Functional Importance of Deletion Mutant Genotypes in an Insect Nucleopolyhedrovirus Population

A Nicaraguan isolate of a nucleopolyhedrovirus (SfNIC) that attacks the fall armyworm, Spodoptera frugiperda, survives as a mixture of nine genotypes (SfNIC A to I) that all present genomic deletions, except variant B (complete genotype). Sequencing of cloned restriction fragments revealed that genotypic variants lack between 5 and 16 of the open reading frames present in a contiguous sequence of 18 kb of the SfNIC genome. The absence of oral infectivity of SfNIC-C and -D variants is related to the deletion of the pif and/or pif-2 gene, while that of SfNIC-G remains unexplained. The presence of open reading frame 10, homolog of Se030, also appeared to influence pathogenicity in certain variants. Previous studies demonstrated a significant positive interaction between genotypes B and C. We compared the median lethal concentration of single genotypes (A, B, C, D, and F) and co-occluded genotype mixtures (B+A, B+D, B+F, A+C, and F+C in a 3:1 ratio). Mixtures B+A and B+D showed increased pathogenicity, although only B+D restored the activity of the mixture to that of the natural population. Mixtures of two deletion variants (A+C and F+C) did not show interactions in pathogenicity. We conclude that minority genotypes have an important influence on the overall pathogenicity of the population. These results clearly demonstrate the value of retaining genotypic diversity in virus-based bioinsecticides.     

Deletion Genotypes Reduce Occlusion Body Potency but Increase Occlusion Body Production in a Colombian Spodoptera frugiperda Nucleopolyhedrovirus Population

A Colombian field isolate (SfCOL-wt) of Spodoptera frugiperda multiple nucleopolyhedrovirus (SfMNPV) is a mixture of different genotypes. To evaluate the insecticidal properties of the different genotypic variants, 83 plaque purified virus were characterized. Ten distinct genotypes were identified (named A through J). SfCOL-A was the most prevalent (71±2%; mean ± SE) showing a PstI restriction profile indistinguishable to that of SfCOL-wt. The remaining nine genotypes presented genomic deletions of 3.8 - 21.8 Kb located mainly between nucleotides 11,436 and 33,883 in the reference genome SfMNPV-B, affecting the region between open reading frames (ORFs) sf20 and sf33. The insecticidal activity of each genotype from SfCOL-wt and several mixtures of genotypes was compared to that of SfCOL-wt. The potency of SfCOL-A occlusion bodies (OBs) was 4.4-fold higher than SfCOL-wt OBs, whereas the speed of kill of SfCOL-A was similar to that of SfCOL-wt. Deletion genotype OBs were similarly or less potent than SfCOL-wt but six deletion genotypes were faster killing than SfCOL-wt. The potency of genotype mixtures co-occluded within OBs were consistently reduced in two-genotype mixtures involving equal proportions of SfCOL-A and one of three deletion genotypes (SfCOL-C, -D or -F). Speed of kill and OB production were improved only when the certain genotype mixtures were co-occluded, although OB production was higher in the SfCOL-wt isolate than in any of the component genotypes, or mixtures thereof. Deleted genotypes reduced OB potency but increased OB production of the SfCOL-wt population, which is structured to maximize the production of OBs in each infected host.     

Functional importance of deletion mutant genotypes in an insect nucleopolyhedrovirus population

A Nicaraguan isolate of a nucleopolyhedrovirus (SfNIC) that attacks the fall armyworm, Spodoptera frugiperda, survives as a mixture of nine genotypes (SfNIC A to I) that all present genomic deletions, except variant B (complete genotype). Sequencing of cloned restriction fragments revealed that genotypic variants lack between 5 and 16 of the open reading frames present in a contiguous sequence of 18 kb of the SfNIC genome. The absence of oral infectivity of SfNIC-C and -D variants is related to the deletion of the pif and/or pif-2 gene, while that of SfNIC-G remains unexplained. The presence of open reading frame 10, homolog of Se030, also appeared to influence pathogenicity in certain variants. Previous studies demonstrated a significant positive interaction between genotypes B and C. We compared the median lethal concentration of single genotypes (A, B, C, D, and F) and co-occluded genotype mixtures (B+A, B+D, B+F, A+C, and F+C in a 3:1 ratio). Mixtures B+A and B+D showed increased pathogenicity, although only B+D restored the activity of the mixture to that of the natural population. Mixtures of two deletion variants (A+C and F+C) did not show interactions in pathogenicity. We conclude that minority genotypes have an important influence on the overall pathogenicity of the population. These results clearly demonstrate the value of retaining genotypic diversity in virus-based bioinsecticides.     

