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Tay WT, Rane RV, James W, Gordon KHJ, Downes S, Kim J, Kuniata L, Walsh TK. Resistance Bioassays and Allele Characterization Inform Analysis of Spodoptera frugiperda (Lepidoptera: Noctuidae) Introduction Pathways in Asia and Australia. JOURNAL OF ECONOMIC ENTOMOLOGY 2022; 115:1790-1805. [PMID: 36515109 PMCID: PMC9748595 DOI: 10.1093/jee/toac151] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/13/2022] [Indexed: 06/16/2023]
Abstract
The fall armyworm (FAW) Spodoptera frugiperda (Smith; Lepidoptera: Noctuidae) is present in over 70 countries in Africa, Asia, and Oceania. Its rapid dispersal since 2016 when it was first reported in western Africa, and associated devastation to agricultural productivity, highlight the challenges posed by this pest. Currently, its management largely relies on insecticide sprays and transgenic Bacillus thuringiensis toxins, therefore understanding their responses to these agents and characteristics of any resistance genes enables adaptive strategies. In Australia, S. frugiperda was reported at the end of January 2020 in northern Queensland and by March 2020, also in northern Western Australia. As an urgent first response we undertook bioassays on two Australian populations, one each from these initial points of establishment. To assist with preliminary sensitivity assessment, two endemic noctuid pest species, Helicoverpa armigera (Hübner; Lepidoptera, Noctuidae) and Spodoptera litura (Fabricius; Lepidoptera, Noctuidae), were concurrently screened to obtain larval LC50 estimates against various insecticides. We characterized known resistance alleles from the VGSC, ACE-1, RyR, and ABCC2 genes to compare with published allele frequencies and bioassay responses from native and invasive S. frugiperda populations. An approximately 10× LC50 difference for indoxacarb was detected between Australian populations, which was approximately 28× higher than that reported from an Indian population. Characterization of ACE-1 and VGSC alleles provided further evidence of multiple introductions in Asia, and multiple pathways involving genetically distinct individuals in Australia. The preliminary bioassay results and resistance allele patterns from invasive S. frugiperda populations suggest multiple introductions have contributed to the pest's spread and challenge the axiom of its rapid 'west-to-east' spread.
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Affiliation(s)
- W T Tay
- CSIRO Black Mountain Laboratories, Clunies Ross Street, Acton, ACT 2601, Australia
- Applied BioSciences, Macquarie University, Sydney, NSW 2100, Australia
| | - R V Rane
- Applied BioSciences, Macquarie University, Sydney, NSW 2100, Australia
- CSIRO, 343 Royal Parade, Parkville, VIC 3052, Australia
| | - W James
- CSIRO Black Mountain Laboratories, Clunies Ross Street, Acton, ACT 2601, Australia
| | - K H J Gordon
- CSIRO Black Mountain Laboratories, Clunies Ross Street, Acton, ACT 2601, Australia
| | - S Downes
- CSIRO McMaster Laboratories, New England Highway, Armidale, NSW 2350, Australia
| | - J Kim
- College of Agriculture and Life Science, Kangwon National University, Republic of Korea
| | | | - T K Walsh
- CSIRO Black Mountain Laboratories, Clunies Ross Street, Acton, ACT 2601, Australia
- Applied BioSciences, Macquarie University, Sydney, NSW 2100, Australia
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Walsh TK, Heckel DG, Wu Y, Downes S, Gordon KHJ, Oakeshott JG. Determinants of Insecticide Resistance Evolution: Comparative Analysis Among Heliothines. ANNUAL REVIEW OF ENTOMOLOGY 2022; 67:387-406. [PMID: 34995087 DOI: 10.1146/annurev-ento-080421-071655] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
It is increasingly clear that pest species vary widely in their propensities to develop insecticide resistance. This review uses a comparative approach to analyze the key pest management practices and ecological and biochemical or genetic characteristics of the target that contribute to this variation. We focus on six heliothine species, three of which, Helicoverpa armigera, Heliothis virescens, and Helicoverpa zea, have developed resistances to many pesticide classes. The three others, Helicoverpa punctigera, Helicoverpa assulta, and Helicoverpa gelotopoeon, also significant pests, have developed resistance to very few pesticide classes. We find that host range and movement between alternate hosts are key ecological traits that influence effective selection intensities for resistance. Operational issues are also critical; area-wide, cross-pesticide management practices that account for these ecological factors are key to reducing selection intensity. Without such management, treatment using broad-spectrum chemicals serves to multiply the effects of host plant preference, preadaptive detoxification ability, and high genetic diversity to create a pesticide treadmill for the three high-propensity species.Without rigorous ongoing management, such a treadmill could still develop for newer, more selective chemistries and insecticidal transgenic crops.
