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Jorg Romeis - One of the best experts on this subject based on the ideXlab platform.
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Bt-maize event MON 88017 expressing Cry3Bb1 does not cause harm to non-target organisms
Transgenic Research, 2012Co-Authors: Yann Devos, Adinda Schrijver, Patrick Clercq, József Kiss, Jorg RomeisAbstract:This review paper explores whether the cultivation of the genetically modified Bt -maize transformation event MON 88017, expressing the insecticidal Cry3Bb1 protein against corn rootworms (Coleoptera: Chrysomelidae), causes adverse effects to non-target organisms (NTOs) and the ecological and anthropocentric functions they provide. Available data do not reveal adverse effects of Cry3Bb1 on various NTOs that are representative of potentially exposed taxonomic and functional groups, confirming that the insecticidal activity of the Cry3Bb1 protein is limited to species belonging to the coleopteran family of Chrysomelidae. The potential risk to non-target chrysomelid larvae ingesting maize MON 88017 pollen deposited on host plants is minimal, as their abundance in maize fields and the likelihood of encountering harmful amounts of pollen in and around maize MON 88017 fields are low. Non-target adult chrysomelids, which may occasionally feed on maize MON 88017 plants, are not expected to be affected due to the low activity of the Cry3Bb1 protein on adults. Impacts on NTOs caused by potential unintended changes in maize MON 88017 are not expected to occur, as no differences in composition, phenotypic characteristics and plant-NTO interactions were observed between maize MON 88017 and its near-isogenic line.
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Sensitivity of the cereal leaf beetle Oulema melanopus (Coleoptera: Chrysomelidae) to Bt maize-expressed Cry3Bb1 and Cry1Ab
Arthropod-Plant Interactions, 2012Co-Authors: Michael Meissle, Simon Knecht, Mario Waldburger, Jorg RomeisAbstract:The sensitivity of the cereal leaf beetle, Oulema melanopus (Coleoptera: Chrysomelidae), to maize-expressed Bacillus thuringiensis (Bt) proteins was investigated in the present study. Neonate larvae of O. melanopus were caged on leaves of Cry3Bb1-expressing (MON88017) or Cry1Ab-expressing (MON810) Bt maize, the corresponding near-isolines, or two non-related, conventional maize varieties. Larval survival was reduced on Cry3Bb1-expressing, but not on Cry1Ab-expressing maize compared with conventional varieties. Differences among conventional varieties were also present. The amount of eaten leaf material, developmental time to prepupal stage, and prepupal weight did not differ between Bt maize varieties and their corresponding near-isolines. In an additional feeding study with newly emerged adults, survival and beetle weight did not differ when leaves of Cry3Bb1-expressing maize or the near-isoline were offered as food over 3 weeks. ELISA measurements revealed that larvae feeding on Bt maize contained rather high Cry3Bb1 or Cry1Ab levels, which were in the same order of magnitude as the leaves. In contrast, concentrations in feces were one order, and concentrations in prepupae and adults two orders of magnitude lower.
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Bt -maize event MON 88017 expressing Cry3Bb1 does not cause harm to non-target organisms
Transgenic research, 2012Co-Authors: Yann Devos, Adinda Schrijver, Patrick Clercq, József Kiss, Jorg RomeisAbstract:This review paper explores whether the cultivation of the genetically modified Bt-maize transformation event MON 88017, expressing the insecticidal Cry3Bb1 protein against corn rootworms (Coleoptera: Chrysomelidae), causes adverse effects to non-target organisms (NTOs) and the ecological and anthropocentric functions they provide. Available data do not reveal adverse effects of Cry3Bb1 on various NTOs that are representative of potentially exposed taxonomic and functional groups, confirming that the insecticidal activity of the Cry3Bb1 protein is limited to species belonging to the coleopteran family of Chrysomelidae. The potential risk to non-target chrysomelid larvae ingesting maize MON 88017 pollen deposited on host plants is minimal, as their abundance in maize fields and the likelihood of encountering harmful amounts of pollen in and around maize MON 88017 fields are low. Non-target adult chrysomelids, which may occasionally feed on maize MON 88017 plants, are not expected to be affected due to the low activity of the Cry3Bb1 protein on adults. Impacts on NTOs caused by potential unintended changes in maize MON 88017 are not expected to occur, as no differences in composition, phenotypic characteristics and plant-NTO interactions were observed between maize MON 88017 and its near-isogenic line.
