Fitness Costs Associated With Field-Evolved Resistance to Bt Maize in &lt;I&gt;Spodoptera frugiperda&lt;/I&gt; (Lepidoptera: Noctuidae)

Jakka, Siva R. K.; Knight, V.R.; Jurat-Fuentes, Juan Luís

doi:10.1603/ec13326

Cited by 80 publications

(86 citation statements)

References 23 publications

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“…Competition costs only impair the spread of the resistance allele when the population exceeds a threshold density beyond which resistant insects fail to compete and decline. Such a cost is more reflective of the weaker fitness costs reported in field-evolved resistance to Bt crops (Jakka, Knight & Jurat-Fuentes 2014;Dangal & Huang 2015;Ingber & Gassmann 2015). Competition costs were insufficient to delay the evolution of resistance under constant selection (Fig.…”

Section: Discussionmentioning

confidence: 99%

“…When fitness costs are context sensitive, the resistance allele frequency may not necessarily decline in the absence of selection. Unless the context is appropriate, the resistance allele may behave as if it were cost-free and resistance will evolve more rapidly (Jakka, Knight & Jurat-Fuentes 2014;Garc ıa et al 2015;Ingber & Gassmann 2015).…”

Section: Introductionmentioning

confidence: 99%

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Type of fitness cost influences the rate of evolution of resistance to transgenic Bt crops

Hackett¹

2016

2016 International Congress of Entomology

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Summary1. The evolution of resistance to pesticides by insect pests is a significant challenge for sustainable agriculture. For transgenic crops expressing Bacillus thuringiensis (Bt), crystalline (Cry) toxins resistance evolution may be delayed by the high-dose/refuge strategy in which a non-toxic refuge is planted to promote the survival of susceptible insects. The high-dose/refuge strategy may interact with fitness costs associated with resistance alleles to further delay resistance. However, while a diverse range of fitness costs are reported in the field, they are typically represented as a fixed reduction in survival or viability which is insensitive to ecological conditions such as competition. Furthermore, the potential dynamic consequences of restricting susceptible insects to a refuge which represents only a fraction of the available space have rarely been considered. 2. We present a generalized discrete time model which utilizes dynamic programming methods to derive the optimal management decisions for the control of a theoretical insect pest population exposed to Bt crops. We consider three genotypes (susceptible homozygotes, resistant homozygotes and heterozygotes) and implement fitness costs of resistance to Bt toxins as either a decrease in the relative competitive ability of resistant insects or as a penalty on fecundity. Model analysis is repeated and contrasted for two types of density dependence: uniform density dependence which operates equally across the landscape and heterogeneous density dependence where the intensity of competition scales inversely with patch size and is determined separately for the refuge and Bt crop. 3. When the planting of Bt is decided optimally, fitness costs to fecundity allow for the planting of larger areas of Bt crops than equivalent fitness costs that reduce the competitive ability of resistant insects. 4. Heterogeneous competition only influenced model predictions when the proportional area of Bt planted in each season was decided optimally and resistance was not recessive. 5. Synthesis and applications. The high-dose/refuge strategy alone is insufficient to preserve susceptibility to transgenic Bacillus thuringiensis (Bt) crops in the long term when constraints upon the evolution of resistance are not insurmountable. Fitness costs may enhance the delaying effect of the refuge, but the extent to which they do so depends upon how the cost is realized biologically. Fitness costs which apply independently of other variables may be more beneficial to resistance management than costs which are only visible to selection under a limited range of ecological conditions.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Type of fitness cost influences the rate of evolution of resistance to transgenic Bt crops

Hackett¹

2016

2016 International Congress of Entomology

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“…Competition costs only impair the spread of the resistance allele when the population exceeds a threshold density beyond which resistant insects fail to compete and decline. Such a cost is more reflective of the weaker fitness costs reported in field‐evolved resistance to Bt crops (Jakka, Knight & Jurat‐Fuentes 2014; Dangal & Huang 2015; Ingber & Gassmann 2015). Competition costs were insufficient to delay the evolution of resistance under constant selection (Fig.…”

