ISB NEWS REPORT
MAY 2013
Resistance Evolution to Plant-Produced Bt-toxins of the First Generation of
Genetically Engineered Diabrotica-active Bt-Maize Events by Western Corn
Rootworm: Management and Monitoring Considerations
Yann Devos, Lisa N Meihls, József Kiss, Bruce E Hibbard
Introduction
Western corn rootworm (WCR; Diabrotica virgifera
virgifera) is a major coleopteran maize pest in North
America and the European Union (EU), and has
traditionally been managed through crop rotation and
broad-spectrum insecticides. Genetically engineered
(GE) maize transformation events expressing insecticidal
Bacillus thuringiensis (Bt) toxins against corn rootworms
offer an additional management tool for WCR and have
been valuable in reducing insecticide use and increasing
farm productivity in North America. The mode of action
of Bt-toxins is to bind selectively to specific receptors on
the epithelial surface of the midgut of larvae of susceptible
insect species, leading to death of larvae through pore
formation, cell burst and subsequently septicaemia.
Several Diabrotica-active Bt-maize transformation
events are currently grown commercially in Argentina,
Brazil, Canada and the United States (US).
There is a concern that the widespread, repeated,
and exclusive use of the same Bt-maize event expressing
a single Bt-toxin against WCR will create significant
selection pressure and increase the risk of WCR evolving
resistance. Resistance evolution may lead to altered pest
control practices that may cause adverse environmental
effects.
under field conditions after three to seven generations
of selection6-7. As resistance to Cry34Ab1/35Ab1 and
mCry3A also evolved relatively quickly under laboratory
and/or greenhouse settings, field-selected resistance is
possible too. Therefore, vigilance should be exercised,
and farmers who grow Cry3Bb1-, Cry34Ab1/35Ab1- or
mCry3Ab-expressing Bt-maize events should be advised
to put appropriate risk mitigation measures in place to
delay resistance evolution. However, there is also the
possibility of a different mode of action for the binary
Cry34Ab1/35Ab1 proteins9, which may result in an
inherently lower risk of resistance evolution compared
with Cry3Bb1.
Resistance management
To delay resistance evolution and to extend the durability
of Bt-crops, insect resistance management (IRM) plans
relying on the high dose/refuge (HDR) strategy have been
implemented for several Bt-crops in several countries10.
The HDR strategy prescribes planting Bt-crops that
produce a very high concentration of the Bt-toxin, so
that nearly all target insect pests that are heterozygous
for resistance do not survive on it. In addition, a nearby
structured refuge of the non-Bt-crop is required where
the target insect pest does not encounter the Bt-toxin.
(Note that non-Bt-crops or refuges are intended to
mean areas under a crop that does not express Bt-toxins
Resistance evolution
In artificial selection experiments, resistance to the plant- that are active against the target insect pest.) Under
produced Cry3Bb1, Cry34Ab1/35Ab1 and mCry3A these conditions, most of the rare resistant individuals
proteins evolved in a relatively short time (in as few as surviving on the Bt-crop will mate with abundant
three generations with no random mating), and resistance susceptible individuals emerging from nearby refuges to
was found to remain at a similar level after six generations produce heterozygous offspring that are phenotypically
of selection1-5. Laboratory- or greenhouse-selected WCR susceptible. If inheritance of resistance is recessive, then
colonies with Cry3Bb1 and mCry3A resistance have the hybrid progeny from such matings will die on the
increased resistance under field conditions2-3, indicating Bt-crop.
The lack of resistance in some major insect pests
that larval survival on Bt-maize plants in the greenhouse
translated to larval survival on Bt-maize in the field. targeted by Bt-crops attests that the HDR strategy is
Field-selected resistance of WCR to plant-produced Bt- capable of preventing or at least delaying resistance under
toxins is documented in some US maize growing areas field conditions, despite 16 years of intensive use of some
Bt-crops11. In contrast, when the conditions contributing
for Cry3Bb1 only6-8.