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Laboratory toxicity studies demonstrate no adverse effects of Cry1Ab and Cry3Bb1 to larvae of Adalia bipunctata (Coleoptera: Coccinellidae): the importance of study design
Transgenic Research, 2011Co-Authors: Fernando Álvarez-alfageme, Franz Bigler, Jorg RomeisAbstract:Scientific studies are frequently used to support policy decisions related to transgenic crops. Schmidt et al., Arch Environ Contam Toxicol 56:221–228 ( 2009 ) recently reported that Cry1Ab and Cry3Bb were toxic to larvae of Adalia bipunctata in direct feeding studies. This study was quoted, among others, to justify the ban of Bt maize (MON 810) in Germany. The study has subsequently been criticized because of methodological shortcomings that make it questionable whether the observed effects were due to direct toxicity of the two Cry proteins. We therefore conducted tritrophic studies assessing whether an effect of the two proteins on A. bipunctata could be detected under more realistic routes of exposure. Spider mites that had fed on Bt maize (events MON810 and MON88017) were used as carriers to expose young A. bipunctata larvae to high doses of biologically active Cry1Ab and Cry3Bb1. Ingestion of the two Cry proteins by A. bipunctata did not affect larval mortality, weight, or development time. These results were confirmed in a subsequent experiment in which A. bipunctata were directly fed with a sucrose solution containing dissolved purified proteins at concentrations approximately 10 times higher than measured in Bt maize-fed spider mites. Hence, our study does not provide any evidence that larvae of A. bipunctata are sensitive to Cry1Ab and Cry3Bb1 or that Bt maize expressing these proteins would adversely affect this predator. The results suggest that the apparent harmful effects of Cry1Ab and Cry3Bb1 reported by Schmidt et al., Arch Environ Contam Toxicol 56:221–228 ( 2009 ) were artifacts of poor study design and procedures. It is thus important that decision-makers evaluate the quality of individual scientific studies and do not view all as equally rigorous and relevant.
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Laboratory toxicity studies demonstrate no adverse effects of Cry1Ab and Cry3Bb1 to larvae of Adalia bipunctata (Coleoptera: Coccinellidae): the importance of study design
Transgenic Research, 2011Co-Authors: Fernando Álvarez-alfageme, Franz Bigler, Jorg RomeisAbstract:Scientific studies are frequently used to support policy decisions related to transgenic crops. Schmidt et al., Arch Environ Contam Toxicol 56:221–228 ( 2009 ) recently reported that Cry1Ab and Cry3Bb were toxic to larvae of Adalia bipunctata in direct feeding studies. This study was quoted, among others, to justify the ban of Bt maize (MON 810) in Germany. The study has subsequently been criticized because of methodological shortcomings that make it questionable whether the observed effects were due to direct toxicity of the two Cry proteins. We therefore conducted tritrophic studies assessing whether an effect of the two proteins on A. bipunctata could be detected under more realistic routes of exposure. Spider mites that had fed on Bt maize (events MON810 and MON88017) were used as carriers to expose young A. bipunctata larvae to high doses of biologically active Cry1Ab and Cry3Bb1. Ingestion of the two Cry proteins by A. bipunctata did not affect larval mortality, weight, or development time. These results were confirmed in a subsequent experiment in which A. bipunctata were directly fed with a sucrose solution containing dissolved purified proteins at concentrations approximately 10 times higher than measured in Bt maize-fed spider mites. Hence, our study does not provide any evidence that larvae of A. bipunctata are sensitive to Cry1Ab and Cry3Bb1 or that Bt maize expressing these proteins would adversely affect this predator. The results suggest that the apparent harmful effects of Cry1Ab and Cry3Bb1 reported by Schmidt et al., Arch Environ Contam Toxicol 56:221–228 ( 2009 ) were artifacts of poor study design and procedures. It is thus important that decision-makers evaluate the quality of individual scientific studies and do not view all as equally rigorous and relevant.
Aaron J. Gassmann - One of the best experts on this subject based on the ideXlab platform.
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Inheritance and Fitness Costs of Cry3Bb1 Resistance in Diapausing Field Strains of Western Corn Rootworm (Coleoptera: Chrysomelidae).
Journal of economic entomology, 2020Co-Authors: Ram B. Shrestha, Aaron J. GassmannAbstract:Field-evolved resistance to Cry3Bb1 corn by western corn rootworm, Diabrotica virgifera virgifera LeConte (Colleoptera: Chrysomellidae), has been reported in field populations in Iowa, Illinois, Nebraska, and Minnesota. Inheritance and fitness costs associated with Cry3Bb1 resistance have been determined for non-diapausing laboratory strains of western corn rootworm with either laboratory-selected resistance or field-derived resistance. However, information on inheritance and fitness costs of Cry3Bb1 resistance in the diapausing field populations is lacking. In this study, we determined the inheritance of Cry3Bb1 resistance for four diapausing field strains of western corn rootworm using plant-based bioassays. We also determined the fitness costs for eight diapausing field populations in a greenhouse experiment. We found that Cry3Bb1 resistance was an autosomal trait and that the inheritance of resistance was mostly non-recessive; however, there was some variation in the dominance of Cry3Bb1 resistance. We did not find evidence of fitness costs affecting survival to adulthood, developmental rate, or adult dry mass. However, we did detect a fitness cost affecting adult size. The results of this study will add to the current understanding of field-evolved resistance to Cry3Bb1 corn by western corn rootworm and help in developing better strategies to manage resistance.