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Affiliation(s)
- T K Walsh
- CSIRO Black Mountain Laboratories, Canberra, Australian Capital Territory, Australia;
- Applied BioSciences, Macquarie University, Sydney, New South Wales, Australia
| | - D G Heckel
- Department of Entomology, Max Planck Institute for Chemical Ecology, Jena, Germany
| | - Yidong Wu
- Key Laboratory of Plant Immunity and College of Plant Protection, Nanjing Agricultural University, Nanjing, China
| | - S Downes
- CSIRO McMaster Laboratories, Armidale, New South Wales, Australia
| | - K H J Gordon
- CSIRO Black Mountain Laboratories, Canberra, Australian Capital Territory, Australia;
| | - J G Oakeshott
- CSIRO Black Mountain Laboratories, Canberra, Australian Capital Territory, Australia;
- Applied BioSciences, Macquarie University, Sydney, New South Wales, Australia
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Knight KM, Head GP, Rogers DJ. Successful development and implementation of a practical proactive resistance management plan for Bt cotton in Australia. PEST MANAGEMENT SCIENCE 2021; 77:4262-4273. [PMID: 34041838 DOI: 10.1002/ps.6490] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/07/2020] [Revised: 03/24/2021] [Accepted: 05/27/2021] [Indexed: 06/12/2023]
Abstract
This article describes the design and > 20 years of effective implementation of a proactive resistance-management plan for transgenic Bacillus thuringiensis (Bt) cotton that targets Helicoverpa armigera (Hübner) and Helicoverpa punctigera (Wallengren) in Australia, considering pest biology and ecology, insights from resistance-evolution modelling, and the importance of the human component to effective implementation. This is placed in the context of processes associated with adaptive resource management. Bt cotton has provided Australian cotton growers with technology to manage Helicoverpa species that previously challenged the industry's viability, while at the same time resulting in no detectable changes in the resistance allele frequency in field populations of either Helicoverpa species in eastern Australia. This is the most long-lived and successful global example of a proactive resistance management plan for an insect pest. Six key learnings important to the successful development and implementation of a proactive transgenic-crop resistance management plan are: the programme has to have a strong science base; there has to be broad stakeholder support at all levels; there has to be a strong implementation programme; the plan needs to be supported by auditing and enforced remediation of deviations from the mandated resistance management plan; A programme of rigorous and on-going resistance allele monitoring; an attitude of continuous improvement for all aspects of the resistance management plan. The lessons learnt from the deployment of Bt cotton in Australia are relevant globally and provide important guidelines for the deployment of transgenic crops for insect control wherever they are grown. © 2021 Society of Chemical Industry.
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Affiliation(s)
| | | | - D John Rogers
- Research Connections and Consulting, St Lucia, Australia
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Windus LCE, Jones AM, Downes S, Walsh T, Knight K, Kinkema M. HearNPV susceptibility in Helicoverpa armigera and Helicoverpa punctigera strains resistant to Bt toxins Cry1Ac, Cry2Ab, and Vip3Aa. J Invertebr Pathol 2021; 183:107598. [PMID: 33957131 DOI: 10.1016/j.jip.2021.107598] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2021] [Revised: 04/22/2021] [Accepted: 04/24/2021] [Indexed: 10/21/2022]
Abstract
Genetically engineered crops expressing insecticidal toxins from Bacillus thuringiensis (Bt) have improved the management of targeted lepidopteran pests and reduced the use of insecticide sprays. These benefits explain an increasing adoption of Bt crops worldwide, intensifying the selection pressure on target species and the risk of resistance. Nucleopolyhedroviruses (NPVs) are effective bioinsecticides against numerous important lepidopteran pests. If Bt-resistant insects are shown to be susceptible to NPVs then these bioinsecticides could be a valuable component of Insecticide Resistance Management (IRM) strategies for Bt crops. We assessed the effectiveness of a Helicoverpa nucleopolyhedrovirus (HearNPV) against several different Bt-resistant strains. Utilising a droplet feeding bioassay we confirmed susceptibility to HearNPV in Helicoverpa punctigera and Helicoverpa armigera larvae resistant to the Bt toxins Cry1Ac, Cry2Ab, and Vip3A. Dual resistant H. punctigera, (Cry1Ac/Cry2Ab, and Cry2Ab/Vip3A) and dual resistant H. armigera (Cry2Ab/Vip3A) were also susceptible to HearNPV. Regardless of their specific resistance profile, Bt-resistant larvae displayed statistically similar lethal concentration (LC50) and lethal time (LT50) responses to HearNPV when compared to Bt-sensitive control insects. These results indicate that Bt-resistant H. armigera and H. punctigera are not cross-resistant to HearNPV. Consequently, the use of HearNPV against these pests may be a valuable tool to an IRM strategy for controlling Bt-resistant populations.
