Effects of Pink Bollworm Resistance to &lt;I&gt;Bacillus thuringiensis&lt;/I&gt; on Phenoloxidase Activity and Susceptibility to Entomopathogenic Nematodes

Gassmann, Aaron J.; Fabrick, Jeffrey A.; Sisterson, Mark S.; Hannon, Eugene R.; Stock, S. Patricia; Carrière, Yves; Tabashnik, Bruce E.

doi:10.1603/029.102.0348

Cited by 34 publications

(41 citation statements)

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“…We used a computer model to assess how the Þtness cost imposed by S. riobrave in this study could affect the evolution of resistance by pink bollworm to Bt cotton producing Cry1Ac. We used a previously described spatially explicit, stochastic model with parameters based on the biology of pink bollworm in Bt and non-Bt cotton Þelds (Sisterson et al 2004(Sisterson et al , 2005Gassmann et al 2008Gassmann et al , 2009b. We used the same basic model structure as in Gassmann et al (2008Gassmann et al ( , 2009b, but we examined different assumptions about the presence of nematodes and their effects on pink bollworm population dynamics, as detailed below.…”

Section: Methodsmentioning

confidence: 99%

“…When resistance alleles are rare in a population, the majority of these alleles will be carried by heterozygous individuals (Hartl and Clark 1997). Thus, nonrecessive Þtness costs, which by deÞnition affect heterozygous individuals, will be the most effective at delaying resistance (Carriè re and Tabashnik 2001, Gassmann et al 2009b. Both the magnitude and dominance of Þtness costs of Bt resistance can be affected by several ecological factors, including host plant species, host plant cultivar, intraspeciÞc competition, entomopathogenic viruses, and entomopathogenic nematodes (Gassmann et al 2009a).…”

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confidence: 99%

“…Pink bollworm pupates in the soil, and Þeld data suggest that entomopathogenic nematodes may be a useful management tool to control this pest in non-Bt refuge Þelds (Gouge et al 1998, Gouge et al 1999. Previous work with two species of entomopathogenic nematode showed that Þtness costs of resistance to Cry1Ac were consistently magniÞed by Steinernema riobrave Cabanillas, Poinar, and Raulston, but that Heterorhabditis bacteriophora Poinar seldom increased Þtness costs (Gassmann et al 2006(Gassmann et al , 2009b.…”

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confidence: 99%

“…In previous modeling work, we evaluated the potential effects of applying the nematode S. riobrave to all refuge Þelds of non-Bt cotton (Gassmann et al , 2009b. However, because nematodes are often costly to apply and provide inconsistent suppression of pest populations, it is probably not practical to treat large numbers of Þelds with nematodes (Gaugler et al 1997, Lacey et al 2001.…”

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Effects of Four Nematode Species on Fitness Costs of Pink Bollworm Resistance to Bacillus thuringiensis Toxin Cry1Ac

et al. 2010

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Evolution of resistance by pests can reduce the efficacy of transgenic crops that produce insecticidal toxins from the bacterium Bacillus thuringiensis Berliner (Bt). In conjunction with refuges of non-Bt host plants, fitness costs can delay the evolution of resistance. Furthermore, fitness costs often vary with ecological conditions, suggesting that agricultural landscapes can be manipulated to magnify fitness costs and thereby prolong the efficacy of Bt crops. In the current study, we tested the effects of four species of entomopathogenic nematodes (Steinernematidae and Heterorhabditidae) on the magnitude and dominance of fitness costs of resistance to Bt toxin CrylAc in pink bollworm, Pectinophora gossypiella (Saunders) (Lepidoptera: Gelechiidae). For more than a decade, field populations of pink bollworm in the United States have remained susceptible to Bt cotton Gossypium hirsutum L. producing CrylAc; however, we used laboratory strains that had a mixture of susceptible and resistant individuals. In laboratory experiments, dominant fitness costs were imposed by the nematodeSteinernema riobrave Cabanillas, Poinar, and Raulston but no fitness costs were imposed bySteinernema carpocapsae Weiser, Steinernema sp. (ML18 strain), or Heterorhabditis sonorensis Stock, Rivera-Orduño, and Flores-Lara. In computer simulations, evolution of resistance to CrylAc by pink bollworm was substantially delayed by treating some non-Bt cotton refuge fields with nematodes that imposed a dominant fitness cost, similar to the cost observed in laboratory experiments with S. riobrave. Based on the results here and in related studies, we conclude that entomopathogenic nematodes could bolster insect resistance management, but the success of this approach will depend on selecting the appropriate species of nematode and environment, as fitness costs were magnified by only two of five species evaluated and also depended on environmental factors. RightsWorks produced by employees of the U.S. Government as part of their official duties are not copyrighted within the U.S. The content of this document is not copyrighted. ABSTRACT Evolution of resistance by pests can reduce the efÞcacy of transgenic crops that produce insecticidal toxins from the bacterium Bacillus thuringiensis Berliner (Bt). In conjunction with refuges of non-Bt host plants, Þtness costs can delay the evolution of resistance. Furthermore, Þtness costs often vary with ecological conditions, suggesting that agricultural landscapes can be manipulated to magnify Þtness costs and thereby prolong the efÞcacy of Bt crops. In the current study, we tested the effects of four species of entomopathogenic nematodes (Steinernematidae and Heterorhabditidae) on the magnitude and dominance of Þtness costs of resistance to Bt toxin Cry1Ac in pink bollworm, Pectinophora gossypiella (Saunders) (Lepidoptera: Gelechiidae). For more than a decade, Þeld populations of pink bollworm in the United States have remained susceptible to Bt cotton Gossypium hirsutum L. producing Cry1Ac; however,...

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Effects of Four Nematode Species on Fitness Costs of Pink Bollworm Resistance to Bacillus thuringiensis Toxin Cry1Ac

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“…2009). However, fitness costs explicitly associated with resistance to Bt crops remain poorly understood (Jakka, Knight & Jurat‐Fuentes 2014).…”

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confidence: 99%

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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Diversity and Defence: Plant–Herbivore Interactions at Multiple Scales and Trophic Levels

Horgan

2012

Biodiversity and Insect Pests

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Effects of Pink Bollworm Resistance to <I>Bacillus thuringiensis</I> on Phenoloxidase Activity and Susceptibility to Entomopathogenic Nematodes

Cited by 34 publications

References 56 publications

Effects of Four Nematode Species on Fitness Costs of Pink Bollworm Resistance to Bacillus thuringiensis Toxin Cry1Ac

Effects of Four Nematode Species on Fitness Costs of Pink Bollworm Resistance to Bacillus thuringiensis Toxin Cry1Ac

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

Diversity and Defence: Plant–Herbivore Interactions at Multiple Scales and Trophic Levels

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