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Applying a Selection Experiment to Test for Fitness Costs of Bt Resistance in Western Corn Rootworm (Coleoptera: Chrysomelidae) and the Effect of Density on Fitness Costs.
Journal of economic entomology, 2020Co-Authors: Coy R St. Clair, Ram B. Shrestha, Mike W. Dunbar, Eric H. Clifton, Kenneth E. Masloski, Aubrey R. Paolino, Aaron J. GassmannAbstract:Western corn rootworm, Diabrotica virgifera virgifera LeConte, is a serious pest of corn and is often managed with transgenic corn producing insecticidal toxins from the bacterium Bacillus thuringiensis (Bt). This pest has developed field-evolved resistance to all commercially available Bt traits, beginning with Cry3Bb1 in 2009. Fitness costs may accompany Bt resistance, where individuals with alleles for Bt resistance have reduced fitness on non-Bt corn compared to Bt-susceptible individuals. In conjunction with non-Bt refuges, fitness costs can delay the evolution of Bt resistance. Importantly, ecological factors may affect the presence and magnitude of fitness costs. For western corn rootworm, available data suggest that fitness costs of Bt resistance may be present in some cases. Using two Cry3Bb1-resistant western corn rootworm strains (Hopkinton and Cresco), a fitness-cost experiment was performed by rearing rootworm in the absence of Bt for six generations to test for fitness costs of Cry3Bb1 resistance and the effect of larval rearing density on fitness costs. Fitness costs were detected for both strains; however, strains were still resistant to Cry3Bb1 corn at the end of the experiment. Cresco experienced a greater loss of resistance at low versus high density, but no effect of density was detected in Hopkinton. Our study shows that fitness costs can accompany Bt resistance in western corn rootworm and may be more pronounced under low larval density. Even though fitness costs were present, it appears that rootworm populations may remain resistant to Cry3Bb1 corn for years after resistance has evolved.
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Western corn rootworm abundance, injury to corn, and resistance to Cry3Bb1 in the local landscape of previous problem fields.
PloS one, 2020Co-Authors: Coy R St. Clair, Graham P Head, Aaron J. GassmannAbstract:Western corn rootworm, Diabrotica virgifera virgifera LeConte (Coleoptera: Chrysomelidae), is a major pest of corn in the United States. Transgenic corn expressing insecticidal proteins derived from the bacterium Bacillus thuringiensis (Bt) is an important tool used to manage rootworm populations. However, field-evolved resistance to Bt threatens this technology. In areas where resistance is present, resistant individuals may travel from one field to a neighboring field, spreading resistance alleles. An important question that remains to be answered is the extent to which greater-than-expected root injury (i.e., >1 node of injury) to Cry3Bb1 corn from western corn rootworm is associated with rootworm abundance, root injury, and levels of resistance in neighboring fields. To address this question, fields with a history of greater-than-expected injury to Cry3Bb1 corn (focal fields) and surrounding fields (< 2.2 km from focal fields) were examined to quantify rootworm abundance, root injury, and resistance to Cry3Bb1 corn. Additionally, use of Bt corn and soil insecticide use for the previous six years were quantified for each field. Resistance to Cry3Bb1 was present in all fields assayed, even though focal fields had grown more Cry3 corn and less non-Bt corn than surrounding fields. This finding implies that some movement of resistance alleles had occurred between focal fields and surrounding fields. Overall, our data suggest that resistance to Cry3Bb1 in the landscape has been influenced by both local rootworm movement and field-level management tactics.
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Comparing Populations of Western Corn Rootworm (Coleoptera: Chrysomelidae) in Regions With and Without a History of Injury to Cry3 Corn.
Journal of economic entomology, 2020Co-Authors: Coy R St. Clair, Graham P Head, Aaron J. GassmannAbstract:Transgenic corn expressing insecticidal proteins derived from the bacterium Bacillus thuringiensis (Bt) is an important pest management tool. Western corn rootworm, Diabrotica virgifera virgifera LeConte, is a key pest of corn in the midwestern United States that has developed field-evolved resistance to all available Bt traits. The first Bt trait to be commercialized for management of rootworm was Cry3Bb1 in 2003, and field-evolved resistance appeared in 2009. In this study, we examined fields in counties where greater-than-expected injury to Cry3 (Cry3Bb1 or mCry3A) corn roots (>1 node) had previously been reported (problem counties) and counties where injury had not been reported (non-problem counties). Four to eight fields were sampled per county in 2015, 2016, and 2017 to quantify rootworm abundance, root injury, Cry3Bb1resistance, and rootworm management strategies. Rootworm abundance, root injury, and resistance to Cry3Bb1 did not differ between county types. Management tactics differed between county types, with problem counties growing more corn, using more soil insecticide, and growing more Cry34/35Ab1 corn. Additionally, a comparison of root injury to Bt and non-Bt corn within fields indicated that farmers derived an economic benefit from planting Bt corn to manage corn rootworm. Our results suggest that rootworm populations are similar between problem and non-problem counties in Iowa due to similar levels of selection pressure on Cry3 corn, but problem county fields have applied more management tactics due to previous rootworm issues in the area.