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Affiliation(s)
| | - Adele M Jones
- AgBiTech, 8 Rocla Court, Glenvale, QLD 4350, Australia
| | - Sharon Downes
- CSIRO Agriculture and Food, Australian Cotton Research Institute, 21888 Kamilaroi Highway, Narrabri, NSW 2390, Australia
| | - Tom Walsh
- CSIRO Land and Water, Black Mountain Laboratories, Clunies Ross Street, Black Mountain, ACT 2601, Australia
| | - Kristen Knight
- Bayer Crop Science, McDougall Street, Glenvale, QLD 4350, Australia
| | - Mark Kinkema
- AgBiTech, 14401 Sovereign Rd, Fort Worth, TX 76155, USA.
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Rendon D, Taylor PW, Whitehouse MEA. Multiple intraguild predators reduce mortality risk of a mutual agricultural pest prey in simple, but not in complex, experimental settings. AUSTRAL ECOL 2019. [DOI: 10.1111/aec.12773] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Dalila Rendon
- CSIRO Agriculture and Food; Australian Cotton Research Institute; 21888 Kamilaroi Hwy Narrabri New South Wales 2390 Australia
- Department of Biological Sciences; Macquarie University; Sydney New South Wales Australia
| | - Phillip W. Taylor
- Department of Biological Sciences; Macquarie University; Sydney New South Wales Australia
| | - Mary E. A. Whitehouse
- CSIRO Agriculture and Food; Australian Cotton Research Institute; 21888 Kamilaroi Hwy Narrabri New South Wales 2390 Australia
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Bird LJ, Walker PW. Baseline Susceptibility of Helicoverpa punctigera (Lepidoptera: Noctuidae) to Indoxacarb, Emamectin Benzoate, and Chlorantraniliprole. JOURNAL OF ECONOMIC ENTOMOLOGY 2019; 112:818-826. [PMID: 30566638 DOI: 10.1093/jee/toy389] [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: 08/26/2018] [Indexed: 06/09/2023]
Abstract
Susceptibility in Helicoverpa punctigera (Wallengren) to emamectin benzoate, chlorantraniliprole, and indoxacarb was established from feeding assays on insecticide-incorporated artificial diet in the laboratory. The variation in dose responses was examined in H. punctigera field populations collected in eastern Australia between September 2013 and January 2016 and compared with a laboratory strain. Chlorantraniliprole was the most toxic insecticide with an average LC50 of 3.7 µg of insecticide per liter of diet (n = 12 field strains). The average LC50 for emamectin benzoate was 5.6 µg of insecticide per liter of diet (n = 11 field strains), whereas indoxacarb had the lowest toxicity with an average LC50 of 172 µg of insecticide per liter of diet (n = 14 field strains). Variation in susceptibility between field strains was low at 1.9-, 2.4-, and 2-fold for chlorantraniliprole, emamectin benzoate, and indoxacarb, respectively. Narrow ranges of intra-specific tolerance, high slopes, and goodness-of-fit to a probit binomial model suggested feeding bioassays using insecticide-incorporated diet were a more effective laboratory method for measuring dose responses of these insecticides in H. punctigera than traditional topical bioassays. We propose discriminating concentrations of 0.032, 0.026, and 4 µg of insecticide/ml of diet for chlorantraniliprole, emamectin benzoate, and indoxacarb, respectively, to monitor insecticide resistance in H. punctigera. Although the potential for H. punctigera to develop insecticide resistance is considered low based on historical records, recent changes in population dynamics of this species in eastern Australia may have increased the risk of resistance development.
