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Reisig D, Heiniger R. Yield analysis and corn earworm feeding in Bt and non-Bt corn hybrids across diverse locations. JOURNAL OF ECONOMIC ENTOMOLOGY 2024:toae120. [PMID: 38832396 DOI: 10.1093/jee/toae120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/15/2024] [Revised: 05/01/2024] [Accepted: 05/17/2024] [Indexed: 06/05/2024]
Abstract
Corn, Zea mays L. (Poales: Poaceae), growers in the US Cotton Belt are required to plant 20% of total corn acres to non-Bt hybrids for resistance management (non-Bt refuge). Most growers do not meet this requirement, in part, because they perceive non-Bt hybrids to yield less than Bt hybrids. We planted multiple non-Bt and Bt hybrids from a single company in small-plot replicated trials at a single location from 2019 to 2023, as well as in small-plot replicated trials at multiple locations during 2022 and 2023. In the single location, we measured kernel injury from corn earworm, Helicoverpa zea Boddie (Lepidoptera: Noctuidae), and we recorded yield at all locations. In the single location trial, yields only separated among hybrids in 3 out of 5 years. In the multiple location trial, yields were variable between both years. We found that Bt hybrids tended to yield higher than non-Bt hybrids overall, but this was influenced by the inclusion of non-Bt hybrids that had a lower overall genetic yield potential in the environments we tested them in. In both tests, when hybrids were analyzed during each year, both Bt and non-Bt hybrids were among the statistically highest yielders. Our study demonstrates the importance of comparing multiple Bt and non-Bt hybrids to draw yield comparisons. This highlights the need for corn seed company breeders to put effort into improving yield for non-Bt hybrids. Hopefully this effort will translate into increased planting of non-Bt refuge corn for growers in the US Cotton Belt.
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Affiliation(s)
- Dominic Reisig
- Department of Entomology and Plant Pathology, NC State University, 207 Research Station Road, Plymouth, NC 27962, USA
| | - Ryan Heiniger
- Department of Crop and Soil Sciences, NC State University, Nelson Hall, 3709 Hillsboro Street, Raleigh, NC 27607, USA
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2
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Pezzini D, Taylor KL, Reisig DD, Fritz ML. Cross-pollination in seed-blended refuge and selection for Vip3A resistance in a lepidopteran pest as detected by genomic monitoring. Proc Natl Acad Sci U S A 2024; 121:e2319838121. [PMID: 38513093 PMCID: PMC10990109 DOI: 10.1073/pnas.2319838121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2023] [Accepted: 12/13/2023] [Indexed: 03/23/2024] Open
Abstract
The evolution of pest resistance to management tools reduces productivity and results in economic losses in agricultural systems. To slow its emergence and spread, monitoring and prevention practices are implemented in resistance management programs. Recent work suggests that genomic approaches can identify signs of emerging resistance to aid in resistance management. Here, we empirically examined the sensitivity of genomic monitoring for resistance management in transgenic Bt crops, a globally important agricultural innovation. Whole genome resequencing of wild North American Helicoverpa zea collected from non-expressing refuge and plants expressing Cry1Ab confirmed that resistance-associated signatures of selection were detectable after a single generation of exposure. Upon demonstrating its sensitivity, we applied genomic monitoring to wild H. zea that survived Vip3A exposure resulting from cross-pollination of refuge plants in seed-blended plots. Refuge seed interplanted with transgenic seed exposed H. zea to sublethal doses of Vip3A protein in corn ears and was associated with allele frequency divergence across the genome. Some of the greatest allele frequency divergence occurred in genomic regions adjacent to a previously described candidate gene for Vip3A resistance. Our work highlights the power of genomic monitoring to sensitively detect heritable changes associated with field exposure to Bt toxins and suggests that seed-blended refuge will likely hasten the evolution of resistance to Vip3A in lepidopteran pests.
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Affiliation(s)
- Daniela Pezzini
- Department of Entomology and Plant Pathology, North Carolina State University, Raleigh, NC27513
| | - Katherine L. Taylor
- Department of Entomology and Plant Pathology, North Carolina State University, Raleigh, NC27513
- Department of Entomology, University of Maryland, College Park, MD20742
| | - Dominic D. Reisig
- Department of Entomology and Plant Pathology, North Carolina State University, Raleigh, NC27513
| | - Megan L. Fritz
- Department of Entomology and Plant Pathology, North Carolina State University, Raleigh, NC27513
- Department of Entomology, University of Maryland, College Park, MD20742
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Kennedy H, Kerns DL, Head GP, Yang F. Cross-resistance and redundant killing of Vip3Aa resistant populations of Helicoverpa zea on purified Bt proteins and pyramided Bt crops. PEST MANAGEMENT SCIENCE 2023; 79:5173-5179. [PMID: 37575031 DOI: 10.1002/ps.7720] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/14/2023] [Revised: 08/04/2023] [Accepted: 08/14/2023] [Indexed: 08/15/2023]
Abstract
BACKGROUND Pyramiding Bt proteins is a key strategy to delay insect resistance development. However, the durability of pyramided Bt crops for controlling insect pests is threatened by cross-resistance among Bt proteins, which can ultimately contribute to resistance development. The corn earworm, Helicoverpa zea, is a major agricultural pest of pyramided Bt crops. Previous studies have examined cross-resistance and redundant killing of Cry resistance in H. zea, but such information is lacking for Vip3Aa resistance in this pest. Here, we evaluated cross-resistance and redundant killing of Vip3Aa-resistant H. zea to purified Bt proteins, as well as Bt corn and Bt cotton. RESULTS Diet bioassays demonstrated high susceptibility of Vip3Aa-resistant H. zea to Cry1Ac, Cry1A.105, and Cry2Ab2 purified proteins. No Vip3Aa-susceptible, -heterozygous, or -resistant H. zea could survive on pyramided Bt corn containing Cry1 and/or Cry2 proteins. Complete redundant killing was observed in pyramided Bt corn containing Cry1 and/or Cry2 proteins against Vip3Aa resistance in H. zea. Vip3Aa-susceptible, -heterozygous, and -resistant H. zea exhibited survival rates ranging from 0.0% to 22.5% on pyramided Bt cotton with Cry1 and/or Cry2 proteins. Incomplete to complete redundant killing was observed for Vip3Aa-resistant H. zea on pyramided Bt cotton containing Cry1 and/or Cry2 proteins. CONCLUSION Our findings indicate that Vip3Aa-resistant H. zea does not exhibit positive cross-resistance to Cry1 or Cry2 proteins. In addition, most pyramided Bt crops showed complete or nearly complete redundant killing of Vip3Aa-resistant H. zea. These results indicate that a pyramiding strategy would often be effective for managing Vip3Aa resistance in regions of the United States where H. zea has not evolved resistance to Cry1 and Cry2 toxins. © 2023 Society of Chemical Industry.
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Affiliation(s)
- Haley Kennedy
- Department of Entomology, Texas A&M University, College Station, TX, USA
| | - David L Kerns
- Department of Entomology, Texas A&M University, College Station, TX, USA
| | | | - Fei Yang
- Department of Entomology, Texas A&M University, College Station, TX, USA
- Department of Entomology, University of Minnesota, Saint Paul, MN, USA
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Pezzini DT, Reisig DD, Buntin GD, Del Pozo-Valdivia AI, Gould F, Paula-Moraes SV, Reay-Jones FP. Impact of seed blend and structured maize refuge on Helicoverpa zea (Lepidoptera: Noctuidae) potential phenological resistance development parameters in pupae and adults. PEST MANAGEMENT SCIENCE 2023; 79:3493-3503. [PMID: 37139844 DOI: 10.1002/ps.7529] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/23/2022] [Revised: 04/29/2023] [Accepted: 05/04/2023] [Indexed: 05/05/2023]
Abstract
BACKGROUND Helicoverpa zea, an economic pest in the south-eastern United States, has evolved practical resistance to Bacillus thuringiensis (Bt) Cry toxins in maize and cotton. Insect resistance management (IRM) programs have historically required planting of structured non-Bt maize, but because of its low adoption, the use of seed blends has been considered. To generate knowledge on target pest biology and ecology to help improve IRM strategies, nine field trials were conducted in 2019 and 2020 in Florida, Georgia, North Carolina, and South Carolina to evaluate the impact of Bt (Cry1Ab + Cry1F or Cry1Ab + Cry1F + Vip3A) and non-Bt maize plants in blended and structured refuge treatments on H. zea pupal survival, weight, soil pupation depth, adult flight parameters, and adult time to eclosion. RESULTS From a very large sample size and geography, we found a significant difference in pupal mortality and weight among treatments in seed blends with Vip3A, implying that cross-pollination occurred between Bt and non-Bt maize ears. There was no treatment effect for pupation depth, adult flight distance, and eclosion time. CONCLUSION Results of this study demonstrate the potential impact of different refuge strategies on phenological development and survival of an important pest species of regulatory concern. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.
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Affiliation(s)
- Daniela T Pezzini
- Department of Entomology and Plant Pathology, North Carolina State University, Raleigh, NC, USA
| | - Dominic D Reisig
- Department of Entomology and Plant Pathology, North Carolina State University, Vernon G. James Research and Extension Center, Plymouth, NC, USA
| | - G David Buntin
- Department of Entomology, University of Georgia - Griffin Campus, Griffin, GA, USA
| | - Alejandro I Del Pozo-Valdivia
- Department of Entomology, Hampton Roads Agricultural Research and Extension Center, Virginia Polytechnic Institute and State University, Virginia Beach, VA, USA
| | - Fred Gould
- Department of Entomology and Plant Pathology, North Carolina State University, Raleigh, NC, USA
| | - Silvana V Paula-Moraes
- Entomology and Nematology Department, West Florida Research and Education Center, University of Florida, Jay, FL, USA
| | - Francis Pf Reay-Jones
- Department of Plant and Environmental Sciences, Clemson University, Florence, SC, USA
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Montezano DG, Hunt TE, Colombo da Luz PM, Karnik K, Kachman SD, Vélez AM, Peterson JA. Movement of Striacosta albicosta (Smith) (Lepidoptera: Noctuidae) Larvae on Transgenic Bt and Non- Bt Maize. INSECTS 2023; 14:524. [PMID: 37367340 DOI: 10.3390/insects14060524] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/07/2023] [Revised: 05/18/2023] [Accepted: 05/31/2023] [Indexed: 06/28/2023]
Abstract
Exposure of lepidopteran pests to Bacillus thuringiensis (Bt) proteins has been shown to affect the behavior of larvae, including increased movement and avoidance of Bt-expressing plants or diet. Therefore, we hypothesized that the behavior of western bean cutworm, Striacosta albicosta (Smith) (Lepidoptera: Noctuidae), an important pest of maize, could be affected when exposed to Bt plants. To test this hypothesis, we conducted a series of artificial arena and on-plant experiments to determine S. albicosta neonate behavior when exposed to Bt and non-Bt plant tissue. Video tracking experiments presented neonate larvae with the choice of Bt or non-Bt pollen in a Petri dish for 15 min while being video recorded for analysis with EthoVision software. This study showed an increase in mean velocity and total time spent moving for larvae in the presence of Cry1F vs. non-Bt when compared with Vip3A vs. non-Bt or Cry1F vs. Vip3A. However, there was no difference in total distance moved or time spent in the food zone for all scenarios. Maize tissue choice experiments allowed neonatal larvae the choice of feeding on Bt or non-Bt tassel or leaves for 9 h in Petri dish arenas. This experiment showed that larvae preferred tassel tissue over leaves but did not indicate that larvae could distinguish between Bt and non-Bt tissue. In contrast, on-plant experiments (including a whole plant neonate dispersal study under controlled conditions and an in-field silking behavior experiment) indicated that the presence of Cry1F and Vip3A Bt toxins increased plant abandonment, suggesting that larvae are able to detect and avoid Bt toxins. The discrepancy of these results is likely due to the on-plant studies providing more field-realistic environmental conditions and a longer duration of exposure to Bt toxins for the behavioral experiments. Our results represent the first steps in understanding the complex behavior of S. albicosta when exposed to Bt plants. A better understanding of the response of larvae when exposed to Bt traits can aid in the management of this pest, particularly for the design of resistance management strategies and refuge design.