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Field and Laboratory Studies of Resistance to Bt Corn by Western Corn Rootworm (Coleoptera: Chrysomelidae).
Journal of economic entomology, 2019Co-Authors: Ram B. Shrestha, Aaron J. GassmannAbstract:Western corn rootworm, Diabrotica virgifera virgifera LeConte (Coleoptera: Chrysomelidae), has developed resistance to transgenic corn that produces the insecticidal toxin Cry3Bb1 derived from the bacterium Bacillus thuringiensis (Bacillales: Bacillaceae) (Bt), with cross-resistance extending to corn with Bt toxins mCry3A and eCry3.1Ab. Additionally, some populations of western corn rootworm have evolved resistance to Cry34/35Ab1 corn. We conducted a 2-yr field and laboratory study that included three field locations: 1) Bt-susceptible population, 2) field with a recent history of Cry3Bb1 resistance, and 3) field with a long-term history of Cry3Bb1 resistance. The population with recently evolved Cry3Bb1 resistance showed resistance to Cry3Bb1 corn in both laboratory bioassays and field evaluations; by contrast, the population with a long-term history of Cry3Bb1 resistance showed resistance, in both laboratory and field experiments to Cry3Bb1 corn and corn with a pyramid of mCry3A plus eCry3.1Ab corn. Field-based evaluations also showed that the field population with a long-term history of Cry3Bb1 resistance imposed higher root injury to Cry3Bb1 corn and the pyramid of mCry3A plus eCry3.1Ab compared with the susceptible control. The results of this study are discussed in the context of developing strategies to manage western corn rootworm in areas where populations have evolved resistance to Cry3Bb1 corn.
Michael Meissle - One of the best experts on this subject based on the ideXlab platform.
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Sensitivity of the cereal leaf beetle Oulema melanopus (Coleoptera: Chrysomelidae) to Bt maize-expressed Cry3Bb1 and Cry1Ab
Arthropod-Plant Interactions, 2012Co-Authors: Michael Meissle, Simon Knecht, Mario Waldburger, Jorg RomeisAbstract:The sensitivity of the cereal leaf beetle, Oulema melanopus (Coleoptera: Chrysomelidae), to maize-expressed Bacillus thuringiensis (Bt) proteins was investigated in the present study. Neonate larvae of O. melanopus were caged on leaves of Cry3Bb1-expressing (MON88017) or Cry1Ab-expressing (MON810) Bt maize, the corresponding near-isolines, or two non-related, conventional maize varieties. Larval survival was reduced on Cry3Bb1-expressing, but not on Cry1Ab-expressing maize compared with conventional varieties. Differences among conventional varieties were also present. The amount of eaten leaf material, developmental time to prepupal stage, and prepupal weight did not differ between Bt maize varieties and their corresponding near-isolines. In an additional feeding study with newly emerged adults, survival and beetle weight did not differ when leaves of Cry3Bb1-expressing maize or the near-isoline were offered as food over 3 weeks. ELISA measurements revealed that larvae feeding on Bt maize contained rather high Cry3Bb1 or Cry1Ab levels, which were in the same order of magnitude as the leaves. In contrast, concentrations in feces were one order, and concentrations in prepupae and adults two orders of magnitude lower.