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Affiliation(s)
- Lisa J Bird
- NSW Department of Primary Industries, Tamworth Agricultural Institute, Calala, Australia
| | - Paul W Walker
- NSW Department of Primary Industries, Tamworth Agricultural Institute, Calala, Australia
- Tasmanian Institute of Agriculture, University of Tasmania, Hobart, Australia
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Xiao Y, Wu K. Recent progress on the interaction between insects and Bacillus thuringiensis crops. Philos Trans R Soc Lond B Biol Sci 2019; 374:20180316. [PMID: 30967027 PMCID: PMC6367150 DOI: 10.1098/rstb.2018.0316] [Citation(s) in RCA: 60] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/05/2018] [Indexed: 11/13/2022] Open
Abstract
Extensive use of chemical pesticides poses a great threat to the environment and food safety. The discovery of Bacillus thuringiensis (Bt) toxins with effective insecticidal activity against pests and the development of transgenic technology of plants opened a new era of pest control. Transgenic Bt crops, including maize, cotton and soya bean, have now been produced and commercialized to protect against about 30 major coleopteran and lepidopteran pests, greatly benefiting the environment and the economy. However, with the long-term cultivation of Bt crops, some target pests have gradually developed resistance. Numerous studies have indicated that mutations in genes for toxins activation, toxin-binding and insect immunization are important sources in Bt resistance. An in-depth exploration of the corresponding Bt-resistance mechanisms will aid in the design of new strategies to prevent and control pests. Future research will focus on Bt crops expressing new genes and multiple genes to control a broader range of pests as part of an integrated pest management programme. This article is part of the theme issue 'Biotic signalling sheds light on smart pest management'.
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Affiliation(s)
- Yutao Xiao
- Agricultural Genomics Institute at Shenzhen, Chinese Academy of Agricultural Sciences, Shenzhen 518120, People's Republic of China
| | - Kongming Wu
- The State Key Laboratory for Biology of Plant Disease and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, West Yuanmingyuan Road, Beijing 100193, People's Republic of China
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Baker GH, Tann CR, Verwey P, Lisle L. Do the plant host origins of Helicoverpa (Lepidoptera: Noctuidae) moth populations reflect the agricultural landscapes within which they are caught? BULLETIN OF ENTOMOLOGICAL RESEARCH 2019; 109:1-14. [PMID: 29704901 DOI: 10.1017/s0007485318000214] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
The use of Bt cotton varieties has greatly reduced the amount of conventional insecticides required to control lepidopteran pests, Helicoverpa armigera and Helicoverpa punctigera, in Australia, but the possibility that these moths might become resistant to Bt remains a threat. Consequently, a Resistance Management Plan, which includes the mandatory growing of refuge crops (pigeon pea and non-Bt cotton; both C3 plants), has been established for Bt cotton farmers. However, knowledge of the relative contributions made to overall moth populations from the many host origins (both C3 and C4 plants) available to these insects throughout cotton production regions remains limited, as do the scales of movement and spatial mixing of moths within and between these areas. This study used stable isotope signatures (in particular δ13C) to help identify where moths fed as larvae within separate cotton production regions which differed in their proportions of C3 and C4 host crops (e.g. cotton and sorghum, respectively). C3-derived moths predominated in the early season, but C4-derived moths increased in frequency later. The overall proportion of C4 moths was higher in H. armigera than in H. punctigera. Whilst the relative proportions of C3 and C4 moths differed between regions, no differences in such proportiorns were found at smaller spatial scales, nor were there significant correlations between crop composition and isotope signatures in moths. Overall, these results suggest that C4 host plants are likely to be very important in offsetting the development of Bt resistance in these insects and such influences may operate across multiple regions within a single growing season.