Mixed genotype transmission bodies and virions contribute to the maintenance of diversity in an insect virus

An insect nucleopolyhedrovirus naturally survives as a mixture of at least nine genotypes. Infection by multiple genotypes results in the production of virus occlusion bodies (OBs) with greater pathogenicity than those of any genotype alone. We tested the hypothesis that each OB contains a genotypically diverse population of virions. Few insects died following inoculation with an experimental two-genotype mixture at a dose of one OB per insect, but a high proportion of multiple infections were observed (50%), which differed significantly from the frequencies predicted by a non-associated transmission model in which genotypes are segregated into distinct OBs. By contrast, insects that consumed multiple OBs experienced higher mortality and infection frequencies did not differ significantly from those of the non-associated model. Inoculation with genotypically complex wild-type OBs indicated that genotypes tend to be transmitted in association, rather than as independent entities, irrespective of dose. To examine the hypothesis that virions may themselves be genotypically heterogeneous, cell culture plaques derived from individual virions were analysed to reveal that one-third of virions was of mixed genotype, irrespective of the genotypic composition of the OBs. We conclude that co-occlusion of genotypically distinct virions in each OB is an adaptive mechanism that favours the maintenance of virus diversity during insect-to-insect transmission.     

Entry into midgut epithelial cells is a key step in the selection of genotypes in a nucleopolyhedrovirus

An isolate of the Spodoptera frugiperda multiple nucleopolyhedrovirus comprises a stable proportion of deletion genotypes (e.g., SfNIC-C), that lack pif1 and pif2 rendering them noninfectious per os, and that survive by complementation with a complete genotype (SfNIC-B) in coinfected cells. To determine whether selection for particular ratios of complete and deletion genotypes occurs mainly during the establishment of the primary infection in insect midgut cells or during subsequent systemic infection, we examined genotype frequencies in insects that fed on OBs comprising different co-occluded mixtures of genotypes. Dramatic changes in genotype frequencies were observed between the OB inoculum and budded virus (BV) samples taken from larvae inoculated with OBs comprising 10% SfNIC-B + 90% SfNIC-C indicating that a marked reduction of SfNIC-C genotype had occurred in the insect midgut due to the immediate elimination of all OBs that originated from cells that had been infected only by SfNIC-C. In contrast, immediate changes were not observed in OBs comprising mixtures of 50% SfNIC-B + 50% SfNIC-C or those comprising 10% SfNIC-B + 90% SfNIC-C as most of the OBs in these mixtures originated from cells that had been infected by both genotypes. Subsequent changes in genotypic frequencies during five days of systemic infection were fairly small in magnitude for all genotypic mixtures. We conclude that the prevalence of defective genotypes in the SfNIC population is likely determined by a balance between host selection against OBs produced in cells infected by SfNIC-C alone and within-host selection for fast-replicating deletion genotypes. The strength of intra-host selection is likely modulated by changes in MOI during the infection period.     

Phenotypic characteristics and relative proportions of three genotypic variants isolated from a nucleopolyhedrovirus of Spodoptera exigua

US2A, US2D, and US2F are three in vivocloned genotypic variants from the wild-type strain of a Spodoptera exiguanucleopolyhedrovirus (SeMNPV) isolated in Florida (USA) and is the active component of the commercial bioinsecticide Spod-X^®. These variants were compared in terms of pathogenicity (LD₅₀), speed of kill (expressed as mean time to death) and viral progeny productivity (OBs/larva). LD₅₀values were similar for the three cloned genotypes. The mean time to death value for US2D (113.7 h) was significantly higher than those of US2A (31.7 h) and US2F (27.8 h). Virus yield was determined for L₄larvae infected with the estimated LD₉₉. US2D infected larvae attained higher weight than those infected with US2A and US2F, and produced a higher OB yield than larvae infected with US2A or US2F. An outstanding feature of US2F, in contrast to US2A and US2D, was its inability to disrupt the teguments of NPV-killed larvae. To study the relative proportion of the three genotypic variants throughout successive passages, S. exigualarvae were originally infected with a viral inoculum containing a 1:1:1 mixture of the three genotypes. After three successive passages, US2D was no longer detected in either of the three replicate experiments performed, while US2A was the predominant genotype in all of them, and US2F remained at similar proportions throughout the three passages. The influence of the phenotypic characteristics of the three variants on their relative proportions in mixed infections is discussed.     