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Affiliation(s)
- Débora G Montezano
- Department of Entomology, University of Nebraska-Lincoln, Lincoln, NE 68503, USA
| | - Thomas E Hunt
- Haskell Agricultural Laboratory, Department of Entomology, University of Nebraska-Lincoln, Concord, NE 68728, USA
| | - Priscila M Colombo da Luz
- West Central Research, Extension & Education Center, Department of Entomology, University of Nebraska-Lincoln, North Platte, NE 69101, USA
| | - Kelsey Karnik
- Department of Statistics, University of Nebraska-Lincoln, Lincoln, NE 68588, USA
| | - Stephen D Kachman
- Department of Statistics, University of Nebraska-Lincoln, Lincoln, NE 68588, USA
| | - Ana M Vélez
- Department of Entomology, University of Nebraska-Lincoln, Lincoln, NE 68503, USA
| | - Julie A Peterson
- West Central Research, Extension & Education Center, Department of Entomology, University of Nebraska-Lincoln, North Platte, NE 69101, USA
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Lin S, Head G, Price P, Niu Y, Huang F. Relative fitness of susceptible and Cry1A.105/Cry2Ab2-single-/dual-protein-resistant Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae) on non-Bt diet and a diet containing a low concentration of two proteins. INSECT SCIENCE 2023; 30:398-410. [PMID: 35670378 DOI: 10.1111/1744-7917.13087] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/23/2022] [Revised: 05/22/2022] [Accepted: 05/26/2022] [Indexed: 06/15/2023]
Abstract
Helicoverpa zea (Boddie) is a destructive agricultural pest species that is targeted by both Bacillus thuringiensis (Bt) maize and cotton in the United States. Cry1A.105 and Cry2Ab2 are two Bt proteins expressed in a widely planted maize event MON 89034. In this study, two tests (Test-I and Test-II) were conducted to evaluate the relative fitness of Bt-susceptible and -resistant H. zea on non-Bt diet (Test-I and Test-II) and a diet containing a mix of Cry1A.105 and Cry2Ab2 at a low concentration (Test-II only). Insect populations evaluated in Test-I were two Bt-susceptible strains and three Bt-resistant strains (a single-protein Cry1A.105-, a single-protein Cry2Ab2-, and a dual-protein Cry1A.105/Cry2Ab2-resistant strains). Test-II analyzed the same two susceptible strains, three backcrossed-and-reselected Cry1A.105/Cry2Ab2-single-/dual-protein-resistant strains, and three F1 heterozygous strains. Measurements of life table parameters showed that neither the single- nor dual-protein Cry1A.105/Cry2Ab2 resistance in H. zea was associated with fitness costs under the test conditions. The single Cry protein resistances at a concentration of a mix of Cry1A.105 and Cry2Ab2 that resulted in a zero net reproductive rate for the two susceptible strains were functionally incomplete recessive or codominant, and the dual-protein resistance was completely dominant. The lack of fitness costs could be a factor contributing to the rapid revolution of resistance to the Cry proteins in this species. Data generated from this study should aid our understanding of Cry protein resistance evolution and help in refining IRM programs for H. zea.
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Affiliation(s)
- Shucong Lin
- Department of Entomology, Louisiana State University Agricultural Center, Baton Rouge, Louisiana, USA
| | - Graham Head
- Bayer Crop Science, Chesterfield, Missouri, USA
| | - Paula Price
- Bayer Crop Science, Chesterfield, Missouri, USA
| | - Ying Niu
- Department of Entomology, Louisiana State University Agricultural Center, Baton Rouge, Louisiana, USA
| | - Fangneng Huang
- Department of Entomology, Louisiana State University Agricultural Center, Baton Rouge, Louisiana, USA
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Santiago-González JC, Kerns DL, Head GP, Yang F. Effective dominance and redundant killing of single- and dual-gene resistant populations of Helicoverpa zea on pyramided Bt corn and cotton. PEST MANAGEMENT SCIENCE 2022; 78:4333-4339. [PMID: 35750998 DOI: 10.1002/ps.7052] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2022] [Revised: 06/13/2022] [Accepted: 06/24/2022] [Indexed: 06/15/2023]
Abstract
BACKGROUND Pyramided Bacillus thuringiensis (Bt) crops producing multiple Bt proteins with different modes of action are widely planted in the United States. Helicoverpa zea is a major target pest of pyramided Bt crops and has evolved practical resistance to both Cry1 and Cry2 proteins in some regions of U.S. However, little information is available regarding redundant killing and the dominance of resistance for insects possessing multiple resistance on pyramided Bt crops. In this study, we evaluated redundant killing and the dominance of resistance for H. zea strains resistant to Cry1 or Cry1 + Cry2 on pyramided Bt corn and cotton. RESULTS We found that the Cry1-resistant H. zea was incompletely dominant on Cry1Ac + Cry1F cotton. Pyramided crops producing Cry2 and/or Vip3Aa proteins showed a complete redundant killing against the Cry1-resistant H. zea. The Cry1 + Cry2-resistant H. zea displayed incompletely recessive to completely dominant resistance on pyramided Bt crops containing Cry1 and/or Cry2 proteins. The redundant killing was complete for the Cry1 + Cry2-resistant H. zea on pyramided Bt crops producing Vip3Aa protein. CONCLUSION The dominant resistance of Cry1 and Cry2 in H. zea on pyramided Bt crops deviates from the assumption of functionally recessive resistance underlying the high-dose refuge strategy. However, the assumptions of complete redundant killing are achieved for both Cry1- and Cry1 + Cry2-resistant H. zea on pyramided Bt crops. These results suggest that the pyramided strategy could be valuable for increasing the durability of Bt technology for managing H. zea, a pest with inherently low susceptibility against Cry proteins. © 2022 Society of Chemical Industry.
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Affiliation(s)
| | - David L Kerns
- Department of Entomology, Texas A&M University, College Station, TX, USA
| | | | - Fei Yang
- Department of Entomology, Texas A&M University, College Station, TX, USA
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8
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Yu W, Head GP, Huang F. Inheritance of Resistance to Cry1A.105 in Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae). INSECTS 2022; 13:875. [PMID: 36292823 PMCID: PMC9604160 DOI: 10.3390/insects13100875] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/20/2022] [Revised: 09/20/2022] [Accepted: 09/23/2022] [Indexed: 06/16/2023]
Abstract
Cry1A.105 is a bioengineered Bacillus thuringiensis (Bt) insecticidal protein consisting of three domains derived from Cry1Ac, Cry1Ab, and Cry1F. It is one of the two pyramided Bt toxins expressed in the MON 89034 event, a commonly planted Bt maize trait in the Americas. Recent studies have documented that field resistance of the corn earworm, Helicoverpa zea (Boddie), to the Cry1A.105 toxin in maize plants has become widespread in the United States. To investigate the inheritance of resistance to Cry1A.105 in H. zea, two independent tests, each with various genetic crosses among susceptible and Cry1A.105-resistant populations, were performed. The responses of these susceptible, resistant, F1, F2, and backcrossed insect populations to Cry1A.105 were assayed using a diet overlay method. The bioassays showed that the resistance to Cry1A.105 in H. zea was inherited as a single, autosomal, nonrecessive gene. The nonrecessive nature of the resistance could be an important factor contributing to the widespread resistance of maize hybrids containing Cry1A.105 in the United States. The results indicate that resistance management strategies for Bt crops need to be refined to ensure that they are effective in delaying resistance evolution for nonrecessive resistance (nonhigh dose).
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Affiliation(s)
- Wenbo Yu
- Department of Entomology, Louisiana State University Agricultural Center, Baton Rouge, LA 70803, USA
| | | | - Fangneng Huang
- Department of Entomology, Louisiana State University Agricultural Center, Baton Rouge, LA 70803, USA
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Yang F, Kennedy H, Santiago-González JC, Kerns DL. Effects of cross-pollination among non-Bt and pyramided Bt corn expressing cry proteins in seed mixtures on resistance development of dual-gene resistant Helicoverpa zea. PEST MANAGEMENT SCIENCE 2022; 78:3260-3265. [PMID: 35474413 DOI: 10.1002/ps.6945] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/21/2022] [Revised: 04/14/2022] [Accepted: 04/26/2022] [Indexed: 06/14/2023]
Abstract
BACKGROUND Seed mixture strategy can guarantee the compliance of planting non-Bt crops to host the susceptible insects for resistance management. However, pollen movement between Bt and non-Bt corn in the mixed plantings could reduce the efficacy of this strategy for ear-feeding insects. Few studies have evaluated the effects of cross-pollination among non-Bt and pyramided Bt corn in seed mixtures on the resistance development of insects possessing multiple resistances. Here, we provided the first study to investigate whether cross-pollination in mixed plantings of pyramided Bt corn producing Cry1A.105 and Cry2Ab2 would increase the dominance of resistance of dual-gene resistant populations of Helicoverpa zea, a target of pyramided Bt corn and cotton in the USA. RESULTS We compared the survival and development of susceptible, dual-gene resistant (resistance to both Cry1 and Cry2 proteins) and heterozygous genotypes of H. zea in the laboratory on non-Bt and pyramided Bt corn ears collected from mixed plantings and structured plantings in the field. We found higher fitness for F1 heterozygous insects than for the susceptible insects of H. zea on both pyramided Bt corn and non-Bt corn in the mixed plantings. CONCLUSION These results suggest that cross-pollination in mixed plantings will significantly increase the dominance of resistance by supporting survival of heterozygous insects for dual-gene resistant populations of H. zea, and therefore accelerate evolution of resistance to pyramided Bt crops. © 2022 Society of Chemical Industry.
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Affiliation(s)
- Fei Yang
- Department of Entomology, Texas A&M University, College Station, Texas, 77843-2475, USA
| | - Haley Kennedy
- Department of Entomology, Texas A&M University, College Station, Texas, 77843-2475, USA
| | | | - David L Kerns
- Department of Entomology, Texas A&M University, College Station, Texas, 77843-2475, USA
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10
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Arends BR, Reisig DD, Gundry S, Greene JK, Kennedy GG, Reay‐Jones FP, Huseth AS. Helicoverpa zea (Lepidoptera: Noctuidae) feeding incidence and survival on Bt maize in relation to maize in the landscape. PEST MANAGEMENT SCIENCE 2022; 78:2309-2315. [PMID: 35233922 PMCID: PMC9310716 DOI: 10.1002/ps.6855] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/22/2021] [Revised: 02/23/2022] [Accepted: 03/02/2022] [Indexed: 05/12/2023]
Abstract
BACKGROUND Characterizing Helicoverpa zea (Boddie) damage to maize (Zea mays L.) in relation to the spatiotemporal composition of Bt crops is essential to understand how landscape composition affects H. zea abundance. To examine this relationship, paired Bt (expressing Cry1A.105 + Cry2Ab2) and non-Bt maize plots were sampled across North and South Carolina during 2017-2019. Kernel damage and larval exit holes were measured following larval development. To understand how maize abundance surrounding sample sites related to feeding damage and larval development, we quantified maize abundance in a 1 km buffer surrounding the sample site and examined the relationship between local maize abundance and kernel damage and larval exit holes. RESULTS Across the years and locations, damage in Bt maize was widespread but significantly lower than in non-Bt maize, indicating that despite the widespread occurrence of resistance to Cry toxins in maize, Bt maize still provides a measurable reduction in damage. There were negative relationships between kernel injury and ears with larval exit holes in both Bt and non-Bt maize and the proportion of maize in the landscape during the current year. CONCLUSION Despite the widespread occurrence of resistance to Cry toxins in maize, this resistance is incomplete, and on average Bt maize continues to provide a measurable reduction in damage. We interpret the negative relationship between abundance of maize within 1 km of the sample location and maize infestation levels, as measured by kernel damage and larval exit holes, to reflect dispersion of the ovipositing moth population over available maize within the local landscape. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.
