An In-Field Screen for Early Detection and Monitoring of Insect Resistance to &lt;I&gt;Bacillus thuringiensis&lt;/I&gt; in Transgenic Crops

Venette, Robert C.; Hutchison, W. D.; Andow, D. D. A

doi:10.1603/0022-0493-93.4.1055

Cited by 48 publications

(54 citation statements)

References 39 publications

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“…Such a definition of field-evolved resistance incorporates the outcomes of genetically mediated changes in sensitivity of the target pest to Bt toxins, such as the potential for incomplete resistance and fitness costs where pest feeding on Bt crops increases but development to adult is delayed or incomplete [31]. In addition to the laboratory bioassays to determine resistance, comparison of target pest susceptibility and control efficacy in paired fields of Bt and non-Bt crops is a practical method to monitor evolution of resistance in the field [31,47]. Resistance definition by Tabashnik et al .…”

Section: Introductionmentioning

confidence: 99%

Field-Evolved Resistance in Corn Earworm to Cry Proteins Expressed by Transgenic Sweet Corn

2016

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BackgroundTransgenic corn engineered with genes expressing insecticidal toxins from the bacterium Bacillus thuringiensis (Berliner) (Bt) are now a major tool in insect pest management. With its widespread use, insect resistance is a major threat to the sustainability of the Bt transgenic technology. For all Bt corn expressing Cry toxins, the high dose requirement for resistance management is not achieved for corn earworm, Helicoverpa zea (Boddie), which is more tolerant to the Bt toxins.Methodology/Major FindingsWe present field monitoring data using Cry1Ab (1996–2016) and Cry1A.105+Cry2Ab2 (2010–2016) expressing sweet corn hybrids as in-field screens to measure changes in field efficacy and Cry toxin susceptibility to H. zea. Larvae successfully damaged an increasing proportion of ears, consumed more kernel area, and reached later developmental stages (4th - 6th instars) in both types of Bt hybrids (Cry1Ab—event Bt11, and Cry1A.105+Cry2Ab2—event MON89034) since their commercial introduction. Yearly patterns of H. zea population abundance were unrelated to reductions in control efficacy. There was no evidence of field efficacy or tissue toxicity differences among different Cry1Ab hybrids that could contribute to the decline in control efficacy. Supportive data from laboratory bioassays demonstrate significant differences in weight gain and fitness characteristics between the Maryland H. zea strain and a susceptible strain. In bioassays with Cry1Ab expressing green leaf tissue, Maryland H. zea strain gained more weight than the susceptible strain at all concentrations tested. Fitness of the Maryland H. zea strain was significantly lower than that of the susceptible strain as indicated by lower hatch rate, longer time to adult eclosion, lower pupal weight, and reduced survival to adulthood.Conclusions/SignificanceAfter ruling out possible contributing factors, the rapid change in field efficacy in recent years and decreased susceptibility of H. zea to Bt sweet corn provide strong evidence of field-evolved resistance in H. zea populations to multiple Cry toxins. The high adoption rate of Bt field corn and cotton, along with the moderate dose expression of Cry1Ab and related Cry toxins in these crops, and decreasing refuge compliance probably contributed to the evolution of resistance. Our results have important implications for resistance monitoring, refuge requirements and other regulatory policies, cross-resistance issues, and the sustainability of the pyramided Bt technology.

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Section: Introductionmentioning

confidence: 99%

Field-Evolved Resistance in Corn Earworm to Cry Proteins Expressed by Transgenic Sweet Corn

2016

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“…This screening procedure increases the likelihood of detecting recessive and rare resistance alleles over the other two screening procedures cited. In particular, the F 2 screen can be used to estimate the frequency of any resistance allele sampled from the natural population and is suitable for estimating the statistical robustness of any experiment (see and Venette et al (2000Venette et al ( , 2002 for a more detailed comparison of the various screening methods). The feasibility of this method has been demonstrated and it has been used to estimate the frequencies of Bt resistance alleles in field populations of the European corn borer, Ostrinia nubilalis Bourguet et al 2003), and the rice stem borer, Scirpophaga incertulas (Bentur et al 2000).…”