Given that Cry3Bb1 resistance has evolved within just to the success of the HDR strategy were not met, field12-14
a few generations in all artificial selection experiments selected resistance to Bt-crops has occurred .
conducted, it is not surprising that resistance evolved
ISB NEWS REPORT
Evidence indicates that several conditions
contributing to the success of the HDR strategy may not
be met for the first generation of Diabrotica-active Btmaize events and WCR: (1) the Bt-toxins are expressed
heterogeneously at a low-to-moderate dose in roots; (2)
resistance alleles may be present at a higher frequency than
initially assumed; (3) WCR may mate in a non-random
manner; (4) resistance traits could have non-recessive
inheritance; and (5) fitness costs may not necessarily
be associated with resistance evolution (reviewed by 4,
15-16). While these factors are expected to increase the
risk of WCR evolving resistance, models developed to
estimate the evolution of resistance in WCR populations
predicted that a 20% refuge can delay resistance evolution
for Bt-maize under certain conditions17-18. Depending
on the underlying model assumptions and parameter
values used in these models, which explore more or less
conservative scenarios, resistance has been predicted to
evolve in three to more than 20 years. Resistance may
evolve fast, as initial resistance allele frequencies in
WCR may be 20-200 times higher than typical empirical
estimates of 0.01-0.001 for other target insect pests15. In
addition, modeling predictions often assume complete
compliance with refuge requirements.
If the high dose condition of the HDR strategy is
not achieved, models predict that resistance evolution
can be delayed by increasing refuge abundance to
compensate for survival of hybrid progeny on Btcrops19-20. The strategy for managing resistance in WCR
would rely solely on a refuge to maintain a susceptible
population. Tabashnik and Gould (2012) recently
advocated increasing refuge abundance by requiring a
50% refuge of non-Bt-maize instead of the current 20%
for the first generation of Diabrotica-active Bt-maize
events15. As the effectiveness of larger refuges may be
diminished by the likely uneven dispersal of WCR under
certain configurations, the authors recognised the need
to fine-tune their recommendation and to account for
different spatial configurations of refuges. Depending on
refuge configurations, increased refuge abundance may
have economic trade-offs that may offset incentives to
implement refuges leading to reduced farmer compliance.
Refuge configurations for Diabrotica-active Btmaize events may be best optimized within the Bt-maize
field as row strips or seed blends. Seed blends will result
in 100% compliance and are more convenient for farmers
to plant than the usual block and row strip refuges21.
The use of seed blends also distributes refuge plants
relatively uniformly within the Bt-crop field. Further,
when compared with block refuges, WCR emerging
from refuge plants emerges more synchronously with
MAY 2013
those emerging from Bt-maize plants in seed blends22.
This increased proximity in both space and time may
facilitate random mating between adults emerging
from Bt-maize and refuge plants compared with block
refuges23. Resistance evolved more slowly under seed
blend scenarios than for WCR colonies reared fully
on Bt-maize2,18,22,24-26, indicating that the WCR biology
seems to lend itself to the seed blend concept.
As WCR larvae feeding on Bt-maize roots may
not be exposed to Bt-toxins uniformly due to their
heterogeneous expression, Bt-maize itself may also act as
(unstructured) refuge. Hibbard et al. (2010) demonstrated
that many or most of WCR individuals initially surviving
on Bt-maize after one generation of selection in the field
had a susceptible phenotype27, suggesting that resistant
individuals from the Bt-maize are not only mating with
susceptible individuals from the refuge, but also with
susceptible individuals that emerged from the Bt-maize
field. Bt-maize that is not truly high dose could thus yield
susceptible adults that are available to mate with any
WCR potentially carrying resistance alleles, and hence
contribute to slow the onset of resistance evolution.
Further, evidence has shown that several grass species
can support the growth of WCR larvae and may therefore
serve as an additional (unstructured) refuge where such
host plants are abundant and appropriately distributed.
Owing to the remaining scientific uncertainties
pertaining to the appropriateness of the HDR strategy for
Bt-crops that are not truly high dose, it is advisable to
complement this strategy with additional IRM measures.