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Affiliation(s)
- Benjamin R. Arends
- Department of Entomology and Plant PathologyNorth Carolina State UniversityPlymouthNCUSA
| | - Dominic D. Reisig
- Department of Entomology and Plant PathologyNorth Carolina State UniversityPlymouthNCUSA
| | - Shawnee Gundry
- Department of Entomology and Plant PathologyNorth Carolina State UniversityPlymouthNCUSA
| | - Jeremy K. Greene
- Department of Plant and Environmental SciencesClemson University, Edisto Research and Education CenterBlackvilleSCUSA
| | - George G. Kennedy
- Department of Entomology and Plant PathologyNorth Carolina State UniversityRaleighNCUSA
| | - Francis P.F. Reay‐Jones
- Department of Plant and Environmental SciencesClemson University, Pee Dee Research and Education CenterFlorenceSCUSA
| | - Anders S. Huseth
- Department of Entomology and Plant PathologyNorth Carolina State UniversityPlymouthNCUSA
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Resistance Allele Frequency to Cry1Ab and Vip3Aa20 in Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae) in Louisiana and Three Other Southeastern U.S. States. Toxins (Basel) 2022; 14:toxins14040270. [PMID: 35448879 PMCID: PMC9028807 DOI: 10.3390/toxins14040270] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2022] [Revised: 03/31/2022] [Accepted: 04/02/2022] [Indexed: 01/27/2023] Open
Abstract
The corn earworm/bollworm, Helicoverpa zea (Boddie), is a pest species that is targeted by both Bacillus thuringiensis (Bt) maize and cotton in the United States. Cry1Ab and Vip3Aa20 are two common Bt toxins that are expressed in transgenic maize. The objective of this study was to determine the resistance allele frequency (RAF) to Cry1Ab and Vip3Aa20 in H. zea populations that were collected during 2018 and 2019 from four southeastern U.S. states: Louisiana, Mississippi, Georgia, and South Carolina. By using a group-mating approach, 104 F2 iso-lines of H. zea were established from field collections with most iso-lines (85) from Louisiana. These F2 iso-lines were screened for resistance alleles to Cry1Ab and Vip3Aa20, respectively. There was no correlation in larval survivorship between Cry1Ab and Vip3Aa20 when the iso-lines were exposed to these two toxins. RAF to Cry1Ab maize was high (0.256) and the RAFs were similar between Louisiana and the other three states and between the two sampling years. In contrast, no functional major resistance allele (RA) that allowed resistant insects to survive on Vip3Aa20 maize was detected and the expected RAF of major RAs with 95% probability was estimated to 0 to 0.0073. However, functional minor RAs to Vip3Aa20 maize were not uncommon; the estimated RAF for minor alleles was 0.028. The results provide further evidence that field resistance to Cry1Ab maize in H. zea has widely occurred, while major RAs to Vip3Aa20 maize are uncommon in the southeastern U.S. region. Information that was generated from this study should be useful in resistance monitoring and refinement of resistance management strategies to preserve Vip3A susceptibility in H. zea.
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Reisig DD, DiFonzo C, Dively G, Farhan Y, Gore J, Smith J. Best Management Practices to Delay the Evolution of Bt Resistance in Lepidopteran Pests Without High Susceptibility to Bt Toxins in North America. JOURNAL OF ECONOMIC ENTOMOLOGY 2022; 115:10-25. [PMID: 34922393 DOI: 10.1093/jee/toab247] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2021] [Indexed: 06/14/2023]
Abstract
Canadian and United States (US) insect resistance management (IRM) programs for lepidopteran pests in Bacillus thuriengiensis (Bt)-expressing crops are optimally designed for Ostrinia nubilalis Hübner in corn (Zea mays L.) and Chloridea virescens Fabricius in cotton (Gossypium hirsutum L.). Both Bt corn and cotton express a high dose for these pests; however, there are many other target pests for which Bt crops do not express high doses (commonly referred to as nonhigh dose pests). Two important lepidopteran nonhigh dose (low susceptibility) pests are Helicoverpa zea Boddie (Lepidoptera: Noctuidae) and Striacosta albicosta Smith (Lepidoptera: Noctuidae). We highlight both pests as cautionary examples of exposure to nonhigh dose levels of Bt toxins when the IRM plan was not followed. Moreover, IRM practices to delay Bt resistance that are designed for these two ecologically challenging and important pests should apply to species that are more susceptible to Bt toxins. The purpose of this article is to propose five best management practices to delay the evolution of Bt resistance in lepidopteran pests with low susceptibility to Bt toxins in Canada and the US: 1) better understand resistance potential before commercialization, 2) strengthen IRM based on regional pest pressure by restricting Bt usage where it is of little benefit, 3) require and incentivize planting of structured corn refuge everywhere for single toxin cultivars and in the southern US for pyramids, 4) integrate field and laboratory resistance monitoring programs, and 5) effectively use unexpected injury thresholds.
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Affiliation(s)
- Dominic D Reisig
- Department of Entomology and Plant Pathology, North Carolina State University, Vernon G. James Research and Extension Center, 207 Research Station Road, Plymouth, NC, 27962, USA
| | - Chris DiFonzo
- Department of Entomology, Michigan State University, 288 Farm Lane, East Lansing, MI, 48824, USA
| | - Galen Dively
- Department of Entomology, University of Maryland, College Park, MD, 20742, USA
| | - Yasmine Farhan
- Department of Plant Agriculture, University of Guelph Ridgetown Campus, 120 Main Street East, Ridgetown, ON, N0P 2C0, Canada
| | - Jeff Gore
- Department of Biochemistry, Molecular Biology, Entomology, and Plant Pathology, Mississippi State University, P.O. Box 197, Stoneville, MS, 38776, USA
| | - Jocelyn Smith
- Department of Plant Agriculture, University of Guelph Ridgetown Campus, 120 Main Street East, Ridgetown, ON, N0P 2C0, Canada
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Towles TB, Buntin GD, Catchot AL, Gore J, Cook DR, Caprio MA, Daves C. Quantifying the Contribution of Seed Blended Refugia in Field Corn to Helicoverpa zea (Lepidoptera: Noctuidae) Populations. JOURNAL OF ECONOMIC ENTOMOLOGY 2021; 114:1771-1778. [PMID: 34027979 DOI: 10.1093/jee/toab097] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/03/2021] [Indexed: 06/12/2023]
Abstract
Helicoverpa zea (Boddie), a pest of cotton that also occurs in field corn, is commonly controlled through the use of foliar-applied insecticides or transgenic crops expressing Bacillus thuringiensis (Berliner) (Bt) genes. To minimize the risk of Bt resistance in pest populations, refuge systems have been implemented for sustainable agroecosystem management. Historically, structured refuge compliance among growers has been low, leading to the commercialization of seed blended refugia. To test the viability of seed blended refugia in southern U.S. field corn, field studies were conducted in Mississippi and Georgia during 2016, 2017, and 2018 growing seasons. To quantify adult H. zea emergence from structured (non-Bt corn) and seed blended refuge options, emergence traps were utilized. Kernel damage among seed blended refuge and structured refuge corn ears were recorded and compared. The timing of moth emergence was recorded. When compared to a structured refuge, H. zea adult moth emergence from seed blended refugia did not significantly differ. Kernel damage of non-Bt plants in the seed blended treatments was not significantly different than non-Bt plants in the structured refuge treatments. Moth emergence timing was not significantly delayed between the structured refuge and seed blended refuge treatments. Results of this study suggest that a seed blended refuge may provide an effective insecticide resistance management alternative for H. zea in areas where structured refuge compliance is low.
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Affiliation(s)
- T B Towles
- Mississippi State University, Department of Biochemistry, Molecular Biology, Entomology, and Plant Pathology, Clay Lyle Entomology Building Room 110, Mississippi State, MS, USA
| | - G D Buntin
- Department of Entomology, University of Georgia - Griffin Campus, Griffin, GA, USA
| | - A L Catchot
- Mississippi State University, Department of Biochemistry, Molecular Biology, Entomology, and Plant Pathology, Clay Lyle Entomology Building Room 110, Mississippi State, MS, USA
| | - J Gore
- Mississippi State University, Delta Research and Extension Center, Stoneville, MS, USA
| | - D R Cook
- Mississippi State University, Delta Research and Extension Center, Stoneville, MS, USA
| | - M A Caprio
- Mississippi State University, Department of Biochemistry, Molecular Biology, Entomology, and Plant Pathology, Clay Lyle Entomology Building Room 110, Mississippi State, MS, USA
| | - C Daves
- Bayer Crop Science, St. Louis, MO, USA
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14
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Dimase M, Brown S, Head GP, Price PA, Walker W, Yu W, Huang F. Performance of Bt-susceptible and -heterozygous dual-gene resistant genotypes of Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) in seed blends of non-Bt and pyramided Bt maize. INSECT SCIENCE 2021; 28:1147-1158. [PMID: 32662592 DOI: 10.1111/1744-7917.12850] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/31/2020] [Revised: 07/06/2020] [Accepted: 07/07/2020] [Indexed: 05/28/2023]
Abstract
A seed blend refuge has been implemented in the U.S. Corn Belt for Bt maize resistance management. The fall armyworm, Spodoptera frugiperda (J.E. Smith), is a target pest of Bt maize in the Americas. The larvae of this pest are mobile, which may affect the efficacy of seed blend refuges. In this study, field and greenhouse trials were conducted to determine the performance of Bt-susceptible (aabb) and -heterozygous dual-gene-resistant (AaBb) genotypes of S. frugiperda in seed blends of non-Bt and pyramided Bt maize. Three field trials evaluated larval survival, larval growth, and plant injury with aabb in seed blends of Bt maize expressing Cry1A.105/Cry2Ab2/Vip3A with 0-30% non-Bt seeds. Greenhouse tests investigated the performance of aabb and AaBb in seed blends of Cry1A.105/Cry2Ab2 with 0-30% non-Bt seeds. In pure non-Bt maize plots, after 9-13 d of neonates being released on the plants, 0.39 and 0.65 larvae/plant survived with leaf injury ratings of 4.7 and 5.9 (Davis's 1-9 scale) in the field and greenhouse, respectively. In contrast, live larvae and plant injury were virtually not observed on Bt plants across all planting patterns. Larval occurrence and plant injury by aabb on non-Bt plants were similar between seed blends and pure non-Bt plantings, suggesting that the blended refuges could provide an equivalent susceptible population as structured refuge under the test conditions. In the greenhouse, the two insect genotypes in seed blends performed similarly, indicating that the seed blends did not provide more favorable conditions for AaBb over aabb. The information generated from this study should be useful in managing S. frugiperda and evaluating if send blends could be suitable refuge options for Bt resistance management in the regions where the insect is a primary target pest.