Fitness costs of Cry1F resistance in fall armyworm,Spodoptera frugiperda

Transgenic corn, Zea mays L., expressing the Bacillus thuringiensis Berliner (Bt) protein Cry1F has been registered for Spodoptera frugiperda (J. E. Smith) control since 2003 in the USA. Unexpected damage to Cry1F corn was reported in 2006 in Puerto Rico, and Cry1F resistance in S. frugiperda from Puerto Rico was documented. The study of fitness costs associated with insect resistance to Bt insecticidal proteins is important for understanding resistance evolution and for evaluating resistance management practices used to mitigate resistance to transgenic corn. Currently, no studies have addressed the fitness costs associated with Cry1F resistance in S. frugiperda. In this study, susceptible and resistant strains with similar genetic background and their reciprocal crosses were used to estimate Cry1F resistance fitness costs. Comparisons between life‐history traits and population growth rates of homozygous susceptible, heterozygous and homozygous resistant S. frugiperda were used to determine whether the resistance is associated with fitness costs. Major fitness costs were not apparent in either heterozygotes or homozygous resistant insects. However, there was a slight indication of hybrid vigour in the heterozygotes. Additionally, two lines in which the frequency of the resistant alleles was fixed at 0.5 were followed for seven generations, after which the frequency of resistant alleles slightly decreased in both lines. The lack of strong fitness costs associated with Cry1F resistance in S. frugiperda indicates that initial allele frequencies may be higher than expected in field populations and will tend to remain stable in field populations in the absence of selection pressure (e.g. Puerto Rico).     

Competition between wild-type and a marked recombinant baculovirus (Spodoptera exigua nucleopolyhedrovirus) with enhanced speed of action in insect larvae

Competition between virus genotypes in insect hosts is a key element of virus fitness, affecting their long-term persistence in agro-ecosystems. Little information is available on virus competition in insect hosts or during serial passages from one cohort of hosts to the next. Here we report on the competition between two genotypes of Spodoptera exigua nucleopolyhedrovirus (SeMNPV), when serially passaged as mixtures in cohorts of 4th instar S. exigua larvae. One of the genotypes was a SeMNPV wild-type isolate, SeUS1, while the other was a SeMNPV recombinant (SeMNPV-XD1) having a greater speed of kill than SeUS1. SeXD1 lacks a suite of genes, including the ecdysteroid UDP-glucosyl transferase (egt) gene. SeXD1 expresses the green fluorescent protein (GFP) gene, enabling the identification of SeXD1 in cell culture and in insects. The relative proportion of SeUS1 and SeXD1 in successive passages of mixed infections in various ratios was determined by plaque assays of budded virus from infected larvae and by polymerase chain reactions and restriction enzyme analyses. The SeUS1 genotype outcompeted recombinant SeXD1 over successive passages. Depending on the initial virus genotype ratio, the recombinant SeXD1 was no longer detected after 6-12 passages. A mathematical model was developed to characterize the competition dynamics. Overall, the ratio SeUS1/XD1 increased by a factor 1.9 per passage. The findings suggest that under the experimental conditions recombinant SeXD1 is displaced by the wild-type strain SeUS1, but further studies are needed to ascertain that this is also the case when the same baculoviruses would be used in agro-ecosystems.     

A Chrysodeixis chalcites Single-Nucleocapsid Nucleopolyhedrovirus Population from the Canary Islands Is Genotypically Structured To Maximize Survival