This would ensure that additional and diversified
resistance management strategies, reliant on multiple
tactics to control WCR, are implemented in an integrated
manner28. Therefore, stewardship agreements should
prescribe diversity in cropping and WCR management
practices, and recommend: (1) rotating fields to crops
that are not hosts of WCR larvae; (2) alternating a
specific Diabrotica-active Bt-maize with other Bt-maize
events that express one or more different Bt-toxins
active against WCR; and/or (3) using additional pest
management measures, such as insecticides or biological
control agents, only when and where necessary in Btmaize.
The pyramiding in the same plant of two or multiple
Bt-toxins acting independently on WCR midgut receptors
is expected to effectively delay the evolution of resistance
to either Bt-toxin when most individuals that are resistant
to one Bt-toxin are killed by the other, and when selection
for resistance to one of the Bt-toxins does not cause
cross-resistance to the other29-30. In the absence of crossresistance, models predict that the evolution of resistance
ISB NEWS REPORT
to a Bt-toxin in WCR is generally delayed by pyramided
traits in Bt-maize compared with two single Bt-toxins
deployed sequentially17. The transition to pyramided Btmaize alone is ongoing30, but the current landscape of
Diabrotica-active Bt-maize events comprises a mosaic of
Bt-maize expressing a single or multiple Bt-toxins. This
situation poses a challenge, as mosaics could theoretically
foster the evolution of resistance to pyramided Bt-maize
if WCR evolved resistance to a single toxin Bt-maize
that is also used in pyramided Bt-maize11. The efficacy
of pyramided Bt-maize will also be diminished if crossresistance occurs.
MAY 2013
of Bt-toxins are suitable methods to monitor WCR
susceptibility. Although limitations are associated
with the current diet-based bioassay methods31, results
from these assays can assist in monitoring for WCR
resistance. When the surface treatment of diets is utilized
in diet bioassays to generate dose–response curves
or to discriminate between resistant and susceptible
individuals, instead of incorporating the Bt-toxin
uniformly in the diet, it is important that the top Bt-toxin
concentrations used in the bioassays are sufficiently high
to cause consistently > 50% mortality for either field or
laboratory WCR populations. Alternative methods for
detecting population susceptibility include the use of the
Resistance monitoring
sublethal seedling assay (SSA)1,3,34 and single plant assays
IRM plans for Bt-crops require routine monitoring for in the growth chamber6-7 or greenhouse2. SSA consists
resistance evolution, so that early warning signs indicating of exposing populations of neonate WCR to seedlings
increases in tolerance in the field may be detected31. A from either Bt-maize or the near-isogenic line for a fixed
timely detection of such signs enables actions to limit duration of time and measuring the total larvae recovered
the survival of resistant insects and to slow or prevent and age structure of the larval population. All plant-based
their spread should resistance has evolved among assays have proven adequate to detect subtle changes in
field populations32. A two-pronged approach is usually population susceptibility and are more sensitive than the
followed to monitor resistance evolution. This approach standard diet bioassays that typically rely on mortality or
consists of: (1) measuring the baseline susceptibility of growth inhibition as endpoints.
WCR populations to the Bt-toxins and changes in that
Unexpected field damage caused by WCR: The
susceptibility; and (2) monitoring of unexpected field monitoring of greater-than-expected field damage due to
damage caused by WCR.