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Affiliation(s)
- Marcelo Dimase
- Department of Entomology, Louisiana State University Agricultural Center, Baton Rouge, Louisiana, USA
| | - Sebe Brown
- Dean Lee Research Station, Louisiana State University Agricultural Center, Alexandria, Louisiana, USA
| | | | | | - Wade Walker
- Macon Ridge Research Station, Louisiana State University Agricultural Center, Winnsboro, Louisiana, USA
| | - Wenbo Yu
- Department of Entomology, Louisiana State University Agricultural Center, Baton Rouge, Louisiana, USA
| | - Fangneng Huang
- Department of Entomology, Louisiana State University Agricultural Center, Baton Rouge, Louisiana, USA
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15
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Carrière Y, Degain BA, Tabashnik BE. Effects of gene flow between Bt and non-Bt plants in a seed mixture of Cry1A.105 + Cry2Ab corn on performance of corn earworm in Arizona. PEST MANAGEMENT SCIENCE 2021; 77:2106-2113. [PMID: 33350567 DOI: 10.1002/ps.6239] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/05/2020] [Revised: 12/08/2020] [Accepted: 12/17/2020] [Indexed: 06/12/2023]
Abstract
BACKGROUND Using natural populations of Helicoverpa zea from Arizona, we tested the hypotheses that gene flow between Bacillus thuringiensis (Bt) plants and non-Bt plants in a seed mixture of 10% non-Bt corn and 90% Bt corn producing Cry1A.105 and Cry2Ab reduces larval performance on ears from non-Bt plants, or increases performance on ears from Bt plants. RESULTS Gene flow was not detected in blocks of non-Bt or Bt corn but was extensive in seed mixtures. Analyses of larval weight and abundance over a period of 3 to 4 weeks did not indicate consistent effects of gene flow on development rate and survival. However for non-Bt plants, the ear area damaged and percentage of ears with exit holes were significantly lower in the seed mixtures than blocks. By contrast, the percentage of ears with exit holes and ear damage did not differ significantly between the seed mixtures and blocks for Bt plants. Nearly 100% of the ears were damaged and the damaged area was substantial, showing that H. zea is a major ear-feeding pest in Arizona. Relative to non-Bt corn, the pyramided Bt corn did not significantly reduce the percentage of damaged ears and only reduced the ear area damaged by 21 to 39%, indicating that H. zea may have evolved resistance to Cry1A.105, Cry2Ab, or both. CONCLUSIONS Our results indicate that gene flow between Bt and non-Bt plants in seed mixtures reduced effective refuge size, and that block refuges may be needed to manage the evolution of H. zea resistance to Bt corn in Arizona. © 2020 Society of Chemical Industry.
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Affiliation(s)
- Yves Carrière
- Department of Entomology, University of Arizona, Tucson, AZ, USA
| | - Ben A Degain
- Department of Entomology, University of Arizona, Tucson, AZ, USA
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16
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Extended investigation of field-evolved resistance of the corn earworm Helicoverpa zea(Lepidoptera: Noctuidae) to Bacillus thuringiensis Cry1A.105 and Cry2Ab2 proteins in thesoutheastern United States. J Invertebr Pathol 2021; 183:107560. [PMID: 33631194 DOI: 10.1016/j.jip.2021.107560] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2020] [Revised: 01/30/2021] [Accepted: 02/12/2021] [Indexed: 12/17/2022]
Abstract
Previous studies have reported that the corn earworm/bollworm, Helicoverpa zea (Boddie), has developed field resistance to pyramided Bacillus thuringiensis (Bt) Cry1A/Cry2A maize and cotton in certain areas of the southeastern United States. The objective of the current study was to determine the current status and distribution of the resistance to Cry1A.105 and Cry2Ab2 in H. zea. In the study, 31 H. zea populations were collected from major maize planting areas across seven southeastern states of the United States during 2018 and 2019 and assayed against the two Bt proteins. Diet over-lay bioassays showed that most of the populations collected during the two years were significantly resistant to the Cry1A.105 protein. Most of the populations collected during 2019 were also resistant to Cry2Ab2, while significant variances were observed in the susceptibility of the populations collected during 2018 to Cry2Ab2. The results showed that Cry1A.105 and Cry2Ab2 resistance in H. zea is widely distributed in the regions sampled. The resistance to Cry1A.105 appeared to have plateaued, while selection for Cry2Ab2 resistance is likely still occurring. Thus, effective measures for mitigating the Cry1A/Cry2A resistance need to be developed and implemented to ensure the sustainable use of Bt crop biotechnology.
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17
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Carrière Y, Degain BA, Harpold VS, Unnithan GC, Tabashnik BE. Gene Flow Between Bt and Non-Bt Plants in a Seed Mixture Increases Dominance of Resistance to Pyramided Bt Corn in Helicoverpa zea (Lepidoptera: Noctuidae). JOURNAL OF ECONOMIC ENTOMOLOGY 2020; 113:2041-2051. [PMID: 32582955 DOI: 10.1093/jee/toaa138] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/24/2020] [Indexed: 06/11/2023]
Abstract
For delaying evolution of pest resistance to transgenic corn producing Bacillus thuringiensis (Bt) toxins, limited data are available to compare the effectiveness of refuges of non-Bt corn planted in seed mixtures versus blocks. Here we addressed this issue in the ear-feeding pest Helicoverpa zea Boddie by measuring its survival and development in the laboratory on ears from field plots with 90% Cry1A.105 + Cry2Ab corn and 10% non-Bt corn planted in a seed mixture or blocks. We compared a strain of H. zea selected for resistance to Cry1Ac in the laboratory, its parent strain not selected in the laboratory, and their F1 progeny. The relative survival of the F1 progeny and dominance of resistance were higher on ears from Bt plants in the seed mixture than the block. Half of the kernels in ears from non-Bt plants in the seed mixture produced both Cry1A.105 and Cry2Ab. However, survival on ears from non-Bt plants did not differ between the block and seed mixture. In simulations based on the observed survival, resistance to Cry1A.105 + Cry2Ab corn evolved faster with the seed mixture than the blocks, because of the higher dominance of resistance in the seed mixture. Increasing the refuge percentage improved durability of Cry1A.105 + Cry2Ab corn more for the blocks than the seed mixture. These findings imply that, for a given percentage of non-Bt corn, resistance of H. zea and other ear-feeding pests to multi-toxin Bt corn is likely to evolve faster for seed mixtures than blocks.
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Affiliation(s)
- Yves Carrière
- Department of Entomology, University of Arizona, Tucson, AZ
| | - Ben A Degain
- Department of Entomology, University of Arizona, Tucson, AZ
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18
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Farhan Y, Smith JL, Limay-Rios V, Schaafsma AW. The Effect of Simulated Lepidopteran Ear Feeding Injury on Mycotoxin Accumulation in Grain Corn (Poales: Poaceae). JOURNAL OF ECONOMIC ENTOMOLOGY 2020; 113:2187-2196. [PMID: 32865199 DOI: 10.1093/jee/toaa174] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/15/2020] [Indexed: 06/11/2023]
Abstract
Fusarium graminearum Schwabe (Hypocreales: Nectriaceae) and Fusarium verticillioides (Saccardo) (Hypocreales: Nectriaceae) Nirenberg infection results in accumulation of deoxynivalenol (DON), zearalenone (ZON), and fumonisin (FBs) mycotoxins in infected corn, Zea mays L. Lepidopteran insect feeding may exacerbate fungal infection by providing entry points on the ear resulting in increased mycotoxin contamination of grain. The objective of the current study was to simulate different types and severity levels (extent of injury) of lepidopteran injury to corn ears at different stages of ear development and its effect on mycotoxin accumulation in grain corn. Field experiments were conducted under conditions favorable for F. graminearum development where insect injury was simulated to corn ears and inoculated with F. graminearum. All simulated injury treatments resulted in elevated mycotoxin concentration compared with ears without simulated injury; however, the severity of injury within a treatment had little effect. Injury to kernels on the side of the ear resulted in greater DON and ZON concentration than injury to tip kernels, grazing injury applied at physiological maturity, or when no injury was simulated. Greater FBs was measured when tip kernel injury was simulated at the blister stage or when side kernel injury was simulated at milk and dent stages compared with noninjured ears, silk clipping, tip injury at milk and dent stages, or grazing injury at physiological maturity. The current study confirms that the risk of mycotoxin accumulation in the Great Lakes region is greater in the presence of ear-feeding insect pests and may differ depending on the feeding behavior of pest species.
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Affiliation(s)
- Yasmine Farhan
- University of Guelph, Ridgetown Campus, Ridgetown, Ontario, Canada
| | - Jocelyn L Smith
- University of Guelph, Ridgetown Campus, Ridgetown, Ontario, Canada
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19
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Coates BS, Abel CA, Swoboda-Bhattarai KA, Palmquist DE, Montezano DG, Zukoff SN, Wang Y, Bradshaw JD, DiFonzo CD, Shields E, Tilmon KJ, Hunt TE, Peterson JA. Geographic Distribution of Bacillus thuringiensis Cry1F Toxin Resistance in Western Bean Cutworm (Lepidoptera: Noctuidae) Populations in the United States. JOURNAL OF ECONOMIC ENTOMOLOGY 2020; 113:2465-2472. [PMID: 32740653 DOI: 10.1093/jee/toaa136] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/29/2020] [Indexed: 06/11/2023]
Abstract
The western bean cutworm (WBC), Striacosta albicosta (Lepidoptera: Noctuidae), can be a severe pest of transgenic corn in the western Plains and Great Lakes regions of North America, including on hybrids expressing the Bacillus thuringiensis (Bt) Cry1F toxin. The level and geographic distribution of Cry1F resistance are not completely known. Neonate S. albicosta from 10 locations between Nebraska and New York state were subjected to dose-response trypsin-activated native Cry1F toxin overlay bioassays. In 2017, the mean estimated lethal concentration causing 50% larval mortality (LC50) ranged from 15.1 to 18.4 µg Cry1F cm-2, and were not significantly different among locations. In 2018, LC50 estimates at Scottsbluff, NE (22.0 µg Cry1F cm-2) and Watertown, NY (21.7 µg Cry1F cm-2) were significantly higher when compared to locations in Michigan (15.8 µg Cry1F cm-2). Significantly lower 14-day larval weight among survivors was correlated with higher Cry1F dose. Results from this study indicate that S. albicosta survivorship on purified Bt Cry1F toxin shows a relatively even distribution across the native and range expansion areas where seasonal field infestations typically occur.
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Affiliation(s)
- Brad S Coates
- USDA-ARS, Corn Insects & Crop Genetics Research Unit, Ames, IA
| | - Craig A Abel
- USDA-ARS, Corn Insects & Crop Genetics Research Unit, Ames, IA
| | - Katharine A Swoboda-Bhattarai
- University of Nebraska-Lincoln, Department of Entomology, West Central Research and Extension Center, North Platte, NE
| | | | - Débora G Montezano
- University of Nebraska-Lincoln, Department of Entomology, West Central Research and Extension Center, North Platte, NE
| | - Sarah N Zukoff
- Kansas State University, Department of Entomology, Southwest Research and Extension Center, Garden City, KS
| | - Yangzhou Wang
- Jilin Academy of Agricultural Sciences, Plant Protection Institute, Changchun, Jilin Province, China
| | - Jeffrey D Bradshaw
- University of Nebraska-Lincoln, Department of Entomology, Panhandle Research and Extension Center, Scottsbluff, NE
| | | | - Elson Shields
- Cornell University, Department of Entomology, Ithaca, NY
| | | | - Thomas E Hunt
- University of Nebraska-Lincoln, Department of Entomology, Haskell Agricultural Laboratory, Concord, NE
| | - Julie A Peterson
- University of Nebraska-Lincoln, Department of Entomology, West Central Research and Extension Center, North Platte, NE
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DAMÚS MELGAREJO ME, PÉREZ ESTIGARRIBIA PE, MASARU IEHISA J, ARRUA JMM, CAZAL MARTÍNEZ CC, ARRUA AA. Contamination of corn grain for human consumption with transgenic sequences in Paraguay. FOOD SCIENCE AND TECHNOLOGY 2020. [DOI: 10.1590/fst.35718] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Tabashnik BE, Carrière Y. Evaluating Cross-resistance Between Vip and Cry Toxins of Bacillus thuringiensis. JOURNAL OF ECONOMIC ENTOMOLOGY 2020; 113:553-561. [PMID: 31821498 DOI: 10.1093/jee/toz308] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/06/2019] [Indexed: 05/27/2023]
Abstract
Crops genetically engineered to produce insecticidal proteins from the bacterium Bacillus thuringiensis (Bt) have revolutionized control of some major pests. Some recently introduced Bt crops make Vip3Aa, a vegetative insecticidal protein (Vip), which reportedly does not share binding sites or structural homology with the crystalline (Cry) proteins of Bt used widely in transgenic crops for more than two decades. Field-evolved resistance to Bt crops with practical consequences for pest control includes 21 cases that collectively reduce the efficacy of nine Cry proteins, but such practical resistance has not been reported yet for any Vip. Here, we review previously published data to evaluate cross-resistance between Vip and Cry toxins. We analyzed 31 cases based on 48 observations, with each case based on one to five observations assessing cross-resistance from pairwise comparisons between 21 resistant strains and 13 related susceptible strains of eight species of lepidopteran pests. Confirming results from previous analyses of smaller data sets, we found weak, statistically significant cross-resistance between Vip3 and Cry1 toxins, with a mean of 1.5-fold cross-resistance in 21 cases (range: 0.30-4.6-fold). Conversely, we did not detect significant positive cross-resistance between Vip3 toxins and Cry2Ab. Distinguishing between weak, significant cross-resistance, and no cross-resistance may be useful for better understanding mechanisms of resistance and effectively managing pest resistance to Bt crops.