A Chrysodeixis chalcites single-nucleocapsid nucleopolyhedrovirus wild-type isolate from the Canary Islands, Spain, named ChchSNPV-TF1 (ChchTF1-wt), appears to have great potential as the basis for a biological insecticide for control of the pest. An improved understanding of the genotypic structure of this wild-type strain population should facilitate the selection of genotypes for inclusion in a bioinsecticidal product. Eight genetically distinct genotypes were cloned in vitro: ChchTF1-A to ChchTF1-H. Quantitative real-time PCR (qPCR) analysis confirmed that ChchTF1-A accounted for 36% of the genotypes in the wild-type population. In bioassays, ChchTF1-wt occlusion bodies (OBs) were significantly more pathogenic than any of the component single-genotype OBs, indicating that genotype interactions were likely responsible for the pathogenicity phenotype of wild-type OBs. However, the wild-type population was slower killing and produced higher OB yields than any of the single genotypes alone. These results strongly suggested that the ChchTF1-wt population is structured to maximize its transmission efficiency. Experimental OB mixtures and cooccluded genotype mixtures containing the most abundant and the rarest genotypes, at frequencies similar to those at which they were isolated, revealed a mutualistic interaction that restored the pathogenicity of OBs. In OB and cooccluded mixtures containing only the most abundant genotypes, ChchTF1-ABC, OB pathogenicity was even greater than that of wild-type OBs. The ChchTF1-ABC cooccluded mixture killed larvae 33 h faster than the wild-type population and remained genotypically and biologically stable throughout five successive passages in vivo. In conclusion, the ChchTF1-ABC mixture shows great potential as the active ingredient of a bioinsecticide to control C. chalcites in the Canary Islands.     

Genotypic and phenotypic diversity of a baculovirus population within an individual insect host

It is becoming increasingly apparent that many pathogen populations, including those of insects, show high levels of genotypic variation. Baculoviruses are known to be highly variable, with isolates collected from the same species in different geographical locations frequently showing genetic variation and differences in their biology. More recent studies at smaller scales have also shown that virus DNA profiles from individual larvae can show polymorphisms within and between populations of the same species. Here, we investigate the genotypic and phenotypic variation of an insect baculovirus infection within a single insect host. Twenty four genotypically distinct nucleopolyhedrovirus (NPV) variants were isolated from an individual pine beauty moth, Panolis flammea, caterpillar by in vivo cloning techniques. No variant appeared to be dominant in the population. The PaflNPV variants have been mapped using three restriction endonucleases and shown to contain three hypervariable regions containing insertions of 70-750 bp. Comparison of seven of these variants in an alternative host, Mamestra brassicae, demonstrated that the variants differed significantly in both pathogenicity and speed of kill. The generation and maintenance of pathogen heterogeneity are discussed.     

The relative influences of host plant genotype and yearly abiotic variability in determining herbivore abundance

Both plant genotype and yearly abiotic variation affect herbivore population sizes, but long-term data have rarely been used to contrast the relative contributions of each. Using a hierarchical Bayesian model, we directly compare effects of these two factors on the population size of a common herbivore, Aceria parapopuli, on Populus angustifolia × fremontii F₁ hybrid trees growing in a common garden across 8 years. Several patterns emerged. First, the Bayesian posterior estimates of tree genotype effects on mite gall number ranged from 0.0043 to 229 on a linear scale. Second, year effect sizes across 8 years of study ranged from 0.133 to 1.895. Third, in comparing the magnitudes of genotypic versus yearly variation, we found that genotypic variation was over 130 times greater than variation among years. Fourth, precipitation in the previous year negatively affected gall abundances, but was minimal compared to tree genotype effects. These findings demonstrate the relative importance of tree genotypic variation in determining herbivore population size. However, given the demonstrated sensitivity of cottonwoods to drought, the loss of individual tree genotypes from an altered climate would have catastrophic impacts on mites that are dependent upon these genotypes for their survival.     

Agroforestry coffee soils increase the insect‐suppressive potential offered by entomopathogenic fungi over full‐sun soils: A case proposing a “bait survival technique”

Entomopathogenic fungi are important natural enemies of insects. However, there is little information on the insect‐suppressive potential of these fungi and possible effects of farming management on this. Meanwhile, changes in natural landscapes due to agricultural intensification have caused considerable biodiversity loss and consequent decay of ecosystem services. However, the adoption of practices such as agroforestry in agroecosystems can foster abiotic and biotic conditions that conserve biodiversity, consequently restoring the provision of ecosystems services. Here, we assessed the effect of management systems (agroforestry or full‐sun) on the pest‐suppressive potential of entomopathogenic fungi in Brazilian coffee plantations. We used the insect bait method coupled with survival analyses to assess the speed of kill by entomopathogenic fungi and their presence in soil samples from both farming systems. We found that insects exposed to agroforestry soils died more quickly than insects exposed to full‐sun soils. Of the fungi isolated from the bait insects, Metarhizium was found most frequently, followed by Beauveria. Meanwhile, Fusarium was frequently isolated as primary or secondary infections. We propose that the differential survival of insects is indicative of a greater suppressive potential by entomopathogenic fungi in agroforestry, and that this could be promoted by the diversified landscape, microclimatic stability, and reduced soil disturbance in agroforestry systems. Furthermore, our results provide a useful demonstration of the potential use of the insect bait method to investigate pest‐suppressive potential through bait insect mortality, and we term this the “bait survival technique.”     