WCR is an important component of the early detection
Baseline and monitoring WCR susceptibility: of resistance, as it allows capturing early warning signs
Resistance monitoring aims to measure the baseline indicating increased tolerance in the field and reporting
susceptibility of WCR to the Bt-toxins and shifts in that those in a timely manner. WCR control failures can
susceptibility over time. This baseline susceptibility easily be observed and reported by farmers, provided
should represent the natural variability in response to that farmers know what level of WCR damage is to be
the Bt-toxins among WCR populations across their expected under various conditions and what level of
geographic distribution range, preferably prior to the first WCR control is normally achieved. Such observations
introductions of the Bt-maize33. To obtain comparable may reveal the occurrence of localized tolerance before
data and to detect actual shifts in susceptibility at an early it spreads, and may serve as a trigger for further action.
stage, a consistent methodology in terms of sampling, Farmers could be instructed to use alternative WCR
laboratory bioassays and Bt-toxin standardization is management options. Moreover, sampling of WCR
required13,16.
adults in the fields of concern could be initiated for the
Resistance monitoring, through targeted field purpose of further evaluation and laboratory testing to
sampling in areas where the adoption of Diabrotica-active confirm potential resistance. It is critical that responses
Bt-maize events is the highest and selection pressure is to farmer complaints about product failure and hence
greatest, should reveal changes in susceptibility of these greater-than-expected-field-damage are taken in a timely
WCR populations. Setting the most adequate and precise manner, so that suspected resistance can be confirmed
susceptibility baselines can be achieved through random and remedial measures be implemented, or be refuted
sampling. The sampled WCR populations need to be without undue delays.
large enough to provide sufficient numbers of healthy
individuals for collection. The F2 screen, which aims
Next generation of GE Diabrotica-active maize
to detect rare and highly recessive resistance alleles in events
field-collected individuals, is not considered feasible
for routine resistance monitoring. The dose–response The landscape of GE Diabrotica-active maize events
and discriminating dose assays using the same source is changing quickly with several new products
ISB NEWS REPORT
being at various stages of development or close to
commercialization. This new cohort of products relies
on new Bt-toxins, uses alternative strategies involving
a different mode of action than Bt-toxins, or combines
alternative strategies with existing Bt-toxins. Bt-maize
events expressing a hybrid-like toxin Cry1Ab/Cry3A
protein (eCry3.1Ab) pyramided with mCry3A35 have
been registered for commercial use by the US EPA
and FDA and deregulated by USDA-APHIS, and will
therefore be available for planting in the US in 2014.
The use of RNA interference for the management of
MAY 2013
target insect pests holds considerable promise36, and
its potential was recently demonstrated in the case of
WCR37-39. Whilst empirical data will be needed for each
of these new GE maize products to develop optimized
IRM plans to delay the evolution of resistance, they offer
alternative means to manage WCR, and can complement
existing management options. Unlike the first generation
of Diabrotica-active Bt-maize events40-41, however, the
safety of some of these GE maize products to human
and animal health and the environment has yet to be
investigated fully42-43.
DISCLAIMER
Opinions and views (if any) expressed in this publication do not necessarily reflect those of EFSA. This publication does not disclose
any confidential information or data. Mention of proprietary products is solely for the purpose of providing specific information, and does
not constitute an endorsement or a recommendation by EFSA or USDA-ARS for their use.
References
1. Lefko SA, Nowatzki TM, Thompson SD, Binning RR, Pascual MA, Peters ML, Simbro EJ, Stanley BH, 2008. Characterizing laboratory colonies of western
corn rootworm (Coleoptera: Chrysomelidae) selected for survival on maize containing event DAS-59122-7. Journal of Applied Entomology, 132, 189–204.
2. Meihls LN, Higdon ML, Siegfried BD, Miller NJ, Sappington TW, Ellersieck MR, Spencer TA, Hibbard BE, 2008. Increased survival of western corn rootworm
on transgenic corn within three generations of on-plants greenhouse selection. Proceedings of the National Academy of Sciences of the United States
of America, 105, 19177–19182.
3. Meihls LN, Higdon ML, Ellersieck M, Hibbard BE, 2011. Selection for resistance to mCry3A-expressing transgenic corn in western corn rootworm. Journal
of Economic Entomology, 104, 1045–1054.
4. Meihls LN, Higdon ML, Ellersieck MR, Tabashnik BE, Hibbard BE, 2012. Greenhouse-selected resistance to Cry3Bb1-producing corn in three western corn
rootworm populations. PLoS ONE, 7, e51055.