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Affiliation(s)
| | - Yves Carrière
- Department of Entomology, University of Arizona, Tucson, AZ
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22
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Yang F, Kerns DL, Head GP, Price PA, Levy R, Niu Y, Huang F. Extended evaluation of Bt protein cross-pollination in seed blend plantings on survival, growth, and development of Helicoverpa zea feeding on refuge ears. PEST MANAGEMENT SCIENCE 2020; 76:1011-1019. [PMID: 31498958 DOI: 10.1002/ps.5611] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2019] [Revised: 09/03/2019] [Accepted: 09/05/2019] [Indexed: 06/10/2023]
Abstract
BACKGROUND A seed blend, also called refuge in a bag (RIB), is used as a strategy to provide refuge for planting pyramided Bt corn in the U.S. Corn Belt. A major concern for the RIB strategy is cross-pollination between Bt and refuge plants, which may reduce susceptible populations of ear-feeding insects like Helicoverpa zea and affect the evolution of resistance. Previous studies showed a 5:95% (Non-Bt: Bt) RIB would be unlikely to provide sufficient refuge populations of H. zea for resistance management. In this study, we extended our research and conducted multiple trials to determine if three RIB plantings with greater refuge sizes (10, 20, and 30% refuge) could provide sufficient H. zea susceptible populations to delay resistance development. RESULTS Experimental results showed that cross-pollination in 10:90%, 20:80%, and 30:70% RIB plantings still significantly reduced larval survival, delayed larval development and decreased the pupal size of H. zea on refuge plants. Regression analysis showed that the percent reduction of neonate-to-adult survivorship, relative to the survivorship on pure non-Bt ears, was significantly negatively correlated with the refuge percentage. CONCLUSION These findings suggest that, approximately a 15% non-Bt refuge plants in RIB plantings could produce a similar number of susceptible adult moths as a 5% structured refuge planting, while an approximately 30% non-Bt refuge plant in RIB plantings could provide a similar number of susceptible moths as a 20% structured refuge planting. Information generated from this study should be useful in refining resistance management strategies for Bt crop technologies. © 2019 Society of Chemical Industry.
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Affiliation(s)
- Fei Yang
- Department of Entomology, Louisiana State University Agricultural Center, Baton Rouge, Louisiana, 70803, USA
- Department of Entomology, Texas A&M University, College Station, Texas, 77843, USA
| | - David L Kerns
- Department of Entomology, Texas A&M University, College Station, Texas, 77843, USA
| | | | | | - Ronnie Levy
- Dean Lee Research Station, Louisiana State University Agricultural Center, Alexandria, Louisiana, 71302, USA
| | - Ying Niu
- Department of Entomology, Louisiana State University Agricultural Center, Baton Rouge, Louisiana, 70803, USA
| | - Fangneng Huang
- Department of Entomology, Louisiana State University Agricultural Center, Baton Rouge, Louisiana, 70803, USA
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23
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Tabashnik BE, Carrière Y. Global Patterns of Resistance to Bt Crops Highlighting Pink Bollworm in the United States, China, and India. JOURNAL OF ECONOMIC ENTOMOLOGY 2019; 112:2513-2523. [PMID: 31254345 DOI: 10.1093/jee/toz173] [Citation(s) in RCA: 51] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/02/2019] [Indexed: 05/29/2023]
Abstract
Crops genetically engineered to produce insecticidal proteins from Bacillus thuringiensis (Bt) have advanced pest control, but their benefits have been reduced by evolution of resistance in pests. The global monitoring data reviewed here reveal 19 cases of practical resistance to Bt crops, which is field-evolved resistance that reduces Bt crop efficacy and has practical consequences for pest control. Each case represents the responses of one pest species in one country to one Bt toxin. The results with pink bollworm (Pectinophora gossypiella) and Bt cotton differ strikingly among the world's three leading cotton-producing nations. In the southwestern United States, farmers delayed resistance by planting non-Bt cotton refuges from 1996 to 2005, then cooperated in a program that used Bt cotton, mass releases of sterile moths, and other tactics to eradicate this pest from the region. In China, farmers reversed low levels of pink bollworm resistance to Bt cotton by planting second-generation hybrid seeds from crosses between Bt and non-Bt cotton. This approach yields a refuge of 25% non-Bt cotton plants randomly interspersed within fields of Bt cotton. Farmers adopted this tactic voluntarily and unknowingly, not to manage resistance, but apparently because of its perceived short-term agronomic and economic benefits. In India, where non-Bt cotton refuges have been scarce and pink bollworm resistance to pyramided Bt cotton producing Cry1Ac and Cry2Ab toxins is widespread, integrated pest management emphasizing shortening of the cotton season, destruction of crop residues, and other tactics is now essential.
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Affiliation(s)
| | - Yves Carrière
- Department of Entomology, University of Arizona, Tucson, AZ
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24
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Caprio MA, Kurtz R, Catchot A, Kerns D, Reisig D, Gore J, Reay-Jones FPF. The Corn-Cotton Agroecosystem in the Mid-Southern United States: What Insecticidal Event Pyramids Should be Used in Each Crop to Extend Vip3A Durability. JOURNAL OF ECONOMIC ENTOMOLOGY 2019; 112:2894-2906. [PMID: 31375824 DOI: 10.1093/jee/toz208] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/26/2019] [Indexed: 06/10/2023]
Abstract
Recent studies suggest that resistance in Helicoverpa zea (Boddie) (Lepidoptera, Noctuidae) to Cry1A(b/c) and Cry2Ab2 toxins from the bacterium Bacillus thuringiensis Berliner (Bacillales: Bacillaceae) has increased and field efficacy is impacted in transgenic corn and cotton expressing these toxins. A third toxin, Vip3A, is available in pyramids expressing two or more Bt toxins in corn hybrids and cotton varieties, but uncertainty exists regarding deployment strategies. During a growing season, H. zea infests corn and cotton, and debate arises over use of Vip3A toxin in corn where H. zea is not an economic pest. We used a three-locus, spatially explicit simulation model to evaluate when using Vip3A in corn might hasten evolution of resistance to Vip3A, with implications in cotton where H. zea is a key pest. When using a conventional refuge in corn and initial resistance allele frequencies of Cry1A and Cry2A were 10%, transforming corn with Vip3A slowed resistance to these toxins and delayed resistance evolution to the three-toxin pyramid as a whole. When Cry resistance allele frequencies exceeded 30%, transforming corn with Vip3A hastened the evolution of resistance to the three-toxin pyramid in cotton. When using a seed blend refuge strategy, resistance was delayed longest when Vip3A was not incorporated into corn and used only in cotton. Simulations of conventional refuges were generally more durable than seed blends, even when 75% of the required refuge was not planted. Extended durability of conventional refuges compared to other models of resistance evolution are discussed as well as causes for unusual survivorship in seed blends.
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Affiliation(s)
- Michael A Caprio
- Department of Biochemistry, Molecular Biology, Entomology and Plant Pathology, Mississippi State University, Mississippi State, MS
| | | | - Angus Catchot
- Department of Biochemistry, Molecular Biology, Entomology and Plant Pathology, Mississippi State University, Mississippi State, MS
| | - David Kerns
- Department of Entomology, Texas A&M University, TAMU, College Station, TX
| | - Dominic Reisig
- Department of Entomology and Plant Pathology, North Carolina State University, Vernon G. James Research and Extension Center, Plymouth, NC
| | - Jeff Gore
- Delta Research & Extension Center, Mississippi State University, Stoneville, MS
| | - Francis P F Reay-Jones
- Department of Plant and Environmental Sciences, Pee Dee Research and Education Center, Clemson University, Florence, SC
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Farhan Y, Smith JL, Schaafsma AW. Susceptibility of Different Instars of Striacosta albicosta (Lepidoptera: Noctuidae) to Vip3A, a Bacillus thuringiensis (Bacillaceae: Bacillales) Protein. JOURNAL OF ECONOMIC ENTOMOLOGY 2019; 112:2335-2344. [PMID: 31114867 DOI: 10.1093/jee/toz118] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/09/2018] [Indexed: 06/09/2023]
Abstract
Striacosta albicosta (Smith) (Lepidoptera: Noctuidae) is an important pest of corn, Zea mays L. in the Great Lakes region, which can be controlled by transgenic corn expressing Vip3A protein from Bacillus thuringiensis. To inform insect resistance management, the susceptibility, survival, and development of first, third, and fifth instar S. albicosta to Vip3A was determined using protein-overlay and corn tissue bioassays. Tissue bioassays were also used to determine the quantity of corn tissues with and without Vip3A-expression consumed by various instars. In diet bioassays, third and fifth instars were significantly less susceptible to Vip3A compared with first instars; however, no significant difference was observed in susceptibility of older instars. In tissue bioassays, survival was lowest for larvae fed Vip3A-expressing tissues, ranging from 0 to 21%, however, developmental measures of larvae fed Vip3A-expressing tissues did not differ from those fed artificial diet or tissues of other Bt events. Consumption of Vip3A × Cry1Ab tissues did not differ from that of Cry1Ab for each instar. Estimated Vip3A exposure of first instars ranged from 3 to 57 times higher than the concentration required for 99% mortality (LC99) based on the product of the reported Vip3A expression in transgenic corn tissues and the consumption observed in tissue bioassays; however, the estimated exposure of third and fifth instars to Vip3A was lower than their respective LC99. These findings suggest that first instar S. albicosta maybe exposed to a high dose of Vip3A under field conditions; however, Vip3A-expression in corn may not be high dose against older instars, increasing the risk of resistance development.
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Affiliation(s)
| | - Jocelyn L Smith
- Department of Plant Agriculture, University of Guelph Ridgetown Campus, Ridgetown, Canada
| | - Arthur W Schaafsma
- Department of Plant Agriculture, University of Guelph Ridgetown Campus, Ridgetown, Canada
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Bilbo TR, Reay-Jones FPF, Reisig DD, Greene JK, Turnbull MW. Development, survival, and feeding behavior of Helicoverpa zea (Lepidoptera: Noctuidae) relative to Bt protein concentrations in corn ear tissues. PLoS One 2019; 14:e0221343. [PMID: 31425563 PMCID: PMC6699733 DOI: 10.1371/journal.pone.0221343] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2019] [Accepted: 08/05/2019] [Indexed: 12/02/2022] Open
Abstract
The corn earworm, Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae), preferentially oviposits and feeds on ears of corn (Zea mays L.) and can be managed using transgenic hybrids that produce insecticidal proteins from the bacterium Bacillus thuringiensis (Bt). Concentrations of Bt proteins can vary spatially and temporally in plant tissues, creating a heterogeneous environment that can increase the risk of resistance development. We planted small-plot trials of nine Bt and non-Bt corn hybrids in South Carolina in 2016 and 2017 and investigated the development, survival, feeding injury, and feeding behavior in corn ear tissues. ELISA was used to quantify the concentrations of Cry1F and Cry2Ab2 in young silk, old silk, maternal tip tissue, kernels, and husk. Cry1F and Cry2Ab2 significantly varied with silk age and both proteins were generally highest in the silk and tip tissue. Hybrids with pyramided proteins significantly reduced feeding injury to the silk, tip, and kernel ear tissues, which was less apparent with single Bt protein hybrids. The pyramided hybrid expressing Vip3A incurred no injury to either the ear tip or kernels, and only eight 1st instar larvae were collected in the silk of 520 sampled ears. Age of larvae significantly varied among ear tissues but not between hybrids. Depending on hybrid family, mean larval instar in the silk, tip, and kernels was 1st or 2nd, 3rd, and 5th, respectively. Instar-specific feeding penetrance into corn ears increased with age but did not differ between hybrids. We characterized the instar- and tissue-specific feeding behavior of H. zea larvae but did not detect differences in feeding behavior between Bt and non-Bt hybrids. Implications for resistance management strategies such as seed mixtures are discussed.