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Impact of Cry3Bb1-expressing Bt maize on adults of the western corn rootworm, Diabrotica virgifera virgifera (Coleoptera: Chrysomelidae)
Pest management science, 2011Co-Authors: Michael Meissle, Richard L. Hellmich, Jorg RomeisAbstract:BACKGROUND: Genetically engineered maize producing insecticidal Cry3Bb1 protein fromBacillusthuringiensis (Bt )i s protected from root damage by corn rootworm larvae. An examination was made to establish whether western corn rootworm (Diabrotica virgiferavirgifera) adults are affected by Cry3Bb1-expressing maize (MON88017) when feeding on above-ground tissue. RESULTS: In laboratory bioassays, adult D. v. virgifera were fed for 7 weeks with silk, leaves or pollen from Bt maize or the corresponding near-isoline. Male, but not female, survival was reduced in the Bt-leaf treatment compared with the control. Female weight was lower when fed Bt maize, and egg production was reduced in the Bt-silk treatment. ELISA measurements demonstrated that beetles feeding on silk were exposed to higher Cry3Bb1 concentrations than beetles collected fromBt-maize fields in the United States. In contrast to silk and pollen, feeding on leaves resulted in high mortality and low fecundity. Females feeding on pollen produced more eggs than on silk. C : N ratios indicated that silk does not provide enough nitrogen for optimal egg production. CONCLUSIONS: Direct effects of Cry3Bb1 on adult beetles could explain the observed effects, but varietal differences between Bt and control maize are also possible. The impact of Bt maize on adult populations, however, is likely to be limited. c � 2011 Society of Chemical Industry
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Decomposition dynamics and structural plant components of genetically modified Bt maize leaves do not differ from leaves of conventional hybrids
Transgenic Research, 2010Co-Authors: Corinne Zurbrügg, Michael Meissle, Jorg Romeis, Linda Hönemann, Wolfgang NentwigAbstract:The cultivation of genetically modified Bt maize has raised environmental concerns, as large amounts of plant residues remain in the field and may negatively impact the soil ecosystem. In a field experiment, decomposition of leaf residues from three genetically modified (two expressing the Cry1Ab, one the Cry3Bb1 protein) and six non-transgenic hybrids (the three corresponding non-transformed near-isolines and three conventional hybrids) was investigated using litterbags. To elucidate the mechanisms that cause differences in plant decomposition, structural plant components (i.e., C:N ratio, lignin, cellulose, hemicellulose) were examined. Furthermore, Cry1Ab and Cry3Bb1 protein concentrations in maize leaf residues were measured from harvest to the next growing season. While leaf residue decomposition in transgenic and non-transgenic plants was similar, differences among conventional cultivars were evident. Similarly, plant components among conventional hybrids differed more than between transgenic and non-transgenic hybrids. Moreover, differences in senescent plant material collected directly from plants were larger than after exposure to soil for 5 months. While the concentration of Cry3Bb1 was higher in senescent maize leaves than that of Cry1Ab, degradation was faster, indicating that Cry3Bb1 has a shorter persistence in plant residues. As decomposition patterns of Bt -transgenic maize were shown to be well within the range of common conventional hybrids, there is no indication of ecologically relevant, adverse effects on the activity of the decomposer community.
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The web‐building spider Theridion impressum (Araneae: Theridiidae) is not adversely affected by Bt maize resistant to corn rootworms
Plant Biotechnology Journal, 2009Co-Authors: Michael Meissle, Jorg RomeisAbstract:The growth of genetically engineered maize that produces the insecticidal protein Cry3Bb1 from Bacillus thuringiensis (Bt) is an effective method to control corn rootworms (Diabrotica spp.), which are threatening maize production in North America and Europe. In this study, the risk of Cry3Bb1-expressing maize for the predatory spider Theridion impressum, a common species in European maize fields, was assessed. Quantification of Cry3Bb1 in potential prey species collected in Bt maize plots and prey spectrum analysis revealed that T. impressum ingests Cry3Bb1 in the field. Exposure to the Bt protein, however, was highly variable because some potential prey species, such as phloem-feeding herbivores and predators, contained little or no Cry3Bb1, whereas leaf-feeding herbivores contained high concentrations. Adult and juvenile T. impressum spiders were fed with Cry3Bb1-containing food (prey or maize pollen) for 8 weeks in the laboratory to examine the toxicity of the Bt protein. No differences in mortality, weight development or offspring production were observed between spiders provided with food containing or not containing Cry3Bb1. Retrospective power analysis indicated that the bioassays were sufficiently sensitive to detect meaningful differences if present. Although Cry3Bb1 is ingested by the spider in the field, our data provide no evidence for toxicity. Consequently, the growth of corn rootworm-resistant Bt maize appears to pose no risk for T. impressum.
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the web building spider theridion impressum araneae theridiidae is not adversely affected by bt maize resistant to corn rootworms
Plant Biotechnology Journal, 2009Co-Authors: Michael Meissle, Jorg RomeisAbstract:The growth of genetically engineered maize that produces the insecticidal protein Cry3Bb1 from Bacillus thuringiensis (Bt) is an effective method to control corn rootworms (Diabrotica spp.), which are threatening maize production in North America and Europe. In this study, the risk of Cry3Bb1-expressing maize for the predatory spider Theridion impressum, a common species in European maize fields, was assessed. Quantification of Cry3Bb1 in potential prey species collected in Bt maize plots and prey spectrum analysis revealed that T. impressum ingests Cry3Bb1 in the field. Exposure to the Bt protein, however, was highly variable because some potential prey species, such as phloem-feeding herbivores and predators, contained little or no Cry3Bb1, whereas leaf-feeding herbivores contained high concentrations. Adult and juvenile T. impressum spiders were fed with Cry3Bb1-containing food (prey or maize pollen) for 8 weeks in the laboratory to examine the toxicity of the Bt protein. No differences in mortality, weight development or offspring production were observed between spiders provided with food containing or not containing Cry3Bb1. Retrospective power analysis indicated that the bioassays were sufficiently sensitive to detect meaningful differences if present. Although Cry3Bb1 is ingested by the spider in the field, our data provide no evidence for toxicity. Consequently, the growth of corn rootworm-resistant Bt maize appears to pose no risk for T. impressum.