Section: Discussionmentioning

confidence: 99%

“…This shortfall in available data can be partly attributed to the success of the high‐dose/refuge strategy; if instances of field‐evolved resistance are rare, so studies of field‐evolved resistance to Bt crops are similarly sparse. Recent efforts to categorize and quantify fitness costs associated with field‐evolved resistance to Bt crops have reported variable results (Jakka, Knight & Jurat‐Fuentes 2014; Dangal & Huang 2015; García et al . 2015; Ingber & Gassmann 2015).…”

Section: Introductionmentioning

confidence: 99%

“…When fitness costs are context sensitive, the resistance allele frequency may not necessarily decline in the absence of selection. Unless the context is appropriate, the resistance allele may behave as if it were cost‐free and resistance will evolve more rapidly (Jakka, Knight & Jurat‐Fuentes 2014; García et al . 2015; Ingber & Gassmann 2015).…”

Section: Introductionmentioning

confidence: 99%

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Type of fitness cost influences the rate of evolution of resistance to transgenic Bt crops

Hackett

Bonsall

2016

Journal of Applied Ecology

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Summary The evolution of resistance to pesticides by insect pests is a significant challenge for sustainable agriculture. For transgenic crops expressing Bacillus thuringiensis (Bt), crystalline (Cry) toxins resistance evolution may be delayed by the high‐dose/refuge strategy in which a non‐toxic refuge is planted to promote the survival of susceptible insects. The high‐dose/refuge strategy may interact with fitness costs associated with resistance alleles to further delay resistance. However, while a diverse range of fitness costs are reported in the field, they are typically represented as a fixed reduction in survival or viability which is insensitive to ecological conditions such as competition. Furthermore, the potential dynamic consequences of restricting susceptible insects to a refuge which represents only a fraction of the available space have rarely been considered.We present a generalized discrete time model which utilizes dynamic programming methods to derive the optimal management decisions for the control of a theoretical insect pest population exposed to Bt crops. We consider three genotypes (susceptible homozygotes, resistant homozygotes and heterozygotes) and implement fitness costs of resistance to Bt toxins as either a decrease in the relative competitive ability of resistant insects or as a penalty on fecundity. Model analysis is repeated and contrasted for two types of density dependence: uniform density dependence which operates equally across the landscape and heterogeneous density dependence where the intensity of competition scales inversely with patch size and is determined separately for the refuge and Bt crop.When the planting of Bt is decided optimally, fitness costs to fecundity allow for the planting of larger areas of Bt crops than equivalent fitness costs that reduce the competitive ability of resistant insects.Heterogeneous competition only influenced model predictions when the proportional area of Bt planted in each season was decided optimally and resistance was not recessive. Synthesis and applications. The high‐dose/refuge strategy alone is insufficient to preserve susceptibility to transgenic Bacillus thuringiensis (Bt) crops in the long term when constraints upon the evolution of resistance are not insurmountable. Fitness costs may enhance the delaying effect of the refuge, but the extent to which they do so depends upon how the cost is realized biologically. Fitness costs which apply independently of other variables may be more beneficial to resistance management than costs which are only visible to selection under a limited range of ecological conditions.

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Inheritance, fitness costs, incomplete resistance and feeding preferences in a laboratory-selected MON810-resistant strain of the true armywormMythimna unipuncta

et al. 2015

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Fitness Costs Associated With Field-Evolved Resistance to Bt Maize in <I>Spodoptera frugiperda</I> (Lepidoptera: Noctuidae)

Cited by 80 publications

References 23 publications

Type of fitness cost influences the rate of evolution of resistance to transgenic Bt crops

Type of fitness cost influences the rate of evolution of resistance to transgenic Bt crops

Type of fitness cost influences the rate of evolution of resistance to transgenic Bt crops

Inheritance, fitness costs, incomplete resistance and feeding preferences in a laboratory-selected MON810-resistant strain of the true armywormMythimna unipuncta

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