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Affiliation(s)
- Tom R. Bilbo
- Clemson University, Department of Plant and Environmental Sciences, Pee Dee Research and Education Center, Florence, South Carolina, United States of America
| | - Francis P. F. Reay-Jones
- Clemson University, Department of Plant and Environmental Sciences, Pee Dee Research and Education Center, Florence, South Carolina, United States of America
- * E-mail:
| | - Dominic D. Reisig
- North Carolina State University, Department of Entomology and Plant Pathology, Vernon G. James Research and Extension Center, Plymouth, North Carolina, United States of America
| | - Jeremy K. Greene
- Clemson University, Department of Plant and Environmental Sciences, Edisto Research and Education Center, Blackville, South Carolina, United States of America
| | - Matthew W. Turnbull
- Clemson University, Department of Plant and Environmental Sciences, Department of Biological Sciences, Clemson, South Carolina, United States of America
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Bilbo TR, Reay-Jones FPF, Reisig DD, Greene JK. Susceptibility of Corn Earworm (Lepidoptera: Noctuidae) to Cry1A.105 and Cry2Ab2 in North and South Carolina. JOURNAL OF ECONOMIC ENTOMOLOGY 2019; 112:1845-1857. [PMID: 30924858 DOI: 10.1093/jee/toz062] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/2019] [Indexed: 06/09/2023]
Abstract
The corn earworm, Helicoverpa zea (Boddie), is managed in corn and cotton in the United States primarily using transgenic cultivars that produce insecticidal proteins from the bacterium Bacillus thuringiensis (Bt). However, increasing reports of resistance to one or more Bt proteins threaten the continued efficacy of Bt traits. To better understand the development of resistance of H. zea to Bt corn and cotton in the southeastern United States, we monitored for resistance to Cry1A.105 and Cry2Ab2 among 22 field populations of H. zea collected in non-Bt and Bt corn expressing Cry1A.105 + Cry2Ab2 during 2017 and 2018. Colonies were established in the laboratory and progeny were screened in diet-overlay bioassays to purified Cry1A.105 and Cry2Ab2 proteins. Compared with two susceptible laboratory colonies, all 14 field colonies tested with Cry1A.105 were highly resistant, with resistance ratios (RRs) ranging from 13.5 to >4,000. For Cry2Ab2, 19 colonies were tested and RRs ranged from 0.26 to 33.7. Field populations were significantly more susceptible to Cry2Ab2 than Cry1A.105. We documented variability in F0 and F1 pupal weight and developmental rates of natural populations of H. zea, but observed no significant correlation with susceptibility to either Cry1A.105 or Cry2Ab2. Our results expand on the recent reports of H. zea resistance to Cry1A and Cry2A proteins and will aid in the design and deployment of future pyramided crops in the United States.
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Affiliation(s)
- Tom R Bilbo
- Department of Plant and Environmental Sciences, Pee Dee Research and Education Center, Clemson University, Florence, SC
| | - Francis P F Reay-Jones
- Department of Plant and Environmental Sciences, Pee Dee Research and Education Center, Clemson University, Florence, SC
| | - Dominic D Reisig
- Department of Entomology and Plant Pathology, North Carolina State University, the Vernon G. James Research and Extension Center, Plymouth, NC
| | - Jeremy K Greene
- Department of Plant and Environmental Sciences, Edisto Research and Education Center, Clemson University, Blackville, SC
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Niu Y, Guo J, Head GP, Price PA, Huang F. Phenotypic performance of nine genotypes of Cry1A.105/Cry2Ab2 dual-gene resistant fall armyworm on non-Bt and MON 89034 maize. PEST MANAGEMENT SCIENCE 2019; 75:2124-2132. [PMID: 30632285 DOI: 10.1002/ps.5331] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/19/2018] [Revised: 01/08/2019] [Accepted: 01/09/2019] [Indexed: 06/09/2023]
Abstract
BACKGROUND The fall armyworm, Spodoptera frugiperda (J.E. Smith), is the first target pest that has developed resistance to Bt crops across several countries. Leaf tissue and whole plant assays were employed to determine the survival, development, progeny production, and net reproductive rate of all nine possible genotypes of Cry1A.105/Cry2Ab2-dual gene resistant S. frugiperda on non-Bt and MON 89034 maize expressing the Cry1A.105/Cry2Ab2 proteins. RESULTS The homozygous resistant genotype was highly resistant to Bt plants. Genotypes possessing only Cry2Ab2 resistance alleles (RAs) or two Cry1A.105 RAs only were susceptible to MON 89034 with a functional dominance level (DML ) of 0.0-0.07 on MON 89034 plants. In contrast, genotypes containing two Cry1A.105 plus one Cry2Ab2 RA performed well on Bt plants, with a DML of 0.11-0.78. Significant numbers of survivors on Bt plants were also observed for genotypes containing a single Cry1A.105 RA, or a Cry1A.105 plus one or two Cry2Ab2 RAs, with a DML of 0.0-0.47. CONCLUSIONS The fitness of individual resistant genes on pyramided Bt plants varied in the dual-gene resistance system. Genotypes containing more Cry1A.105 RAs performed better than those possessing more Cry2Ab2 RAs. The functional dominance level of an individual resistant gene in this system is related to the DML level in its corresponding single-gene system. Data generated from this study should fill gaps in understanding dual-/multiple-gene Bt resistance, as well as providing useful information for refining resistance modeling, improving resistance risk assessment, and developing management strategies for the sustainable use of pyramided Bt maize technology. © 2019 Society of Chemical Industry.
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Affiliation(s)
- Ying Niu
- Department of Entomology, Louisiana State University Agricultural Center, Baton Rouge, LA, USA
| | - Jianguo Guo
- Department of Entomology, Louisiana State University Agricultural Center, Baton Rouge, LA, USA
- Institute of Plant Protection, Gansu Academy of Agricultural Sciences, Lanzhou, China
| | | | | | - Fangneng Huang
- Department of Entomology, Louisiana State University Agricultural Center, Baton Rouge, LA, USA
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Kaur G, Guo J, Brown S, Head GP, Price PA, Paula-Moraes S, Ni X, Dimase M, Huang F. Field-evolved resistance of Helicoverpa zea (Boddie) to transgenic maize expressing pyramided Cry1A.105/Cry2Ab2 proteins in northeast Louisiana, the United States. J Invertebr Pathol 2019; 163:11-20. [DOI: 10.1016/j.jip.2019.02.007] [Citation(s) in RCA: 58] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2018] [Revised: 12/13/2018] [Accepted: 02/22/2019] [Indexed: 11/28/2022]
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Yang F, González JCS, Williams J, Cook DC, Gilreath RT, Kerns ADL. Occurrence and Ear Damage of Helicoverpa zea on Transgenic Bacillus thuringiensis Maize in the Field in Texas, U.S. and Its Susceptibility to Vip3A Protein. Toxins (Basel) 2019; 11:toxins11020102. [PMID: 30744120 PMCID: PMC6416581 DOI: 10.3390/toxins11020102] [Citation(s) in RCA: 52] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2018] [Revised: 02/05/2019] [Accepted: 02/07/2019] [Indexed: 01/04/2023] Open
Abstract
The corn earworm, Helicoverpa zea (Boddie), is a major pest of Bacillus thuringiensis (Bt) maize and cotton in the U.S. Reduced efficacy of Bt plants expressing Cry1 and Cry2 against H. zea has been reported in some areas of the U.S. In this study, we evaluated the occurrence and ear damage of H. zea on transgenic Bt maize expressing Cry proteins or a combination of Vip3A and Cry proteins in the field in Texas in 2018. We found that the occurrence of H. zea larvae and the viable kernel damage area on the ear were not different between non-Bt maize and Bt maize expressing Cry1A.105+Cry2Ab2 and Cry1Ab+Cry1F proteins. A total of 67.5% of the pyramided Bt maize expressing Cry1Ab+Cry1F+Vip3A was damaged by 2nd–4th instar larvae of H. zea. Diet bioassays showed that the resistance ratio against Vip3Aa51 for H. zea obtained from Cry1Ab+Cry1F+Vip3A maize was 20.4 compared to a field population collected from Cry1F+Cry1A.105+Cry2Ab2 maize. Leaf tissue bioassays showed that 7-day survivorship on WideStrike3 (Cry1F+Cry1Ac+Vip3A) cotton leaves was significantly higher for the H. zea population collected from Cry1Ab+Cry1F+Vip3A maize than for a Bt-susceptible laboratory population. The results generated from this study suggest that H. zea has evolved practical resistance to Cry1 and Cry2 proteins. Therefore, it is crucial to ensure the sustainable use of the Vip3A technology in Bt maize and cotton.
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Affiliation(s)
- Fei Yang
- Department of Entomology, Texas A&M University, College Station, TX 77843-2475, USA.
| | | | | | - Donald C Cook
- Delta Research and Extension Center, Mississippi State University, Stoneville, MS 38776, USA.
| | - Ryan T Gilreath
- Department of Entomology, Texas A&M University, College Station, TX 77843-2475, USA.
| | - And David L Kerns
- Department of Entomology, Texas A&M University, College Station, TX 77843-2475, USA.
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Zhou L, Alphey N, Walker AS, Travers LM, Hasan F, Morrison NI, Bonsall MB, Raymond B. Combining the high-dose/refuge strategy and self-limiting transgenic insects in resistance management-A test in experimental mesocosms. Evol Appl 2018; 11:727-738. [PMID: 29875814 PMCID: PMC5979637 DOI: 10.1111/eva.12573] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2017] [Accepted: 10/23/2017] [Indexed: 12/21/2022] Open
Abstract
The high-dose/refuge strategy has been the primary approach for resistance management in transgenic crops engineered with Bacillus thuringiensis toxins. However, there are continuing pressures from growers to reduce the size of Bt toxin-free refugia, which typically suffer higher damage from pests. One complementary approach is to release male transgenic insects with a female-specific self-limiting gene. This technology can reduce population sizes and slow the evolution of resistance by introgressing susceptible genes through males. Theory predicts that it could be used to facilitate smaller refugia or reverse the evolution of resistance. In this study, we used experimental evolution with caged insect populations to investigate the compatibility of the self-limiting system and the high-dose/refuge strategy in mitigating the evolution of resistance in diamondback moth, Plutella xylostella. The benefits of the self-limiting system were clearer at smaller refuge size, particularly when refugia were inadequate to prevent the evolution of resistance. We found that transgenic males in caged mesocosms could suppress population size and delay resistance development with 10% refugia and 4%-15% initial resistance allele frequency. Fitness costs in hemizygous transgenic insects are particularly important for introgressing susceptible alleles into target populations. Fitness costs of the self-limiting gene in this study (P. xylostella OX4139 line L) were incompletely dominant, and reduced fecundity and male mating competitiveness. The experimental evolution approach used here illustrates some of the benefits and pitfalls of combining mass release of self-limiting insects and the high-dose/refuge strategy, but does indicate that they can be complementary.