Graham P Head - One of the best experts on this subject based on the ideXlab platform.
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Western corn rootworm abundance, injury to corn, and resistance to Cry3Bb1 in the local landscape of previous problem fields.
PloS one, 2020Co-Authors: Coy R St. Clair, Graham P Head, Aaron J. GassmannAbstract:Western corn rootworm, Diabrotica virgifera virgifera LeConte (Coleoptera: Chrysomelidae), is a major pest of corn in the United States. Transgenic corn expressing insecticidal proteins derived from the bacterium Bacillus thuringiensis (Bt) is an important tool used to manage rootworm populations. However, field-evolved resistance to Bt threatens this technology. In areas where resistance is present, resistant individuals may travel from one field to a neighboring field, spreading resistance alleles. An important question that remains to be answered is the extent to which greater-than-expected root injury (i.e., >1 node of injury) to Cry3Bb1 corn from western corn rootworm is associated with rootworm abundance, root injury, and levels of resistance in neighboring fields. To address this question, fields with a history of greater-than-expected injury to Cry3Bb1 corn (focal fields) and surrounding fields (< 2.2 km from focal fields) were examined to quantify rootworm abundance, root injury, and resistance to Cry3Bb1 corn. Additionally, use of Bt corn and soil insecticide use for the previous six years were quantified for each field. Resistance to Cry3Bb1 was present in all fields assayed, even though focal fields had grown more Cry3 corn and less non-Bt corn than surrounding fields. This finding implies that some movement of resistance alleles had occurred between focal fields and surrounding fields. Overall, our data suggest that resistance to Cry3Bb1 in the landscape has been influenced by both local rootworm movement and field-level management tactics.
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Comparing Populations of Western Corn Rootworm (Coleoptera: Chrysomelidae) in Regions With and Without a History of Injury to Cry3 Corn.
Journal of economic entomology, 2020Co-Authors: Coy R St. Clair, Graham P Head, Aaron J. GassmannAbstract:Transgenic corn expressing insecticidal proteins derived from the bacterium Bacillus thuringiensis (Bt) is an important pest management tool. Western corn rootworm, Diabrotica virgifera virgifera LeConte, is a key pest of corn in the midwestern United States that has developed field-evolved resistance to all available Bt traits. The first Bt trait to be commercialized for management of rootworm was Cry3Bb1 in 2003, and field-evolved resistance appeared in 2009. In this study, we examined fields in counties where greater-than-expected injury to Cry3 (Cry3Bb1 or mCry3A) corn roots (>1 node) had previously been reported (problem counties) and counties where injury had not been reported (non-problem counties). Four to eight fields were sampled per county in 2015, 2016, and 2017 to quantify rootworm abundance, root injury, Cry3Bb1resistance, and rootworm management strategies. Rootworm abundance, root injury, and resistance to Cry3Bb1 did not differ between county types. Management tactics differed between county types, with problem counties growing more corn, using more soil insecticide, and growing more Cry34/35Ab1 corn. Additionally, a comparison of root injury to Bt and non-Bt corn within fields indicated that farmers derived an economic benefit from planting Bt corn to manage corn rootworm. Our results suggest that rootworm populations are similar between problem and non-problem counties in Iowa due to similar levels of selection pressure on Cry3 corn, but problem county fields have applied more management tactics due to previous rootworm issues in the area.
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Evaluation of SmartStax and SmartStax PRO maize against western corn rootworm and northern corn rootworm: efficacy and resistance management.