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Affiliation(s)
- G H Baker
- CSIRO Health & Biosecurity,GPO Box 1700,Canberra,A.C.T. 2601,Australia
| | - C R Tann
- CSIRO Agriculture & Food,Locked Bag 59,Narrabri,N.S.W. 2390,Australia
| | - P Verwey
- NSW Department of Primary Industries,Locked Bag 1000,Narrabri,N.S.W. 2390,Australia
| | - L Lisle
- Environmental & Rural Science,University of New England,Armidale,N.S.W. 2351,Australia
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Rendon D, Taylor PW, Wilder SM, Whitehouse MEA. Does prey encounter and nutrient content affect prey selection in wolf spiders inhabiting Bt cotton fields? PLoS One 2019; 14:e0210296. [PMID: 30629650 PMCID: PMC6328153 DOI: 10.1371/journal.pone.0210296] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2018] [Accepted: 12/18/2018] [Indexed: 11/29/2022] Open
Abstract
Wolf spiders are abundant and voracious predators at the soil-plant interface in cotton crops. Among other prey, they attack late-instar larvae of the cotton bollworm Helicoverpa spp., an economically important pest. Consequently, wolf spiders in transgenic Bt cotton could provide significant biological control of Bt-resistant Helicoverpa larvae that descend to the soil to pupate. The predator-prey interactions between wolf spiders and Helicoverpa could, however, be constrained by the presence of alternative prey and intraguild predators. This study used laboratory enclosures to analyse the effect of alternative prey on predatory selection of the wolf spider Tasmanicosa leuckartii Thorell. The prey included another wolf spider Hogna crispipes Koch (potential intraguild predator), the ground cricket Teleogryllus commodus Walker (minor pest), and Helicoverpa armigera larvae (major pest). We tested if encounter rates, prey vulnerability, and prey nutritional content influenced the likelihood that a prey was attacked. In three-way food webs, Tasmanicosa encountered and attacked Teleogryllus and Helicoverpa in similar frequencies. However, in the presence of a competing intraguild predator and potential prey (Hogna) in a four-way food web, Tasmanicosa did not always attack Teleogryllus at first encounter, but still attacked Helicoverpa at each encounter. Helicoverpa (protein-poor) and Hogna (protein-rich) were consumed by Tasmanicosa in similar proportions, suggesting that Tasmanicosa might benefit from nutrient balance as an outcome of diverse prey in this food web. As Teleogryllus (protein rich) escapes quicker than Helicoverpa and Hogna, Hogna may be an easier protein-rich option than Teleogryllus. Field surveys showed that while Teleogryllus was the most common prey, wolf spiders feed on diverse insect taxa, as well as other spiders. That Tasmanicosa readily attacked Helicoverpa larvae in the presence of alternative prey is an encouraging result that supports the potential of Tasmanicosa predation to assist in the control of Bt-resistant Helicoverpa larvae and thereby inhibit the proliferation and spread of resistance.
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Affiliation(s)
- Dalila Rendon
- CSIRO Agriculture and Food, Australian Cotton Research Institute, Narrabri NSW, Australia
- Department of Biological Sciences, Macquarie University, Sydney NSW, Australia
| | - Phillip W. Taylor
- Department of Biological Sciences, Macquarie University, Sydney NSW, Australia
| | - Shawn M. Wilder
- Department of Integrative Biology, Oklahoma State University, Stillwater OK, United States of America
| | - Mary E. A. Whitehouse
- CSIRO Agriculture and Food, Australian Cotton Research Institute, Narrabri NSW, Australia
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Walsh T, James B, Chakroun M, Ferré J, Downes S. Isolating, characterising and identifying a Cry1Ac resistance mutation in field populations of Helicoverpa punctigera. Sci Rep 2018; 8:2626. [PMID: 29422629 PMCID: PMC5805676 DOI: 10.1038/s41598-018-21012-w] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2017] [Accepted: 01/12/2018] [Indexed: 11/09/2022] Open
Abstract
Transgenic cotton expressing insecticidal proteins from Bacillus thuringiensis (Bt) has been grown in Australia for over 20 years and resistance remains the biggest threat. The native moth, Helicoverpa punctigera is a significant pest of cotton. A genotype causing resistance to Cry1Ac in H. punctigera was isolated from the field and a homozygous line established. The phenotype is recessive and homozygous individuals possess 113 fold resistance to Cry1Ac. Individuals that carry Cry1Ac resistance genes are rare in Australia with a frequency of 0.033 being detected in field populations. RNAseq, RT-PCR and DNA sequencing reveals a single nucleotide polymorphism at a splice site in the cadherin gene as the causal mutation, resulting in the partial transcription of the intron and a premature stop codon. Analysis of Cry1Ac binding to H. punctigera brush border membrane vesicles showed that it is unaffected by the disrupted cadherin gene. This suggests that the major Cry1Ac target is not cadherin but that this molecule plays a key role in resistance and therefore the mode of action. This work adds to our knowledge of resistance mechanisms in H. punctigera and the growing literature around the role of cadherin in the mode of action of Cry1 type Bt proteins.