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Affiliation(s)
- Liqin Zhou
- Imperial College LondonLondonUK
- University of ExeterExeterUK
| | - Nina Alphey
- Imperial College LondonLondonUK
- Department of ZoologyUniversity of OxfordOxfordUK
- The Pirbright InstituteSurreyUK
| | | | | | | | | | - Michael B. Bonsall
- Imperial College LondonLondonUK
- Department of ZoologyUniversity of OxfordOxfordUK
| | - Ben Raymond
- Imperial College LondonLondonUK
- University of ExeterExeterUK
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Farhan Y, Smith JL, Schaafsma AW. Baseline Susceptibility of Striacosta albicosta (Lepidoptera: Noctuidae) in Ontario, Canada to Vip3A Bacillus thuringiensis Protein. JOURNAL OF ECONOMIC ENTOMOLOGY 2018; 111:65-71. [PMID: 29186433 DOI: 10.1093/jee/tox296] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/11/2017] [Indexed: 06/07/2023]
Abstract
Striacosta albicosta (Smith; Lepidoptera: Noctuidae) is a pest of corn (Zea mays L.), which has recently expanded its range into Ontario, Canada. Genetically modified corn expressing Vip3A insecticidal protein from Bacillus thuringiensis is a biotechnological option for the control of S. albicosta. To support an insect resistance management program, we conducted a study of baseline susceptibility of 10-field collected S. albicosta populations in Ontario, Canada to Vip3A before widespread commercial adoption. Neonates were exposed to artificial diet overlaid with Vip3A. The LC50 ranged from 22.7 to 53.5 ng Vip3A cm-2. The EC50 ranged from 11.4 to 30.2 ng Vip3A cm-2. There was low inter-population variation in susceptibility to Vip3A, which we believe represents the natural geographical variation in response and not variation caused by previous exposure to selection pressure of the Vip3A protein.
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Affiliation(s)
- Yasmine Farhan
- Department of Plant Agriculture, Ridgetown Campus, University of Guelph, Ridgetown, ON, Canada
| | - Jocelyn L Smith
- Department of Plant Agriculture, Ridgetown Campus, University of Guelph, Ridgetown, ON, Canada
| | - Arthur W Schaafsma
- Department of Plant Agriculture, Ridgetown Campus, University of Guelph, Ridgetown, ON, Canada
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Onstad DW, Crespo ALB, Pan Z, Crain PR, Thompson SD, Pilcher CD, Sethi A. Blended Refuge and Insect Resistance Management for Insecticidal Corn. ENVIRONMENTAL ENTOMOLOGY 2018; 47:210-219. [PMID: 29220481 PMCID: PMC5850660 DOI: 10.1093/ee/nvx172] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 06/09/2017] [Indexed: 06/07/2023]
Abstract
In this review, we evaluate the intentional mixing or blending of insecticidal seed with refuge seed for managing resistance by insects to insecticidal corn (Zea mays). We first describe the pest biology and farming practices that will contribute to weighing trade-offs between using block refuges and blended refuges. Case studies are presented to demonstrate how the trade-offs will differ in different systems. We compare biological aspects of several abstract models to guide the reader through the history of modeling, which has played a key role in the promotion or denigration of blending in various scientific debates about insect resistance management for insecticidal crops. We conclude that the use of blended refuge should be considered on a case-by-case basis after evaluation of insect biology, environment, and farmer behavior. For Diabrotica virgifera virgifera, Ostrinia nubilalis, and Helicoverpa zea in the United States, blended refuge provides similar, if not longer, delays in the evolution of resistance compared to separate block refuges.
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Svobodová Z, Burkness EC, Skoková Habuštová O, Hutchison WD. Predator Preference for Bt-Fed Spodoptera frugiperda (Lepidoptera: Noctuidae) Prey: Implications for Insect Resistance Management in Bt Maize Seed Blends. JOURNAL OF ECONOMIC ENTOMOLOGY 2017; 110:1317-1325. [PMID: 28369505 DOI: 10.1093/jee/tox098] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/19/2017] [Indexed: 06/07/2023]
Abstract
Understanding indirect, trophic-level effects of genetically engineered plants, expressing insecticidal proteins derived from the bacterium, Bacillus thuringiensis (Bt), is essential to the ecological risk assessment process. In this study, we examine potential indirect, trophic-level effects of Bt-sensitive prey using the predator, Harmonia axyridis (Pallas), feeding upon Spodoptera frugiperda (J.E. Smith) larvae, which had delayed development (lower body mass) following ingestion of Cry1Ab maize leaves. We found no adverse effects on development and survival when H. axyridis larvae were fed S. frugiperda larvae that had fed on Cry1Ab maize tissue. Presence of Cry1Ab in H. axyridis decreased considerably after switching to another diet within 48 h. In a no-choice assay, H. axyridis larvae consumed more Bt-fed S. frugiperda than non-Bt-fed larvae. Preference for S. frugiperda feeding on Bt maize was confirmed in subsequent choice assays with H. axyridis predation on Bt-fed, 1-5-d-old S. frugiperda larvae. We suggest that H. axyridis preferred prey, not based on whether it had fed on Bt or non-Bt maize, but rather on larval mass, and they compensated for the nutritional deficiency of lighter larvae through increased consumption. Pest larvae with variable levels of resistance developing on Bt diet are often stunted versus sensitive larvae developing on non-Bt diet. It is possible that such larvae may be preferentially removed from local field populations. These results may have implications for insect resistance management and may be played out under field conditions where seed blends of Bt and non-Bt hybrids are planted.
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Affiliation(s)
- Z Svobodová
- Institute of Entomology, Biology Centre CAS, Branišovská 31, České Budějovice 370 05, Czech Republic ( ; )
- Faculty of Science, University of South Bohemia, Branišovská 31, České Budějovice 370 05, Czech Republic
| | - E C Burkness
- Department of Entomology, University of Minnesota, 1980 Folwell Ave., St. Paul, MN 55108-6125 ( ; )
- Corresponding author, e-mail:
| | - O Skoková Habuštová
- Institute of Entomology, Biology Centre CAS, Branišovská 31, Ceské Budejovice 370 05, Czech Republic (; )
| | - W D Hutchison
- Department of Entomology, University of Minnesota, 1980 Folwell Ave., St. Paul, MN 55108-6125 (; )
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Dively GP, Venugopal PD, Finkenbinder C. Field-Evolved Resistance in Corn Earworm to Cry Proteins Expressed by Transgenic Sweet Corn. PLoS One 2016; 11:e0169115. [PMID: 28036388 PMCID: PMC5201267 DOI: 10.1371/journal.pone.0169115] [Citation(s) in RCA: 106] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2016] [Accepted: 12/11/2016] [Indexed: 12/22/2022] Open
Abstract
Background Transgenic 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 Findings We 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/Significance After 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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Affiliation(s)
- Galen P. Dively
- Department of Entomology, University of Maryland, College Park, Maryland, United States of America
| | - P. Dilip Venugopal
- Department of Entomology, University of Maryland, College Park, Maryland, United States of America
- American Association for the Advancement of Science - Science and Technology Policy Fellowship Program, Transportation and Climate Division, Office of Transportation & Air Quality, United States Environmental Protection Agency, District of Columbia, United States of America
- * E-mail:
| | - Chad Finkenbinder
- Benzon Research Inc., Carlisle, Pennsylvania, United States of America
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Garcia AG, Ferreira CP, Cônsoli FL, Godoy WA. Predicting evolution of insect resistance to transgenic crops in within-field refuge configurations, based on larval movement. ECOLOGICAL COMPLEXITY 2016. [DOI: 10.1016/j.ecocom.2016.07.006] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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Reay-Jones FPF, Bessin RT, Brewer MJ, Buntin DG, Catchot AL, Cook DR, Flanders KL, Kerns DL, Porter RP, Reisig DD, Stewart SD, Rice ME. Impact of Lepidoptera (Crambidae, Noctuidae, and Pyralidae) Pests on Corn Containing Pyramided Bt Traits and a Blended Refuge in the Southern United States. JOURNAL OF ECONOMIC ENTOMOLOGY 2016; 109:1859-1871. [PMID: 27329627 DOI: 10.1093/jee/tow109] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/02/2016] [Accepted: 04/27/2016] [Indexed: 06/06/2023]
Abstract
Blended refuge for transgenic plants expressing Bacillus thuringiensis (Bt) toxins has been approved in the northern United States as a resistance management strategy alternative to a structured refuge. A three-year study (2012-2014) was conducted with 54 trials across nine states in the southern United States to evaluate plant injury from lepidopteran pests of corn and yield in a corn hybrid expressing Cry1F × Cry1Ab × Vip3Aa20 (Pioneer Brand Optimum Leptra) planted as a pure stand and in refuge blends of 5, 10, and 20% in both early and late plantings. Injury by corn earworm, Helicoverpa zea Boddie (Lepidoptera: Noctuidae), and fall armyworm, Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae), was generally proportional to the percentage of non-Bt corn within each refuge blend. Across locations, ear injury in plots with 100% Cry1F × Cry1Ab × Vip3Aa20 (Optimum Leptra) corn ranged from no injury to a maximum of 0.42 cm(2) per ear in Mississippi in 2013. Leaf injury ratings in 100% non-Bt plots in early and late planted trials in 2014 were 86- and 70-fold greater than in 100% Cry1F × Cry1Ab × Vip3Aa20 (Optimum Leptra) plots. Plants in plots with blended refuges had significantly greater leaf injury in 2012 (5, 10, and 20% refuge blends), in the early-planted corn in 2013 (10 and 20% only), and in both early- and late-planted corn in 2014 (20% only) as compared with leaf injury in a pure stand of Cry1F × Cry1Ab × Vip3Aa20 (Optimum Leptra) seen during these years. Corn ears in plots with blended refuges also had significantly greater area of kernels injured in 2012 (5, 10, and 20%), in early- and late-planted corn in 2013 (5, 10, and 20%), and in early (10 and 20% only)- and late-planted corn (5, 10, and 20%) in 2014 as compared with ear injury in a pure stand of Cry1F × Cry1Ab × Vip3Aa20 (Optimum Leptra) seen during these years. Infestations of southwestern corn borer, Diatraea grandiosella Dyar (Lepidoptera: Crambidae), were also significantly reduced by Cry1F × Cry1Ab × Vip3Aa20 (Optimum Leptra). Despite these differences in injury, yield averaged across locations varied among refuge blends only in the late-planted trials in 2013, with greater yields in the 0% refuge blend than in the 20% blend; however, when examining yield separately by location, only two of nine locations had higher yields in the 100% Bt plots than in any of the blended refuge plots. As a complement to studying the contribution of blended refuge to delaying resistance, quantifying injury and yield in a range of refuge blends is a necessary step to provide management information on the range of lepidopteran pests that occur in the southern United States.