5. Oswald KJ, French BW, Nielson C, Bagley M, 2011. Selection for Cry3Bb1 resistance in a genetically diverse population of nondiapausing western corn rootworm (Coleoptera: Chrysomelidae). Journal of Economic Entomology, 104, 1038–1044.
6. Gassmann AJ, Petzold-Maxwell JL, Keweshan RS, Dunbar MW, 2011. Field-evolved resistance to Bt maize by western corn rootworm. PLoS ONE, 6, e22629.
7. Gassmann AJ, Petzold-Maxwell JL, Keweshan RS, Dunbar MW, 2012. Western corn rootworm and Bt maize: challenges of pest resistance in the field. GM
Crops & Food: Biotechnology in Agriculture and the Food Chain, 3, 235–244.
8. US EPA, 2011. Updated BPPD IRM review of reports of unexpected Cry3Bb1 damage, Monsanto’s 2009 corn rootworm monitoring report, and revised corn
rootworm resistance monitoring plan for MON 88017, MON 88017 x MON 810, MON 863, MON 863 x MON 810, MON 89034 x TC1507 x MON 88017 x
DAS-59122–7, and MON 89034 x MON 88017 (EPA Reg. Nos. 524–551, 524–552, 524–528, 524–545, and 68467–7); MRIDs 478846–01 and 478875–03.
Available from https://motherjones.com/files/epa-hq-opp-2011–0922–0003.pdf
9. Li H, Olson M, Lin G, Hey T, Tan SY, and Narva KE, 2013. Bacillus thuringiensis Cry34Ab1/Cry35Ab1 interactions with western corn rootworm midgut membrane binding sites. PLoS ONE, 8, e53079.
10. Head GP, Greenplate J, 2012. The design and implementation of insect resistance management programs for Bt crops. GM Crops & Food: Biotechnology
in Agriculture and the Food Chain, 3, 144–153.
11. Siegfried BD, Hellmich RL, 2012. Understanding successful resistance management: The European corn borer and Bt corn in the United States. GM Crops
& Food: Biotechnology in Agriculture and the Food Chain, 3, 184–193.
12. Tabashnik BE, Gassmann AJ, Crowder DW, Carrière Y, 2008. Insect resistance to Bt crops: evidence versus theory? Nature Biotechnology, 26, 199–202.
13. Tabashnik BE, Van Rensburg JBJ, Carrière Y, 2009. Field-evolved insect resistance to Bt crops: definition, theory and data. Journal of Economic Entomology, 102, 2011–2025.
14. Huang F, Andow AA, Buschman LL, 2011. Success of the high-dose/refuge resistance management strategy after 15 years of Bt crop use in North America.
Entomologia Experimentalis et Applicata, 140, 1–16.
15. Tabashnik BE, Gould F, 2012. Delaying corn rootworm resistance to Bt corn. Journal of Economic Entomology, 105, 767–776.
16. Devos Y, Meihls LN, Kiss J, Hibbard BN, 2013. Resistance evolution to the first generation of genetically modified Diabrotica-active Bt-maize events by western
corn rootworm: management and monitoring considerations. Transgenic Research, 22, 269–299.
17. Onstad DW, Meinke LJ, 2010. Modeling evolution of Diabrotica virgifera virgifera (Coleoptera: Chrysomelidae) to transgenic corn with two insecticidal traits.
Journal of Economic Entomology, 103, 849–860.
18. Pan Z, Onstad DW, Nowatzki TM, Stanley BH, Meinke LJ, Flexner JL, 2011. Western corn rootworm (Coleoptera: Chrysomelidae) dispersal and adaptation to
single-toxin transgenic corn deployed with block or blended refuge. Environmental Entomology, 40, 964–978.
19. Gould F, 1998. Sustainability of transgenic insecticidal cultivars: integrating pest genetics and ecology. Annual Review of Entomology, 43, 701–726.
20. Tabashnik BE, Gould F, Carrière Y, 2004. Delaying evolution of insect resistance to transgenic crops by decreasing dominance and heritability. Journal of
Evolutionary Biology, 17, 904–912.
