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Reay-Jones FPF, Buntin GD, Reisig DD, Bridges WC. Longitudinal trials illustrate interactive effects between declining Bt efficacy against Helicoverpa zea (Lepidoptera: Noctuidae) and planting dates of corn. JOURNAL OF ECONOMIC ENTOMOLOGY 2024:toae160. [PMID: 39041329 DOI: 10.1093/jee/toae160] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/15/2024] [Revised: 06/06/2024] [Accepted: 07/02/2024] [Indexed: 07/24/2024]
Abstract
Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae) has evolved resistance to insecticidal toxins from Bacillus thuringiensis (Bt) Berliner (Bacillales: Bacillaceae) expressed in genetically engineered corn, Zea mays L. This study provides an overview of field trials from Georgia, North Carolina, and South Carolina evaluating Bt and non-Bt corn hybrids from 2009 to 2022 to show changes in susceptibility in H. zea to Bt corn. The reduction in kernel injury relative to a non-Bt hybrid averaged across planting dates generally declined over time for Cry1A.105 + Cry2Ab2 corn. In addition, there was a significant interaction with planting date used as a covariate. The reduction in kernel injury remained above 80% and did not vary with planting date from 2009 to 2014, whereas a significant decline with planting date was found in this reduction from 2015 to 2022. For Cry1Ab + Cry1F corn, the reduction in kernel injury relative to a non-Bt hybrid averaged across planting dates did not vary among years. The reduction in kernel injury significantly declined with planting date from 2012 to 2022. Kernel injury as a proxy for H. zea pressure was greater in late-planted trials in non-Bt corn hybrids. Our study showed that Bt hybrids expressing Cry1A.105 + Cry2Ab2 are now less effective in later planted trials in reducing H. zea injury; however, this was not the case during the earlier years of adoption of corn expressing these 2 toxins when resistance alleles were likely less frequent in H. zea populations. The implications for management of H. zea and for insect resistance management are discussed.
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Affiliation(s)
- Francis P F Reay-Jones
- Department of Plant and Environmental Sciences, Pee Dee Research and Education Center, Clemson University, Florence, SC 29506-9727, USA
| | - G David Buntin
- Department of Entomology, University of Georgia, Griffin, GA 30223, USA
| | - Dominic D Reisig
- Department of Entomology and Plant Pathology, North Carolina State University, The Vernon G. James Research and Extension Center, Plymouth, NC 27962, USA
| | - William C Bridges
- Department of Mathematical Sciences, Clemson University, Clemson, SC, 29634, USA
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Bryant TB, Greene JK, Reisig D, Reay-Jones FPF. Continued decline in sublethal effects of Bt toxins on Helicoverpa zea (Lepidoptera: Noctuidae) in field corn. JOURNAL OF ECONOMIC ENTOMOLOGY 2024:toae152. [PMID: 38984916 DOI: 10.1093/jee/toae152] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/15/2024] [Revised: 06/11/2024] [Accepted: 06/22/2024] [Indexed: 07/11/2024]
Abstract
The majority of field corn, Zea mays L., in the southeastern United States has been genetically engineered to express insecticidal toxins produced by the soil bacterium, Bacillus thuringiensis (Bt). Field corn is the most important mid-season host for corn earworm, Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae), which has developed resistance to all Cry toxins in Bt corn. From 2020 to 2023, corn earworm pupae were collected from early- and late-planted pyramided hybrids expressing Bt toxins and non-Bt near-isolines in North and South Carolina (16 trials). A total of 5,856 pupae were collected across all trials, with 55 and 88% more pupae collected in later-planted trials relative to early plantings in North and South Carolina, respectively. Only 20 pupae were collected from hybrids expressing Cry1F + Cry1Ab + Vip3A20 across all trials. Averaged across trials, Cry1A.105 + Cry2Ab2 hybrids reduced pupal weight by 6 and 9% in North and South Carolina, respectively, relative to the non-Bt near-isoline. Cry1F + Cry1Ab hybrids reduced pupal weight on average by 3 and 8% in North and South Carolina, respectively, relative to the non-Bt near-isoline. The impact of the Bt toxins on pupal weight varied among trials. When combined with data from 2014 to 2019 from previous studies, a significant decline in the percent reduction in pupal weight over time was found in both states and hybrid families. This study demonstrates a continued decline in the sublethal impacts of Bt toxins on corn earworm, emphasizing the importance of insect resistance management practices.