Section: Discussionmentioning

confidence: 99%

Initial frequency of alleles conferring resistance toBacillus thuringiensispoplar in a field population ofChrysomela tremulae

Génissel

Augustin²,

Courtin³

et al. 2003

Proc. R. Soc. Lond. B

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Globally, the estimated total area planted with transgenic plants producing Bacillus thuringiensis (Bt) toxins was 12 million hectares in 2001. The risk of target pests becoming resistant to these toxins has led to the implementation of resistance-management strategies. The efficiency and sustainability of these strategies, including the high-dose plus refuge strategy currently recommended for North American maize, depend on the initial frequency of resistance alleles. In this study, we estimated the initial frequencies of alleles conferring resistance to transgenic Bt poplars producing Cry3A in a natural population of the poplar pest Chrysomela tremulae (Coleoptera: Chrysomelidae). We used the F 2 screen method developed for detecting resistance alleles in natural pest populations. At least three parents of the 270 lines tested were heterozygous for a major Bt resistance allele. We estimated mean resistance-allele frequency for the period 1999-2001 at 0.0037 (95% confidence interval = 0.000 45-0.0080) with a detection probability of 90%. These results demonstrate that (i) the F 2 screen method can be used to detect major alleles conferring resistance to Bt-producing plants in insects and (ii) the initial frequency of alleles conferring resistance to Bt toxin can be close to the highest theoretical values that are expected prior to the use of Bt plants if considering fitness costs and typical mutation rates.

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“…Two methods with potentially higher sensitivity for detecting resistance alleles have not been chosen for the monitoring: the F 2 screen proposed by Andow and Alstad (1998) and the in-field screen suggested by Venette et al (2000). 10 This Panel serves as the primary scientific peer review mechanism of the Office of Pesticide Programs in EPA and is structured to provide expert assessment of pesticide and pesticide-related matters facing the Agency (SAP (Scientific Advisory Panel), 2001).…”

Section: Alternative Methodsmentioning

confidence: 99%

“…The in-field screen concept involves using the Bt corn itself as an in-field discriminatory dose for wild ECB populations (Venette et al, 2000). The density of ECB collected in the Bt corn is compared with the density in a non-Bt corn plot located close by.…”

Section: Alternative Methodsmentioning

confidence: 99%

Regulating insect resistance management: the case of non-Bt corn refuges in the US

Bourguet

Desquilbet

Lemarié

2005

Journal of Environmental Management

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In this paper, we analyze the insect resistance management (IRM) plan put in place by the US Environmental Protection Agency (EPA) to delay the evolution of resistance to Bt corn in natural populations of the European corn borer, Ostrinia nubilalis Hübner. This IRM plan is the most impressive mandatory IRM system ever developed. It forms a coherent whole and includes mandatory refuges, actions to increase growers' compliance and a program for monitoring the evolution of resistance. However, our analysis suggests that two components of this IRM plan are not entirely satisfactory: growers' compliance and monitoring of the evolution of resistance. Moreover, the implementation of these two components of IRM has been required of the registrants, whose incentives for IRM are probably lower than the social optimum. Our analysis suggests that alternatives to the IRM plan currently in place could improve these two components.

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An In-Field Screen for Early Detection and Monitoring of Insect Resistance to <I>Bacillus thuringiensis</I> in Transgenic Crops

Cited by 48 publications

References 39 publications

Field-Evolved Resistance in Corn Earworm to Cry Proteins Expressed by Transgenic Sweet Corn

Field-Evolved Resistance in Corn Earworm to Cry Proteins Expressed by Transgenic Sweet Corn

Initial frequency of alleles conferring resistance toBacillus thuringiensispoplar in a field population ofChrysomela tremulae

Regulating insect resistance management: the case of non-Bt corn refuges in the US

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