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Affiliation(s)
- Tom Walsh
- CSIRO, Black Mountain Laboratories, Canberra, ACT, 2601, Australia.
| | - Bill James
- CSIRO, Black Mountain Laboratories, Canberra, ACT, 2601, Australia
| | - Maissa Chakroun
- ERI of Biotechnology and Biomedicine (BIOTECMED), Universitat de València, Burjassot, 46100, Spain
| | - Juan Ferré
- ERI of Biotechnology and Biomedicine (BIOTECMED), Universitat de València, Burjassot, 46100, Spain
| | - Sharon Downes
- CSIRO, Myall Vale Laboratories, Kamilaroi Highway, Narrabri, NSW 2390, Australia
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Santos-Amaya OF, Tavares CS, Rodrigues JVC, Souza TC, Rodrigues-Silva N, Guedes RNC, Alves AP, Pereira EJG. Magnitude and Allele Frequency of Cry1F Resistance in Field Populations of the Fall Armyworm (Lepidoptera: Noctuidae) in Brazil. JOURNAL OF ECONOMIC ENTOMOLOGY 2017; 110:1770-1778. [PMID: 28535300 DOI: 10.1093/jee/tox146] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/15/2016] [Indexed: 06/07/2023]
Abstract
Bacillus thuringiensis (Bt) corn producing the Cry1F protein was the first highly efficacious Bt corn deployed against the fall armyworm Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) in Brazil, but reduced efficacy of this technology against the fall armyworm has been reported in some regions of the country. Here, we surveyed Cry1F resistance allele frequency and susceptibility of eight S. frugiperda populations collected in 2013 from non-Bt fields in different regions of Brazil. In F1 screen experiments, the overall frequency of the Cry1F resistance alleles in Brazilian populations was estimated at 0.24, with 95% credibility interval between 0.18 and 0.25. In concentration-response bioassays, five of the eight populations surveyed exhibited significant resistance levels, which were over 32 times higher than that of the standard susceptible laboratory strain. The estimates of Cry1F resistance allele frequency were positively correlated with those of median effective or lethal concentrations (i.e., EC50 or LC50). These results show that the allelic frequency and the magnitude of Cry1F resistance are high in field populations of S. frugiperda in Brazil, indicating a challenging situation for resistance management.
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Affiliation(s)
- O F Santos-Amaya
- Departament of Entomology, Universidade Federal de Viçosa, Viçosa, MG 36570-900, Brazil
| | - C S Tavares
- Departament of Entomology, Universidade Federal de Viçosa, Viçosa, MG 36570-900, Brazil
| | - J V C Rodrigues
- Departament of Entomology, Universidade Federal de Viçosa, Viçosa, MG 36570-900, Brazil
| | - T C Souza
- Departament of Entomology, Universidade Federal de Viçosa, Viçosa, MG 36570-900, Brazil
| | - N Rodrigues-Silva
- Departament of Entomology, Universidade Federal de Viçosa, Viçosa, MG 36570-900, Brazil
| | - R N C Guedes
- Departament of Entomology, Universidade Federal de Viçosa, Viçosa, MG 36570-900, Brazil
| | - A P Alves
- DuPont Pioneer, 7300 NW 62nd Ave., Johnston, IA 50131
| | - E J G Pereira
- Departament of Entomology, Universidade Federal de Viçosa, Viçosa, MG 36570-900, Brazil
- National Institute of Science and Technology in Plant-Pest Interactions, Universidade Federal de Viçosa, Viçosa, MG 36570-900, Brazil
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Baker GH, Tann CR. Long-term changes in the numbers of Helicoverpa punctigera (Lepidoptera: Noctuidae) in a cotton production landscape in northern New South Wales, Australia. BULLETIN OF ENTOMOLOGICAL RESEARCH 2017; 107:174-187. [PMID: 27829483 DOI: 10.1017/s0007485316000821] [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] [Indexed: 06/06/2023]
Abstract
Two noctuid moths, Helicoverpa punctigera and Helicoverpa armigera, are pests of several agricultural crops in Australia, most notably cotton. Cotton is a summer crop, grown predominantly in eastern Australia. The use of transgenic (Bt) cotton has reduced the damage caused by Helicoverpa spp., but the development of Bt resistance in these insects remains a threat. In the past, large populations of H. punctigera have built up in inland Australia, following autumn-winter rains. Moths have then migrated to the cropping regions in spring, when their inland host plants dried off. To determine if there have been any long-term changes in this pattern, pheromone traps were set for H. punctigera throughout a cropping landscape in northern New South Wales from 1992 to 2015. At least three generations of moths were caught from spring to autumn. The 1st generation (mostly spring migrants) was the most numerous. Trap captures varied between sites and decreased in time, especially for moths in the 1st generation. Nearby habitat type influenced the size of catch and there was some evidence that local weather also influenced the numbers of moths caught. There was no correlation between trap catches in the cropping region and rainfall in the inland. In addition, there was little evidence that Bt cotton has reduced the abundance of H. punctigera at landscape scale. The apparent decline in the number of presumably Bt susceptible moths arriving each spring in the cropping regions from inland habitats is of concern in relation to the management of Bt resistance.