21. Onstad DW, Mitchell PD, Hurley TM, Lundgren JG, Porter RP, Krupke CH, Spencer JL, Difonzo CD, Baute TS, Hellmich RL, Buschman LL, Hutchison WD,
Tooker JF, 2011. Seeds of change: corn seed mixtures for resistance management and integrated pest management. Journal of Economic Entomology,
104, 343–352.
ISB NEWS REPORT
MAY 2013
22. Rudeen ML, Gassmann AJ, 2012. Effects of Cry34/35Ab1 corn on survival and development of western corn rootworm, Diabrotica virgifera virgifera. Pest
Management Science, DOI:10.1002/ps.3425.
23. Murphy AF, Ginzel MD, Krupke CH, 2010. Effect of varying refuge structure upon root damage, emergence and sex ratios of western corn rootworm on transgenic corn. Journal of Economic Entomology, 103, 147–157.
24. Onstad DW, 2006. Modeling larval survival and movement to evaluate seed mixtures of transgenic corn for control of western corn rootworm (Coleoptera:
Chrysomelidae). Journal of Economic Entomology, 99, 1407–1414.
25. Binning RR, Lefko SA, Millsap AY, Thompson SD, Nowatzki TM, 2010. Estimating western corn rootworm (Coleoptera: Chrysomelidae) larval susceptibility to
event DAS-59122–7 maize. Journal of Applied Entomology, 134, 551–561.
26. Zukoff SN, Bailey W, Ellersieck MR, Hibbard BE, 2012. Western corn rootworm larval movement in SmartStax seed blend scenarios. Journal of Economic
Entomology, 104, 1248–1260.
27. Hibbard BE, Clark TL, Ellersieck MR, Meihls LN, El Khishen AA, Kaster V, Steiner H-Y, Kurtz R, 2010. Mortality of western corn rootworm larvae on MIR604
transgenic maize roots: field survivorship has no significant impact on survivorship of F1 progeny on MIR604. Journal of Economic Entomology, 103,
2187–2196.
28. Porter P, Cullen E, Sappington T, Schaafsma A, Pueppke S, Andow D, Bradshaw J, Buschman L, Cardoza YJ, DiFonzo C, French BW, Gassmann A, Gray ME,
Hammond RB, Hibbard B, Krupke CH, Lundgren JG, Ostlie KR, Shields E, Spencer JL, Tooker JF, Youngman RR, 2012. Letter from 22 members and participants of North Central Coordinating Committee NCCC46 and other corn entomologists to EPA, March 5, 2012. Available from http://www.organicconsumers.
org/documents/Letter22Scientists.pdf
29. Storer NP, Thompson GD, Head GP, 2012. Application of pyramided traits against Lepidoptera in insect resistance management for Bt crops. GM Crops &
Food: Biotechnology in Agriculture and the Food Chain, 3, 154–162.
30. Prasifka PL, Rule DM, Storer NP, Nolting SP, Hendrix WH, 2013. Evaluation of corn hybrids expressing Cry34Ab1/Cry35Ab1 and Cry3Bb1 against the western
corn rootworm (Coleoptera: Chrysomelidae). Journal of Economic Entomology, 106, 823–829.
31. Siegfried BD, Spencer T, 2012. Bt resistance monitoring in European corn borer and western corn rootworms. In: Oliver M, Li Y (eds), Gene Containment. New
York: Wiley and Sons, pp. 43–55.
32. Siegfried BD, Spencer T, Crespo AL, Storer NP, Head GP, Owens ED, Guyer D, 2007. Ten years of Bt resistance monitoring in the European corn borer: what
we know, what we don’t know, and what we can do better. American Entomologist, 53, 208–214.
33. Siegfried BD, Vaughn TT, Spencer T, 2005. Baseline susceptibility of western corn rootworm (Coleoptera: Chrysomelidae) to Cry3Bb1 Bacillus thuringiensis
toxin. Journal of Economic Entomology, 98, 1320–1324.