Pest management science, 2017Co-Authors: Graham P Head, D. M. Rule, Thomas L Clark, Matthew Carroll, Sean P Evans, Alan R. Willse, Nicholas P. Storer, Ronald Flannagan, Luke W Samuel, Lance J MeinkeAbstract:BACKGROUND Cases of western corn rootworm (WCR) field-evolved resistance to Cry3Bb1 and other corn rootworm (CRW) control traits have been reported. Pyramid products expressing multiple CRW traits can delay resistance compared to single trait products. We used field studies to assess the pyramid CRW corn products, SmartStax (expressing Cry3Bb1 and Cry34Ab1/Cry35Ab1) and SmartStax PRO (expressing Cry3Bb1, Cry34Ab1/Cry35Ab1 and DvSnf7), at locations with high WCR densities and possible Cry3Bb1 resistance, and to assess the reduction in adult emergence attributable to DvSnf7 and other traits. Insect resistance models were used to assess durability of SmartStax and SmartStax PRO to WCR resistance. RESULTS SmartStax significantly reduced root injury compared to non-CRW-trait controls at all but one location with measurable WCR pressure, while SmartStax PRO significantly reduced root injury at all locations, despite evidence of Cry3Bb1 resistance at some locations. The advantage of SmartStax PRO over SmartStax in reducing root damage was positively correlated with root damage on non-CRW-trait controls. DvSnf7 was estimated to reduce WCR emergence by approximately 80–95%, which modeling indicated will improve durability of Cry3Bb1 and Cry34Ab1/Cry35Ab1 compared to SmartStax. CONCLUSION The addition of DvSnf7 in SmartStax PRO can reduce root damage under high WCR densities and prolong Cry3Bb1 and Cry34Ab1/Cry35Ab1 durability. © 2017 Society of Chemical Industry
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Cry3Bb1 resistant western corn rootworm diabrotica virgifera virgifera leconte does not exhibit cross resistance to dvsnf7 dsrna
PLOS ONE, 2017Co-Authors: William Moar, Chitvan Khajuria, Michael Pleau, Oliver Ilagan, Mao Chen, Changjian Jiang, Paula A Price, Brian Mcnulty, Thomas L Clark, Graham P HeadAbstract:Background and Methodology There is a continuing need to express new insect control compounds in transgenic maize against western corn rootworm, Diabrotica virgifera virgifera (LeConte) (WCR). In this study three experiments were conducted to determine cross-resistance between the new insecticidal DvSnf7 dsRNA, and Bacillus thuringiensis (Bt) Cry3Bb1; used to control WCR since 2003, with field-evolved resistance being reported. Laboratory susceptible and Cry3Bb1-resistant WCR were evaluated against DvSnf7 dsRNA in larval diet-incorporation bioassays. Additionally, the susceptibility of seven field and one field-derived WCR populations to DvSnf7 (and Cry3Bb1) was assessed in larval diet-overlay bioassays. Finally, beetle emergence of laboratory susceptible and Cry3Bb1-resistant WCR was evaluated with maize plants in the greenhouse expressing Cry3Bb1, Cry34Ab1/Cry35Ab1, or DvSnf7 dsRNA singly, or in combination. Principal Findings and Conclusions The Cry3Bb1-resistant colony had slight but significantly (2.7-fold; P<0.05) decreased susceptibility to DvSnf7 compared to the susceptible colony, but when repeated using a field-derived WCR population selected for reduced Cry3Bb1 susceptibility, there was no significant difference (P<0.05) in DvSnf7 susceptibility compared to that same susceptible population. Additionally, this 2.7-fold difference in susceptibility falls within the range of DvSnf7 susceptibility among the seven field populations tested. Additionally, there was no correlation between susceptibility to DvSnf7 and Cry3Bb1 for all populations evaluated. In greenhouse studies, there were no significant differences (P<0.05) between beetle emergence of susceptible and Cry3Bb1-resistant colonies on DvSnf7 and Cry34Ab1/Cry35Ab1, and between DvSnf7 and MON 87411 (DvSnf7 + Cry3Bb1) for the Cry3Bb1-resistant colony. These results demonstrate no cross-resistance between DvSnf7 and Cry3Bb1 against WCR. Therefore, pyramiding DvSnf7 with Bt proteins such as Cry3Bb1 and Cry34Ab1/Cry35Ab1 will provide a valuable IRM tool against WCR that will increase the durability of these Bt proteins. These results also illustrate the importance of using appropriate bioassay methods when characterizing field-evolved resistant WCR populations.
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Cry3Bb1-Resistant Western Corn Rootworm, Diabrotica virgifera virgifera (LeConte) Does Not Exhibit Cross-Resistance to DvSnf7 dsRNA.
PloS one, 2017Co-Authors: William Moar, Chitvan Khajuria, Michael Pleau, Oliver Ilagan, Mao Chen, Changjian Jiang, Paula A Price, Brian Mcnulty, Thomas L Clark, Graham P HeadAbstract:Background and Methodology There is a continuing need to express new insect control compounds in transgenic maize against western corn rootworm, Diabrotica virgifera virgifera (LeConte) (WCR). In this study three experiments were conducted to determine cross-resistance between the new insecticidal DvSnf7 dsRNA, and Bacillus thuringiensis (Bt) Cry3Bb1; used to control WCR since 2003, with field-evolved resistance being reported. Laboratory susceptible and Cry3Bb1-resistant WCR were evaluated against DvSnf7 dsRNA in larval diet-incorporation bioassays. Additionally, the susceptibility of seven field and one field-derived WCR populations to DvSnf7 (and Cry3Bb1) was assessed in larval diet-overlay bioassays. Finally, beetle emergence of laboratory susceptible and Cry3Bb1-resistant WCR was evaluated with maize plants in the greenhouse expressing Cry3Bb1, Cry34Ab1/Cry35Ab1, or DvSnf7 dsRNA singly, or in combination. Principal Findings and Conclusions The Cry3Bb1-resistant colony had slight but significantly (2.7-fold; P