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Affiliation(s)
- G H Baker
- CSIRO Agriculture and Food,GPO Box 1700,Canberra,A.C.T. 2601,Australia
| | - C R Tann
- CSIRO Agriculture and Food, Locked Bag 59,Narrabri,N.S.W. 2390,Australia
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13
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Baker GH, Tann CR. Broad-scale suppression of cotton bollworm, Helicoverpa armigera (Lepidoptera: Noctuidae), associated with Bt cotton crops in Northern New South Wales, Australia. BULLETIN OF ENTOMOLOGICAL RESEARCH 2017; 107:188-199. [PMID: 27876099 DOI: 10.1017/s0007485316000912] [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] [Indexed: 05/25/2023]
Abstract
The cotton bollworm, Helicoverpa armigera, is a major pest of many agricultural crops in several countries, including Australia. Transgenic cotton, expressing a single Bt toxin, was first used in the 1990s to control H. armigera and other lepidopteran pests. Landscape scale or greater pest suppression has been reported in some countries using this technology. However, a long-term, broad-scale pheromone trapping program for H. armigera in a mixed cropping region in eastern Australia caught more moths during the deployment of single Bt toxin cotton (Ingard®) (1996-2004) than in previous years. This response can be attributed, at least in part, to (1) a precautionary cap (30% of total cotton grown, by area) being applied to Ingard® to restrict the development of Bt resistance in the pest, and (2) during the Ingard® era, cotton production greatly increased (as did that of another host plant, sorghum) and H. armigera (in particular the 3rd and older generations) responded in concert with this increase in host plant availability. However, with the replacement of Ingard® with Bollgard II® cotton (containing two different Bt toxins) in 2005, and recovery of the cotton industry from prevailing drought, H. armigera failed to track increased host-plant supply and moth numbers decreased. Greater toxicity of the two gene product, introduction of no cap on Bt cotton proportion, and an increase in natural enemy abundance are suggested as the most likely mechanisms responsible for the suppression observed.
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Affiliation(s)
- G H Baker
- CSIRO Agriculture & Food,GPO Box 1700, Canberra,ACT 2601,Australia
| | - C R Tann
- CSIRO Agriculture & Food,Locked Bag 59, Narrabri,NSW 2390,Australia
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Yano SA, Specht A, Moscardi F, Carvalho RA, Dourado PM, Martinelli S, Head GP, Sosa-Gómez DR. High susceptibility and low resistance allele frequency of Chrysodeixis includens (Lepidoptera: Noctuidae) field populations to Cry1Ac in Brazil. PEST MANAGEMENT SCIENCE 2016; 72:1578-84. [PMID: 26581167 DOI: 10.1002/ps.4191] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/28/2015] [Revised: 11/13/2015] [Accepted: 11/13/2015] [Indexed: 06/05/2023]
Abstract
BACKGROUND The soybean looper (SBL), Chrysodeixis includens (Walker), is one of the most important soybean pests in Brazil. MON 87701 × MON 89788 soybean expressing Cry1Ac has been recently deployed in Brazil, providing high levels of control against the primary lepidopteran pests. To support insect resistance management (IRM) programmes, the baseline susceptibility of SBL to Cry1Ac was assessed, and the resistance allele frequency was estimated on the basis of an F2 screen. RESULTS The toxicity (LC50 ) of Cry1Ac ranged from 0.39 to 2.01 µg mL(-1) diet among all SBL field populations collected from crop seasons 2008/09 to 2012/13, which indicated approximately fivefold variation. Cry1Ac diagnostic concentrations of 5.6 and 18 µg mL(-1) diet were established for monitoring purposes, and no shift in mortality was observed. A total of 626 F2 family lines derived from SBL collected from locations across Brazil during crop season 2014/15 were screened for the presence of Cry1Ac resistance alleles. None of the 626 families survived on MON 87701 × MON 89788 soybean leaf tissue (joint frequency 0.0004). CONCLUSIONS SBL showed high susceptibility and low resistance allele frequency to Cry1Ac across the main soybean-producing regions in Brazil. These findings meet important criteria for effective IRM strategy. © 2015 Society of Chemical Industry.
