for resistance to Bt-maize single (Cry1F) or pyramided (Cry1F/Cry1A.105/Cry2Ab2) events and F1 hybrids of the selected and susceptible strains (heterozygotes) on DAS-444Ø6-6 × DAS-81419-2 soybean with tolerance to 2,4-d, glyphosate and ammonium glufosinate herbicides (event DAS-444Ø6-6) and insect-resistant due to expression of Cry1Ac and Cry1F Bt proteins (event DAS-81419-2). Susceptible insects of S. frugiperda did not survive on Cry1Ac/Cry1F-soybean. However, homozygous-resistant and heterozygous insects were able to survive and emerge as fertile adults when fed on Cry1Ac/Cry1F-soybean, suggesting that the resistance is partially recessive. Life history studies revealed that homozygous-resistant insects had similar development, reproductive performance, net reproductive rate, intrinsic and finite rates of population increase on Cry1Ac/Cry1F-soybean and non-Bt soybean. In contrast, heterozygotes had their fertility life table parameters significantly reduced on Cry1Ac/Cry1F-soybean. Therefore, the selection of S. frugiperda for resistance to single and pyramided Bt maize can result in cross-crop resistance to DAS-444Ø6-6 × DAS-81419-2 soybean. The importance of these results to integrated pest management (IPM) and insect resistance management (IRM) programs is discussed.

Highlights

Transgenic plants expressing insecticidal proteins from Bacillus thuringiensis Berliner (Bt) have significantly contributed to integrated pest management (IPM) programs worldwide in the last decades[1,2,3,4]
The dominance levels (DML) of resistance of S. frugiperda on Cry1Ac/ Cry1F-soybean were 0.32 and 0.40 for P-R and H-R strains, respectively, indicating that the resistance is partially recessive
The colonies of S. frugiperda selected for resistance to single- and pyramided-Bt maize technologies showed high survival on Cry1Ac/Cry1F-soybean

Summary

Introduction

Transgenic plants expressing insecticidal proteins from Bacillus thuringiensis Berliner (Bt) have significantly contributed to IPM programs worldwide in the last decades[1,2,3,4]. The DAS-81419-2 event (Conkesta, Corteva Agriscience, Wilmington, DE) consists of insect-resistant technology that expresses Cry1Ac and Cry1F Bt proteins[11,12], and PAT that confers tolerance to the herbicide glufosinate ammonium as a selectable marker Under field conditions, this Bt soybean provides protection against A. gemmatalis, C. includens, C. virescens and H. armigera[13,14]. In Brazilian soybean fields there has been an increase in the occurrence of Spodoptera species, mainly Spodoptera frugiperda (Lepidoptera: Noctuidae)15–17—one the main lepidopteran pest of maize (Zea mays L.) and cotton (Gossypium hirsutum L.)[18,19] Their occurrence in soybean can be explained by their ability to develop in several cultivated plants[20,21], adult dispersal[22], reproductive capacity, multiple generations per year[23] and the Brazilian crop production system where there is an overlap of cultivated host plants (i.e. maize, cotton, sorghum, rice and soybean)[24]. These biological characteristics associated with the crop production landscapes favors the infestation of this pest on distinct cultivated host plants throughout the seasons

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Results

Conclusion