Delaying insect resistance to transgenic crops

Tabashnik, Bruce E.

doi:10.1073/pnas.0810763106

Cited by 125 publications

(105 citation statements)

References 15 publications

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“…This is in contrast to several examples of successful management of insecticide resistant insect pests in which heterozygous resistant individuals are killed by the recommended insecticide field rates (Roush and McKenzie, 1987). Thus, heterozygous insecticide resistance alleles are often functionally recessive in the field under insecticide selection and this phenomenon has provided the basis for successful application of a high-dose refuge strategy to significantly delay and minimize insecticide resistance evolution in transgenic Bt crops (Tabashnik, 2008). In our study at high diclofop-methyl rates incomplete dominance was evident (Figure 1) but, herbicides cannot be used at very high doses because of regulatory restrictions, crop selectivity or cost.…”

Section: Discussionmentioning

confidence: 89%

Genetic control of a cytochrome P450 metabolism-based herbicide resistance mechanism in Lolium rigidum

2010

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The dynamics of herbicide resistance evolution in plants are influenced by many factors, especially the biochemical and genetic basis of resistance. Herbicide resistance can be endowed by enhanced rates of herbicide metabolism because of the activity of cytochrome P450 enzymes, although in weedy plants the genetic control of cytochrome P450-endowed herbicide resistance is poorly understood. In this study we have examined the genetic control of P450 metabolism-based herbicide resistance in a well-characterized Lolium rigidum biotype. The phenotypic resistance segregation in herbicide resistant and susceptible parents, F1, F2 and backcross (BC) families was analyzed as plant survival following treatment with the chemically unrelated herbicides diclofop-methyl or chlorsulfuron. Dominance and nuclear gene inheritance was observed in F1 families when treated at the recommended field doses of both herbicides.The segregation values of P450 herbicide resistance phenotypic traits observed in F2 and BC families was consistent with resistance endowed by two additive genes in most cases. In obligate out-crossing species such as L. rigidum, herbicide selection can easily result in accumulation of resistance genes within individuals.

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Section: Discussionmentioning

confidence: 89%

Genetic control of a cytochrome P450 metabolism-based herbicide resistance mechanism in Lolium rigidum

2010

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“…This evidence is unsatisfying because it does not allow analysis of longer-term developments. For example, resistance build-up in pest populations or growing importance of secondary pests may potentially lower Bt benefits over time (22)(23)(24). Second, most impact studies do not properly control for nonrandom selection bias (17), which may occur when more successful farmers adopt the new technology earlier or more widely (25).…”

mentioning

confidence: 99%

Economic impacts and impact dynamics of Bt ( Bacillus thuringiensis ) cotton in India

Kathage

Qaim

2012

Proc. Natl. Acad. Sci. U.S.A.

243

190

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Despite widespread adoption of genetically modified crops in many countries, heated controversies about their advantages and disadvantages continue. Especially for developing countries, there are concerns that genetically modified crops fail to benefit smallholder farmers and contribute to social and economic hardship. Many economic studies contradict this view, but most of them look at short-term impacts only, so that uncertainty about longer-term effects prevails. We address this shortcoming by analyzing economic impacts and impact dynamics of Bt cotton in India. Building on unique panel data collected between 2002 and 2008, and controlling for nonrandom selection bias in technology adoption, we show that Bt has caused a 24% increase in cotton yield per acre through reduced pest damage and a 50% gain in cotton profit among smallholders. These benefits are stable; there are even indications that they have increased over time. We further show that Bt cotton adoption has raised consumption expenditures, a common measure of household living standard, by 18% during the 2006–2008 period. We conclude that Bt cotton has created large and sustainable benefits, which contribute to positive economic and social development in India.

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“…Evolution of resistance by pests is the primary threat to the continued efficacy of Bt crops (2)(3)(4)(5)(6). Analysis of monitoring data suggests that the refuge strategy, which requires non-Bt host plants near Bt crops to promote survival of susceptible pests, has delayed pest resistance to Bt crops (4,7). Although Bt crops have remained effective against most targeted pest populations, 3 cases have been reported of field-evolved pest resistance to Bt crops that produce only 1 toxin (4,(7)(8)(9)(10)(11).…”

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confidence: 99%

Asymmetrical cross-resistance betweenBacillus thuringiensistoxins Cry1Ac and Cry2Ab in pink bollworm

Tabashnik

Unnithan

Masson

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

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115

106

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Transgenic crops producing Bacillus thuringiensis (Bt) toxins kill some key insect pests and can reduce reliance on insecticide sprays. Sustainable use of such crops requires methods for delaying evolution of resistance by pests. To thwart pest resistance, some transgenic crops produce 2 different Bt toxins targeting the same pest. This ''pyramid'' strategy is expected to work best when selection for resistance to 1 toxin does not cause cross-resistance to the other toxin. The most widely used pyramid is transgenic cotton producing Bt toxins Cry1Ac and Cry2Ab. Cross-resistance between these toxins was presumed unlikely because they bind to different larval midgut target sites. Previous results showed that laboratory selection with Cry1Ac caused little or no cross-resistance to Cry2A toxins in pink bollworm (Pectinophora gossypiella), a major cotton pest. We show here, however, that laboratory selection of pink bollworm with Cry2Ab caused up to 420-fold crossresistance to Cry1Ac as well as 240-fold resistance to Cry2Ab. Inheritance of resistance to high concentrations of Cry2Ab was recessive. Larvae from a laboratory strain resistant to Cry1Ac and Cry2Ab in diet bioassays survived on cotton bolls producing only Cry1Ac, but not on cotton bolls producing both toxins. Thus, the asymmetrical cross-resistance seen here does not threaten the efficacy of pyramided Bt cotton against pink bollworm. Nonetheless, the results here and previous evidence indicate that crossresistance occurs between Cry1Ac and Cry2Ab in some key cotton pests. Incorporating the potential effects of such cross-resistance in resistance management plans may help to sustain the efficacy of pyramided Bt crops.evolution ͉ genetically engineered crops ͉ transgenic crops ͉ Bt cotton

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Delaying insect resistance to transgenic crops

Cited by 125 publications

References 15 publications

Genetic control of a cytochrome P450 metabolism-based herbicide resistance mechanism in Lolium rigidum

Genetic control of a cytochrome P450 metabolism-based herbicide resistance mechanism in Lolium rigidum

Economic impacts and impact dynamics of Bt ( Bacillus thuringiensis ) cotton in India

Asymmetrical cross-resistance betweenBacillus thuringiensistoxins Cry1Ac and Cry2Ab in pink bollworm

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