Assessing fitness costs of the resistance of Spodoptera frugiperda (Lepidoptera: Noctuidae) to pyramided Cry1 and Cry2 insecticidal proteins on different host plants

Abstract

Fall armyworm (FAW), Spodoptera frugiperda (Smith), is one of the major pests targeted by transgenic crops expressing insecticidal proteins from Bacillus thuringiensis (Bt) Berliner. However, FAW presents a high capacity to develop resistance to Bt protein-expressing crop lines, as reported in Brazil, Argentina, Puerto Rico and the southeastern U.S. Here, FAW genotypes resistant to pyramided maize events expressing Cry1F/Cry1A.105/Cry2Ab2 (P-R genotype) and Cry1A.105/Cry2Ab2 (Y-R genotype) from Brazil were used to investigate the interactions between non-Bt hosts (non-Bt maize, non-Bt cotton, millet and sorghum) and fitness costs. We also tested a FAW genotype susceptible to Bt maize and F1 hybrids of the resistant and susceptible genotypes (heterozygotes). Recessive fitness costs (i.e., costs affecting the resistant insects) were observed for pupal and neonate to adult survival of the P-R genotype on non-Bt cotton; larval developmental time of the P-R genotype on millet and sorghum; larval and neonate-to-adult developmental time of the Y-R genotype on non-Bt cotton and sorghum; the fecundity of the Y-R genotype on non-Bt cotton; and mean generation time of both resistant genotypes. However, on non-Bt cotton and non-Bt maize, the P-R genotype had a higher fitness (i.e., fitness benefits), displaying greater fecundity and rates of population increases than the Sus genotype. Non-recessive fitness costs (i.e., costs affecting heterozygotes) were found for fecundity and population increases on millet and sorghum. These findings suggest that, regardless of the disadvantages of the resistant genotypes in some hosts, the resistance of FAW to Cry1 and Cry2 Bt proteins is not linked with substantial fitness costs, and may persist in field conditions once present.

A soybean trypsin inhibitor reduces the resistance to transgenic maize in a population of Spodoptera frugiperda (Lepidoptera: Noctuidae)

“…The population susceptible to Bt maize (30A37PW, MON89034 × TC1507 × NK603, expression of Cry1F, Cry1A.105, and Cry2Ab2 Bt proteins) was maintained in laboratory without exposure to pesticides or transgenic plants for at least 15 years. The population resistant to Bt maize was kindly provided by Prof. Oderlei Bernardi from the Universidade Federal de Santa Maria-RS, Brazil corresponding to the F 29 generation of the resistant population ( Bernardi et al 2017 , Garlet et al 2022 ). This resistant population was kept under selection pressure since F 1 by feeding larvae Bt maize at least each 2 generations.…”

A Social Network Analysis approach for identifying critical research areas in the management of Fall armyworm (Spodoptera frugiperda)

“…According to recent research, S. frugiperda caterpillars are sensitive to both biotic and abiotic stimuli, as revealed in the vibroscape study (Turchen et al, 2022). However, there has been a gradual increase in resistance to Emamectin benzoate over the last few years (Garlet et al, 2022;Muraro et al, 2022), and susceptibility to various insecticides has also varied regarding the evolution of FAW resistance. A recent study has identi ed the potential insecticidal effects of compounds such as N, Ndimethylaniline and 1,2,5-trithiepane on S. frugiperda caterpillars (Campos et al, 2022).…”

“…al., 2022; Nhim et al, 2022; Okuma et al, 2022; L. Zhang et al, 2020).Discovery and expression of insecticidal protein genes from Bt in transgenic crops is a popular research area(100-200 frequency). Bt T405 has been found to combined Cry1, Cry2Aa, Cry2Ab, and vip3A1, in addition to a wide range of FAW-susceptible toxins (Cry) and proteins (vegetative insecticidal proteins)(Schnable et al, 2009; Barcellos et al, 2023;Garlet et al, 2022;Hernández-Martínez et al, 2013). Sathyan et al (2022) discovered protein-coding genes for potential FAW insecticidal toxins, including Cry1Ac32, Cry1Ab9, Cry1Aa6, Cry1Ac5, Cry1Aal8, Cry1Ab8, Cry1Ab11, Cry2Aa9, Cry1Ia40, Cry2Ab35, Cyt, Vip3Aa7, and tpp80Aa, as well as genes that may enhance virulence such as phospholipase C, chitinase, immune inhibitor A, cell wall hydrolases, sphingomyelinase, hemolysin Xh1A, and urease subunit coding genes.Delanthabettu et al (2022) identi ed several genes, including Cry1I, Cry3, Cry7, Cry8, Cry14, Cry26, and Cry55, across 12 different natural Bt strains.…”