A Novel Binary Mixture of Helicoverpa armigera Single Nucleopolyhedrovirus Genotypic Variants Has Improved Insecticidal Characteristics for Control of Cotton Bollworms

The genotypic diversity of two Spanish isolates of Helicoverpa armigera single nucleopolyhedrovirus (HearSNPV) was evaluated with the aim of identifying mixtures of genotypes with improved insecticidal characteristics for control of the cotton bollworm. Two genotypic variants, HearSP1A and HearSP1B, were cloned in vitro from the most pathogenic wild-type isolate of the Iberian Peninsula, HearSNPV-SP1 (HearSP1-wt). Similarly, six genotypic variants (HearLB1 to -6) were obtained by endpoint dilution from larvae collected from cotton crops in southern Spain that died from virus disease during laboratory rearing. Variants differed significantly in their insecticidal properties, pathogenicity, speed of kill, and occlusion body (OB) production (OBs/larva). HearSP1B was ∼3-fold more pathogenic than HearSP1-wt and the other variants. HearLB1, HearLB2, HeaLB5, and HearLB6 were the fastest-killing variants. Moreover, although highly virulent, HearLB1, HearLB4, and HearLB5 produced more OBs/larva than did the other variants. The co-occluded HearSP1B:LB6 mixture at a 1:1 proportion was 1.7- to 2.8-fold more pathogenic than any single variant and other mixtures tested and also killed larvae as fast as the most virulent genotypes. Serial passage resulted in modified proportions of the component variants of the HearSP1B:LB6 co-occluded mixture, suggesting that transmissibility could be further improved by this process. We conclude that the improved insecticidal phenotype of the HearSP1B:LB6 co-occluded mixture underlines the utility of the genotypic variant dissection and reassociation approach for the development of effective virus-based insecticides.     

Effects of single and mixed infections with wild type and genetically modified Helicoverpa armigera nucleopolyhedrovirus on movement behaviour of cotton bollworm larvae

Naturally occurring insect viruses can modify the behaviour of infected insects and thereby modulate virus transmission. Modifications of the virus genome could alter these behavioural effects. We studied the distance moved and the position of virus‐killed cadavers of fourth instars of Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) infected with a wild‐type genotype of H. armigera nucleopolyhedrovirus (HaSNPV) or with one of two recombinant genotypes of this virus on cotton plants. The behavioural effects of virus infection were examined both in larvae infected with a single virus genotype, and in larvae challenged with mixtures of the wild‐type and one of the recombinant viruses. An egt‐negative virus variant caused more rapid death and lower virus yield in fourth instars, but egt‐deletion did not produce consistent behavioural effects over three experiments, two under controlled glasshouse conditions and one in field cages. A recombinant virus containing the AaIT‐(Androctonus australis Hector) insect‐selective toxin gene, which expresses a neurotoxin derived from a scorpion, caused faster death and cadavers were found lower down the plant than insects infected with unmodified virus. Larvae that died from mixed infections of the AaIT‐expressing recombinant and the wild‐type virus died at positions significantly lower, compared to infection with the pure wild‐type viral strain. The results indicate that transmission of egt‐negative variants of HaSNPV are likely to be affected by lower virus yield, but not by behavioural effects of egt gene deletion. By contrast, the AaIT recombinant will produce lower virus yields as well as modified behaviour, which together can contribute to reduced virus transmission under field conditions. In addition, larvae infected with both the wild‐type virus and the toxin recombinant behaved as larvae infected with the toxin recombinant only, which might be a positive factor for the risk assessment of such toxin recombinants in the environment.     

