Effects of four nematode species on fitness costs of pink bollworm resistance to Bacillus thuringiensis toxin CrylAc

Eugene R. Hannon, Mark S. Sisterson, S Patricia Stock, Yves Carriere, Bruce E Tabashnik, Aaron J. Gassmann

Research output: Contribution to journalArticle

9 Citations (Scopus)

Abstract

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 nematode Steinernema riobrave Cabanillas, Poinar, and Raulston but no fitness costs were imposed by Steinernema carpocapsae Weiser, Steinernema sp. (ML18 strain), or Heterorhabditis sonorensis Stock, Rivera-Orduo, 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.

Original languageEnglish (US)
Pages (from-to)1821-1831
Number of pages11
JournalJournal of Economic Entomology
Volume103
Issue number5
DOIs
StatePublished - Oct 2010

Fingerprint

Pectinophora gossypiella
Bacillus thuringiensis
toxin
nematode
fitness
toxins
Steinernema riobravis
Nematoda
entomopathogenic nematodes
cost
cotton
Heterorhabditidae
Heterorhabditis
Steinernematidae
Steinernema
Steinernema carpocapsae
Gelechiidae
resistance management
crops
Gossypium hirsutum

Keywords

  • Ecological negative cross-resistance
  • Pectinophora gossypiella
  • resistance management
  • simulation modeling
  • Steinernema riobrave

ASJC Scopus subject areas

  • Insect Science
  • Ecology

Cite this

Effects of four nematode species on fitness costs of pink bollworm resistance to Bacillus thuringiensis toxin CrylAc. / Hannon, Eugene R.; Sisterson, Mark S.; Stock, S Patricia; Carriere, Yves; Tabashnik, Bruce E; Gassmann, Aaron J.

In: Journal of Economic Entomology, Vol. 103, No. 5, 10.2010, p. 1821-1831.

Research output: Contribution to journalArticle

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abstract = "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 nematode Steinernema riobrave Cabanillas, Poinar, and Raulston but no fitness costs were imposed by Steinernema carpocapsae Weiser, Steinernema sp. (ML18 strain), or Heterorhabditis sonorensis Stock, Rivera-Orduo, 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.",
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