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Affiliation(s)
- F P F Reay-Jones
- Department of Agricultural and Environmental Sciences, Pee Dee Research and Education Center, Clemson University, 2200 Pocket Rd., Florence, SC 29506-9727
| | - R T Bessin
- Department of Entomology, University of Kentucky, S-225 Ag North, Lexington, KY 40546
| | - M J Brewer
- Texas A&M AgriLife Research & Extension Center, 10345 State Hwy 44, Corpus Christi, TX 78406
| | - D G Buntin
- Department of Entomology, UGA-Griffin Campus, 1109 Experiment Street, Griffin, GA 30223
| | - A L Catchot
- Department of Entomology & Plant Pathology, Mississippi State University, Mississippi State, MS 39762
| | - D R Cook
- Delta Research & Extension Center, Mississippi State University, P.O. Box 197, Stoneville, MS 38776
| | | | - D L Kerns
- LSU AgCenter, Macon Ridge Station, 212A Macon Ridge Rd., Winnsboro, LA 71295
| | - R P Porter
- Texas AgriLife Research & Extension Center, Lubbock, TX 79403
| | - D D Reisig
- Department of Entomology, North Carolina State University, Vernon G. James Research and Extension Center, Plymouth, NC 27962
| | - S D Stewart
- West Tennessee Research and Education Center, 605 Airways Blvd., Jackson, TN 38301
| | - M E Rice
- DuPont Pioneer, P. O. Box 1150, Johnston, IA 50131 , and
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Can Pyramids and Seed Mixtures Delay Resistance to Bt Crops? Trends Biotechnol 2016; 34:291-302. [DOI: 10.1016/j.tibtech.2015.12.011] [Citation(s) in RCA: 147] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2015] [Revised: 12/15/2015] [Accepted: 12/16/2015] [Indexed: 01/29/2023]
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Pan Z, Onstad D, Crain P, Crespo A, Hutchison W, Buntin D, Porter P, Catchot A, Cook D, Pilcher C, Flexner L, Higgins L. Evolution of Resistance by Helicoverpa zea (Lepidoptera: Noctuidae) Infesting Insecticidal Crops in the Southern United States. JOURNAL OF ECONOMIC ENTOMOLOGY 2016; 109:821-831. [PMID: 26637533 PMCID: PMC4821455 DOI: 10.1093/jee/tov340] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/27/2015] [Accepted: 11/04/2015] [Indexed: 06/05/2023]
Abstract
We created a deterministic, frequency-based model of the evolution of resistance by corn earworm, Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae), to insecticidal traits expressed in crops planted in the heterogeneous landscapes of the southern United States. The model accounts for four generations of selection by insecticidal traits each year. We used the model results to investigate the influence of three factors on insect resistance management (IRM): 1) how does adding a third insecticidal trait to both corn and cotton affect durability of the products, 2) how does unstructured corn refuge influence IRM, and 3) how do block refuges (50% compliance) and blended refuges compare with regard to IRM? When Bt cotton expresses the same number of insecticidal traits, Bt corn with three insecticidal traits provides longer durability than Bt corn with two pyramided traits. Blended refuge provides similar durability for corn products compared with the same level of required block refuge when the rate of refuge compliance by farmers is 50%. Results for Mississippi and Texas are similar, but durabilities for corn traits are surprisingly lower in Georgia, where unstructured corn refuge is the highest of the three states, but refuge for Bt cotton is the lowest of the three states. Thus, unstructured corn refuge can be valuable for IRM but its influence is determined by selection for resistance by Bt cotton.
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Affiliation(s)
- Zaiqi Pan
- DuPont Pioneer, Wilmington, DE 19803 (; ; ; )
| | | | | | | | - William Hutchison
- Department of Entomology, University of Minnesota, St. Paul, MN 55108
| | - David Buntin
- Department of Entomology, University of Georgia, Griffin, GA 30223
| | - Pat Porter
- Department of Entomology, Texas A & M AgriLife Extension, Lubbock, TX 79403
| | - Angus Catchot
- Department of Entomology and Plant Pathology, Mississippi State University, Mississippi State, MS 39762 , and
| | - Don Cook
- Delta Research and Extension Center, Mississippi State University, Stoneville, MS 38756
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Crespo ALB, Alves AP, Wang Y, Hong B, Flexner JL, Catchot A, Buntin D, Cook D. Survival of Corn Earworm (Lepidoptera: Noctuidae) on Bt Maize and Cross-Pollinated Refuge Ears From Seed Blends. JOURNAL OF ECONOMIC ENTOMOLOGY 2016; 109:288-298. [PMID: 26357846 DOI: 10.1093/jee/tov272] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/25/2015] [Accepted: 08/24/2015] [Indexed: 06/05/2023]
Abstract
Refuge is mandated in the United States where genetically modified maize (Zea mays L.) expressing insecticidal proteins derived from Bacillus thuringiensis Berliner (Bt) are cultivated. Currently, refuge is deployed in different ways including blocks, field strips, or seed blends containing Bt and non-Bt maize. Seed blends provide practical advantages for refuge implementation. However, concerns related to the movement of insect larvae, potential differential survival of heterozygous resistant larvae, reduction in insect production, and cross-pollination of ears resulting in sublethal selection, have delayed seed blend use for Lepidoptera in the southern United States, where maize plantings are used as refuge for Helicoverpa zea (Boddie). In this study, we evaluated the relative survival of H. zea in Bt events and in seed blends compared with pure stand refuge and the relative survival of H. zea on the individual components of the pyramid 1507xMON810xMIR162. The results showed variation on the production of H. zea in refuge plants from seed blends compared with pure stand refuge plants. The relative survival of H. zea on the events 1507, MON810, MIR162, and 1507xMON810xMIR162 ranked similarly across the three locations tested. These results can be used in computer simulation modeling efforts to evaluate the feasibility of seed blends as a refuge deployment strategy with the pyramid 1507xMON810xMIR162. Because the reduction on survival of H. zea due to blending was variable, a sensitivity analysis that includes all possible scenarios of reduction in survival should be considered.
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Affiliation(s)
| | | | - Yiwei Wang
- DuPont Pioneer, Johnston, IA 50131, USA (; ; ; )
| | - Bonnie Hong
- DuPont Pioneer, Johnston, IA 50131, USA (; ; ; )
| | | | - Angus Catchot
- Department of Entomology and Plant Pathology, Mississippi State University, Mississippi State, MS 39762-9775, USA
| | - David Buntin
- Department of Entomology, University of Georgia, Plains, GA 30223, USA , and
| | - Donald Cook
- Delta Research and Extension Center, Mississippi State University, Stoneville, MS 38776, USA
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Caprio MA, Martinez JC, Porter PA, Bynum E. The Impact of Inter-Kernel Movement in the Evolution of Resistance to Dual-Toxin Bt-Corn Varieties in Helicoverpa zea (Lepidoptera: Noctuidae). JOURNAL OF ECONOMIC ENTOMOLOGY 2016; 109:307-319. [PMID: 26527792 DOI: 10.1093/jee/tov295] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/15/2015] [Accepted: 09/11/2015] [Indexed: 06/05/2023]
Abstract
Seeds or kernels on hybrid plants are primarily F(2) tissue and will segregate for heterozygous alleles present in the parental F(1) hybrids. In the case of plants expressing Bt-toxins, the F(2) tissue in the kernels will express toxins as they would segregate in any F(2) tissue. In the case of plants expressing two unlinked toxins, the kernels on a Bt plant fertilized by another Bt plant would express anywhere from 0 to 2 toxins. Larvae of corn earworm [Helicoverpa zea (Boddie)] feed on a number of kernels during development and would therefore be exposed to local habitats (kernels) that varied in their toxin expression. Three models were developed for plants expressing two Bt-toxins, one where the traits are unlinked, a second where the traits were linked and a third model assuming that maternal traits were expressed in all kernels as well as paternally inherited traits. Results suggest that increasing larval movement rates off of expressing kernels tended to increase durability while increasing movement rates off of nonexpressing kernels always decreased durability. An ideal block refuge (no pollen flow between blocks and refuges) was more durable than a seed blend because the refuge expressed no toxins, while pollen contamination from plants expressing toxins in a seed blend reduced durability. A linked-trait model in an ideal refuge model predicted the longest durability. The results suggest that using a seed-blend strategy for a kernel feeding insect on a hybrid crop could dramatically reduce durability through the loss of refuge due to extensive cross-pollination.
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Affiliation(s)
- Michael A Caprio
- Department of Biochemistry, Molecular Biology, Entomology and Plant Pathology, Mississippi State University, Mississippi State, MS 39762 (; ; ),
| | - Jeannette C Martinez
- Department of Biochemistry, Molecular Biology, Entomology and Plant Pathology, Mississippi State University, Mississippi State, MS 39762 (; ; )
| | - Patrick A Porter
- Department of Entomology, Texas A & M University, College Station, TX, 77843
| | - Ed Bynum
- Department of Entomology, Texas A & M University, College Station, TX, 77843
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Burkness EC, Cira TM, Moser SE, Hutchison WD. Bt Maize Seed Mixtures for Helicoverpa zea (Lepidoptera: Noctuidae): Larval Movement, Development, and Survival on Non-transgenic Maize. JOURNAL OF ECONOMIC ENTOMOLOGY 2015; 108:2761-2769. [PMID: 26318006 DOI: 10.1093/jee/tov253] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2015] [Accepted: 08/06/2015] [Indexed: 06/04/2023]
Abstract
In 2012 and 2013, field trials were conducted near Rosemount, MN, to assess the movement and development of Helicoverpa zea (Boddie) larvae on non-Bt refuge corn plants within a seed mixture of non-Bt and Bt corn. The Bt corn hybrid expressed three Bt toxins-Cry1Ab, Cry1F, and Vip3A. As the use of seed mixtures for insect resistance management (IRM) continues to be implemented, it is necessary to further characterize how this IRM approach impacts resistance development in ear-feeding Lepidopteran pests. The potential for Bt pollen movement and cross pollination of the non-Bt ears in a seed mixture may lead to Bt toxin exposure to larvae developing on those refuge ears. Larval movement and development by H. zea, feeding on non-Bt refuge plants adjacent to either transgenic Bt or non-Bt plants, were measured to investigate the potential for unintended Bt exposure. Non-Bt plants were infested with H. zea eggs and subplots were destructively sampled twice per week within each treatment to assess larval development, location, and kernel injury. Results indicate that H. zea larval movement between plants is relatively low, ranging from 2-16% of larvae, and occurs mainly after reaching the second instar. Refuge plants in seed mixtures did not produce equivalent numbers of H. zea larvae, kernel injury, and larval development differed as compared with a pure stand of non-Bt plants. This suggests that there may be costs to larvae developing on refuge plants within seed mixtures and additional studies are warranted to define potential impacts.
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Affiliation(s)
- Eric C Burkness
- Department of Entomology, University of Minnesota, 1980 Folwell Avenue, St. Paul, MN 55108-6125.
| | - T M Cira
- Department of Entomology, University of Minnesota, 1980 Folwell Avenue, St. Paul, MN 55108-6125
| | - S E Moser
- DuPont Pioneer, 7250 NW 62nd Ave., Johnston, IA 50131
| | - W D Hutchison
- Department of Entomology, University of Minnesota, 1980 Folwell Avenue, St. Paul, MN 55108-6125
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A seed mixture increases dominance of resistance to Bt cotton in Helicoverpa zea. Sci Rep 2015; 5:9807. [PMID: 25950459 PMCID: PMC4423431 DOI: 10.1038/srep09807] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2014] [Accepted: 03/19/2015] [Indexed: 12/25/2022] Open
Abstract
Widely grown transgenic crops producing insecticidal proteins from Bacillus thuringiensis (Bt) can benefit agriculture, but adaptation by pests threatens their continued success. Refuges of host plants that do not make Bt toxins can promote survival of susceptible insects and delay evolution of resistance, particularly if resistance is inherited as a recessive trait. However, data have been lacking to compare the dominance of resistance when Bt and non-Bt seeds are planted in random mixtures versus separate blocks. Here we report results from greenhouse experiments with transgenic cotton producing Bt toxin Cry1Ac and the bollworm, Helicoverpa zea, showing that the dominance of resistance was significantly higher in a seed mixture relative to a block of Bt cotton. The proportion of larvae on non-Bt cotton plants in the seed mixture was also significantly higher than expected under the null hypothesis of random distribution. In simulations based on observed survival, resistance evolved 2- to 4.5-fold faster in the seed mixture relative to separate blocks of Bt and non-Bt cotton. These findings support previous modelling results indicating that block refuges may be more effective than seed mixtures for delaying resistance in pests with mobile larvae and inherently low susceptibility to the toxins in Bt crops.
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