Aphid and host‐plant genotype × genotype interactions under elevated CO2

1. Elevated CO₂ can alter plant physiology and morphology, and these changes are expected to impact diet quality for insect herbivores. While the plastic responses of insect herbivores have been well studied, less is known about the propensity of insects to adapt to such changes. Genetic variation in insect responses to elevated CO₂ and genetic interactions between insects and their host plants may exist and provide the necessary raw material for adaptation. 2. We used clonal lines of Rhopalosiphum padi (L.) aphids to examine genotype‐specific responses to elevated CO₂. We used the host plant Schedonorus arundinaceus (tall fescue; Schreb), which is capable of asexual reproduction, to investigate host plant genotype‐specific effects and possible host plant‐by‐insect genotype interactions. The abundance and density of three R. padi genotypes on three tall fescue genotypes under three concentrations of CO₂ (ambient, 700, and 1000 ppm) in a controlled greenhouse environment were examined. 3. Aphid abundance decreased in the 700 ppm CO₂ concentration, but increased in the 1000 ppm concentration relative to ambient. The effect of CO₂ on aphid density was dependent on host plant genotype; the density of aphids in high CO₂ decreased for two plant genotypes but was unchanged in one. No interaction between aphid genotype and elevated CO₂ was found, nor did we find significant genotype‐by‐genotype interactions. 4. This study suggests that the density of R. padi aphids feeding on tall fescue may decrease under elevated CO₂ for some plant genotypes. The likely impact of genotype‐specific responses on future changes in the genetic structure of plant and insect populations is discussed.     

Increased nutrient availability decreases insect resistance in cranberry

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The response of resistant kiwifruit (Actinidia chinensis) to armoured scale insect (Diaspididae) feeding

The responses of five experimental genotypes and one commercial variety of kiwifruit (Actinidia chinensis) to attack by two polyphagous, congeneric armoured scale insect pests (Hemiberlesia rapax and H. lataniae) are described. H. lataniae feeding elicits a response in the bark and fruit of all but one of the experimental genotypes, leading to the development of wound periderm over a 4–5 week period, and death of the insect. The response, which differs slightly between tissue types and genotypes, consists of wound periderm formation in a bowl shape beneath and around the insect, preventing its stylet from reaching normal unmodified parenchyma tissue. Wound periderm cell walls become suberised and cells beneath the insect become filled with phenolic compounds. In some cases, cells beneath the insect become hypertrophic or undergo lysis, exhibiting characteristics of a hypersensitive-like response. The remaining genotype showed no physical change in tissue structure in response to H. lataniae feeding, and the insects survived but were substantially reduced in size. These results suggest that both physical and chemical plant resistance responses are involved. In contrast, H. rapax elicited no observable histological response from any of the genotypes and the insects developed normally on bark and fruit. Both insect species developed normally on leaf petioles and these exhibit only slight cell wall thickening in response to their feeding. This unusual plant defensive response to a sucking insect has similarities to simple types of gall formation in response to insect and pathogen attack and has characteristics of resistance gene-mediated models of plant defence.     

Rapid selection and characterization of Cry1F resistance in a Brazilian strain of fall armyworm

Transgenic maize (Zea mays L., Poaceae) event TC1507, producing the Cry1F protein of Bacillus thuringiensis Berliner, has been used for management of the fall armyworm, Spodoptera frugiperda (JE Smith) (Lepidoptera: Noctuidae), in Brazil since 2009. A strain of S. frugiperda, obtained from field collections of larvae in TC1507 maize in Minas Gerais state in 2010, was selected in the laboratory for resistance to Cry1F using leaves of TC1507 maize in two selection regimes. Continuous exposure of larvae to Cry1F was more effective than exposure for 6, 8, and 10 days in the selection of resistant S. frugiperda individuals. With only four generations of laboratory selection, a strain with high levels of resistance to Cry1F was obtained, as indicated by the survival of insects reared on leaves of TC1507 maize plants and by the more than 300‐fold resistance level measured in bioassays with the purified Cry1F protein. Importantly, reciprocal crosses between control and the Cry1F‐selected strains revealed that the resistance is autosomal and incompletely recessive, and the response obtained in the backcross of the F₁ generation with the resistant strain was consistent with simple monogenic inheritance. Additionally, there were no apparent fitness costs associated with resistance either for survival or larval growth on non‐Bt maize leaves. Our findings provide experimental evidence for rapid evolution of Cry1F resistance in S. frugiperda in the laboratory and further reinforce the potential of this species to evolve field resistance to the TC1507 maize as previously reported. The resistant strain isolated in this study provides an opportunity to estimate the resistance allele frequency in the field and to determine the biochemical and molecular basis of the resistance, which should provide further information to assist in the resistance management of S. frugiperda on transgenic maize producing B. thuringiensis proteins.