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Affiliation(s)
- Tim B Bryant
- Department of Plant and Environmental Sciences, Pee Dee Research and Education Center, Clemson University, Florence, SC, USA
| | - Jeremy K Greene
- Department of Plant and Environmental Sciences, Edisto Research and Education Center, Clemson University, Blackville, SC, USA
| | - Dominic Reisig
- Department of Entomology and Plant Pathology, Vernon G. James Research and Extension Center, North Carolina State University, Plymouth, NC, USA
| | - Francis P F Reay-Jones
- Department of Plant and Environmental Sciences, Pee Dee Research and Education Center, Clemson University, Florence, SC, USA
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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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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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De Bortoli CP, Santos RF, Assirati GJ, Sun X, Hietala L, Jurat-Fuentes JL. Exposure to Cry1 Toxins Increases Long Flight Tendency in Susceptible but Not in Cry1F-Resistant Female Spodoptera frugiperda (Lepidoptera: Noctuidae). INSECTS 2023; 15:7. [PMID: 38249013 PMCID: PMC10815942 DOI: 10.3390/insects15010007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/12/2023] [Revised: 12/15/2023] [Accepted: 12/18/2023] [Indexed: 01/23/2024]
Abstract
The fall armyworm (JE Smith) (Spodoptera frugiperda) is a polyphagous pest targeted by selected Cry and Vip3A insecticidal proteins from the bacterium Bacillus thuringiensis (Bt) that are produced in transgenic Bt corn and cotton. Available evidence suggests that sublethal larval exposure to Cry1Ac increases flight activity in adult Spodoptera spp. However, it is not known whether this effect is also observed in survivors from generally lethal exposure to Cry1Ac. Moreover, while multiple cases of field-evolved resistance to Bt proteins have been described in the native range of S. frugiperda, the effect of resistance on flight behavior has not been examined. Long-distance migratory flight capacity of S. frugiperda is of concern given its ongoing global spread and the possibility that migrants may be carrying resistance alleles against pesticides and Bt crops. In this study, we used rotational flight mills to test the effects of generally lethal exposure to Cry1Ac in susceptible and sublethal exposure in Cry1F-resistant S. frugiperda strains. The results detected altered pupal weight after larval feeding on diet containing Cry proteins, which only translated in significantly increased tendency for longer flights in female moths from the susceptible strain. This information has relevant implications when considering current models and assumptions for resistance management of Bt crops.
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Affiliation(s)
- Caroline P. De Bortoli
- Department of Entomology and Plant Pathology, University of Tennessee, Knoxville, TN 37996, USA; (C.P.D.B.); (R.F.S.); (G.J.A.); (L.H.)
| | - Rafael F. Santos
- Department of Entomology and Plant Pathology, University of Tennessee, Knoxville, TN 37996, USA; (C.P.D.B.); (R.F.S.); (G.J.A.); (L.H.)
| | - Giordano J. Assirati
- Department of Entomology and Plant Pathology, University of Tennessee, Knoxville, TN 37996, USA; (C.P.D.B.); (R.F.S.); (G.J.A.); (L.H.)
| | - Xiaocun Sun
- Research Computing Support, Office of Information Technology, University of Tennessee, Knoxville, TN 37996, USA;
| | - Lucas Hietala
- Department of Entomology and Plant Pathology, University of Tennessee, Knoxville, TN 37996, USA; (C.P.D.B.); (R.F.S.); (G.J.A.); (L.H.)
| | - Juan Luis Jurat-Fuentes
- Department of Entomology and Plant Pathology, University of Tennessee, Knoxville, TN 37996, USA; (C.P.D.B.); (R.F.S.); (G.J.A.); (L.H.)
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