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fate of bacillus thuringiensis bt Cry3Bb1 protein in a soil microcosm
Chemosphere, 2008Co-Authors: Kelsey R Prihoda, Joel R CoatsAbstract:Transgenic crops expressing insecticidal, crystalline (Cry) Bacillus thuringiensis (Bt) proteins were commercialized in the US in 1996. There is little information in the peer-reviewed literature on the environmental fate of the coleopteran-active Bt Cry3Bb1 protein expressed in event MON863 corn. The exposure characterization of Bt proteins is unique in that the fate of the protein in soil and in crop residue must be considered. To date, the significance of macrodecomposing organisms, such as earthworms, isopods, and springtails, to the dissipation of Bt proteins present in crop residue has not been assessed. In addition, the input of Bt proteins into soil through leaching from post-harvest crop residue has not been examined. Two laboratory microcosm studies were conducted to determine the fate of Bt Cry3Bb1 in decomposing MON863 corn residue and to determine whether Bt proteins can enter soil by leaching from crop residue. In addition, the importance of macrodecomposing organisms to the degradation of Bt proteins in corn residue was assessed. Laboratory microcosms containing MON863 corn leaf, root, and stalk with and without macrodecomposers were used to examine the fate of Bt Cry3Bb1 in post-harvest MON863 corn residue. A half-life of less than five days was found for Bt Cry3Bb1 protein in decomposing MON863 corn residue. There was a trend of increasing half-life of Cry3Bb1 in microcosms containing macrodecomposers, however, this trend was only significant (p<0.05) for Bt Cry3Bb1 in MON863 leaf tissue and this increase is not likely relevant for non-target exposure. The recovery of Bt Cry3Bb1 protein from soil extracts was either below the limit of quantification (9 ng g(-1) soil) or below the limit of detection (0.7 ng mL(-1)) at all time points during the study. Based on the results from this study, Bt protein leaching from post-harvest crop residue is not a significant contributor to Bt protein input into soil.
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Fate of Bacillus thuringiensis (Bt) Cry3Bb1 protein in a soil microcosm.
Chemosphere, 2008Co-Authors: Kelsey R Prihoda, Joel R CoatsAbstract:Transgenic crops expressing insecticidal, crystalline (Cry) Bacillus thuringiensis (Bt) proteins were commercialized in the US in 1996. There is little information in the peer-reviewed literature on the environmental fate of the coleopteran-active Bt Cry3Bb1 protein expressed in event MON863 corn. The exposure characterization of Bt proteins is unique in that the fate of the protein in soil and in crop residue must be considered. To date, the significance of macrodecomposing organisms, such as earthworms, isopods, and springtails, to the dissipation of Bt proteins present in crop residue has not been assessed. In addition, the input of Bt proteins into soil through leaching from post-harvest crop residue has not been examined. Two laboratory microcosm studies were conducted to determine the fate of Bt Cry3Bb1 in decomposing MON863 corn residue and to determine whether Bt proteins can enter soil by leaching from crop residue. In addition, the importance of macrodecomposing organisms to the degradation of Bt proteins in corn residue was assessed. Laboratory microcosms containing MON863 corn leaf, root, and stalk with and without macrodecomposers were used to examine the fate of Bt Cry3Bb1 in post-harvest MON863 corn residue. A half-life of less than five days was found for Bt Cry3Bb1 protein in decomposing MON863 corn residue. There was a trend of increasing half-life of Cry3Bb1 in microcosms containing macrodecomposers, however, this trend was only significant (p
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Aquatic fate and effects of Bacillus thuringiensis Cry3Bb1 protein: toward risk assessment.
Environmental toxicology and chemistry, 2008Co-Authors: Kelsey R Prihoda, Joel R CoatsAbstract:Genetically engineered crops expressing Bacillus thuringiensis (Bt) insecticidal crystalline (Cry) proteins became commercially available in the United States in 1996. In 2006, 19 million ha of Bt corn were planted worldwide, which represents a 10 million ha increase in 10 years. The sustainability of Bt crops is important, because their use has significantly reduced the amount of chemical insecticides necessary to control agricultural pests. Despite the high adoption rates of this novel insecticide, little is known about the aquatic fate of transgenic Bt proteins and their nontarget effects on aquatic invertebrates, although several potential routes exist for their transport to aquatic systems. Methods were developed to investigate the aquatic fate of transgenic Bt proteins and to determine their potential effects on nontarget aquatic invertebrates. Laboratory microcosms containing pond water only or pond water and sediment were used to examine the fate of the coleopteran-active Bt Cry3Bb1 protein in decomposing transgenic corn event MON863 (hereafter referred to as MON863 corn) leaf, stalk, and root. A half-life of less than 3 d was found for Bt Cry3Bb1 from decomposing MON863 corn residue. No Bt Cry3Bb1 was measured in the pond water or sediment extracts of microcosms containing MON863 corn. In an acute, static, partial-renewal toxicity test, Bt Cry3Bb1 protein from MON863 root extracts was fed to Chironomus dilutus larvae for 10 d. A significant decrease in C. dilutus survival at nominal concentrations of 30 ng/ml was found; however, no effect on growth among the surviving larvae was observed.