34. Nowatzki TM, Lefko SA, Binning RR, Thompson SD, Spencer TA, Siegfried BD, 2008. Validation of a novel resistance monitoring technique for corn rootworm
(Coleoptera: Chrysomelidae) and event DAS-59122–7 maize. Journal of Applied Entomology, 132, 177–188.
35. Hibbard BE, Frank DL, Kurtz R, Boudreau E, Ellersieck MR, Odhiambo JF, 2011. Mortality impact of Bt transgenic maize roots expressing eCry3.1Ab, mCry3A,
and eCry3.1Ab plus mCry3A on Western corn rootworm larvae in the field. Journal of Economic Entomology, 104, 1584–1591.
36. Burand JP, Hunter WB, 2012. RNAi: future in insect management. Journal of Invertebrate Pathology, 112, S68–S74.
37. Baum JA, Bogaert T, Clinton W, Heck GR, Feldmann P, Ilagan O, Johnson S, Plaetinck G, Munyikwa T, Pleau M, Vaughn T, Roberts J, 2007. Control of coleopteran insect pests through RNA interference. Nature Biotechnology, 25, 1322–1326.
38. Rangasamy M, Siegfried BD, 2011. Validation of RNA interference in western corn rootworm Diabrotica virgifera virgifera LeConte (Coleoptera: Chrysomelidae)
adults. Pest Management Science, 68, 587–591.
39. Bolognesi R, Ramaseshadri P, Anderson J, Bachman P, Clinton W, Flannagan R, Ilagan O, Lawrence C, Levine S, Moar W, Mueller G, Tan J, Uffman J, Wiggins E, Heck G, Segers G, 2012. Characterizing the mechanism of action of double-stranded RNA activity against western corn rootworm (Diabrotica virgifera
virgifera LeConte). PLoS ONE, 7, e47534.
40. Raybould A, Stacey D, Vlachos D, Graser G, Li X, Joseph R, 2007. Non-target organism risk assessment of MIR604 maize expressing mCry3A for control of
corn rootworm. Journal of Applied Entomology, 131, 391–399.
41. Devos Y, De Schrijver A, De Clercq P, Kiss J, Romeis J, 2012. Bt-maize event MON 88017 expressing Cry3Bb1 does not cause harm to non-target organisms.
Transgenic Research, 21, 1191–1214.
42. CERA, 2011. Problem formulation for the environmental risk assessment of RNAi plants: Conference proceedings. Available from http://cera-gmc.org/docs/
cera_publications/pub_08_2011.pdf
43. Petrick JS, Brower-Toland B, Jackson AL, Kier LD, 2013. Safety assessment of food and feed from biotechnology-derived crops employing RNA-mediated
gene regulation to achieve desired traits: a scientific review. Regulatory Toxicology and Pharmacology, DOI:http://dx.doi.org/10.1016/j.yrtph.2013.03.008.
Yann Devos1,*, Lisa N Meihls2, József Kiss3, Bruce E Hibbard4
AFFILIATIONS
1
European Food Safety Authority (EFSA), GMO Unit, Via Carlo Magno 1, IT-43126 Parma, Italy
2
United States Department of Agriculture – National Institute of Food and Agriculture (USDA-NIFA), The Boyce Thompson Institute for
Plant Research, Tower Road, Ithaca, New York, 14853-1801, USA
3
Szent István University, Plant Protection Institute, Pater Károly 1, HU-2100 Gödöllő, Hungary
4
United States Department of Agriculture – Agricultural Research Service (USDA-ARS), Plant Genetics Research Unit, 205 Curtis
Hall, University of Missouri, Columbia, MO 65211, USA
*CORRESPONDING AUTHOR
*European Food Safety Authority, GMO Unit, Via Carlo Magno 1, IT-43126 Parma, Italy
Tel +39-0521/036.344
Fax +39-0521/036.524,
Yann.Devos@efsa.europa.eu