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F2 screen for resistance to Bacillus thuringiensis Cry2Ab2-maize in field populations of Spodoptera frugiperda (Lepidoptera: Noctuidae) from the southern United States. J Invertebr Pathol 2016; 138:66-72. [DOI: 10.1016/j.jip.2016.06.005] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2016] [Revised: 05/31/2016] [Accepted: 06/13/2016] [Indexed: 11/18/2022]
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Tay WT, Beckett SJ, De Barro PJ. Phosphine resistance in Australian Cryptolestes species (Coleoptera: Laemophloeidae): perspectives from mitochondrial DNA cytochrome oxidase I analysis. PEST MANAGEMENT SCIENCE 2016; 72:1250-1259. [PMID: 24753308 DOI: 10.1002/ps.3805] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2013] [Revised: 04/14/2014] [Accepted: 04/14/2014] [Indexed: 06/03/2023]
Abstract
BACKGROUND The flat grain beetle (FGB) species Cryptolestes ferrugineus, C. pusillus, C. pusilloides and C. turcicus are major stored-product pests worldwide, of which the first three are present in Australia. C. ferrugineus is also a species with high phosphine resistance status in various countries. Morphological identification of Cryptolestes species is difficult and represents an additional barrier to effective management of phosphine resistance in FGBs. RESULT Mitochondrial DNA cytochrome oxidase I (mtDNA COI) gene characterisation enabled differentiation of the four major FGB pest species through direct sequence comparison, and enabled the development of a PCR-RFLP method for rapid species differentiation. We detected two mtDNA haplotypes (Cunk-01, 02) present at low frequencies with an average nucleotide divergence rate of 0.079 ± 0.011 (SE) from C. pusillus. This nucleotide divergence rate is similar to that between C. ferrugineus and C. pusilloides (0.088 ± 0.012). Male and female genitalia morphologies of the Cunk-02 individuals indicated they were consistent with C. pusillus, yet DNA sequence analyses suggested species-level divergence. The mtDNA COI gene of phosphine-bioassayed, lab-reared F1 generation survivors supported the presence of strong phosphine resistance in C. ferrugineus, but unexpectedly also in C. pusilloides and C. pusillus F1 survivors. CONCLUSION We demonstrated the utility of molecular DNA techniques for differentiating closely related insect species, and its usefulness in assisting the management of pest insect species. The likely presence of a cryptic C. pusillus species in Australia and the possible development of strong phosphine resistance in Australian FGB pest species require further investigation. © 2014 Society of Chemical Industry.
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Affiliation(s)
- Wee Tek Tay
- Biosecurity Flagship, CSIRO Ecosystem Sciences, Black Mountain Laboratories, ACT, Australia
- Plant Biosecurity Cooperative Research Centre, Bruce, ACT, Australia
| | - Stephen J Beckett
- Biosecurity Flagship, CSIRO Ecosystem Sciences, Black Mountain Laboratories, ACT, Australia
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Tay WT, Mahon RJ, Heckel DG, Walsh TK, Downes S, James WJ, Lee SF, Reineke A, Williams AK, Gordon KHJ. Insect Resistance to Bacillus thuringiensis Toxin Cry2Ab Is Conferred by Mutations in an ABC Transporter Subfamily A Protein. PLoS Genet 2015; 11:e1005534. [PMID: 26583651 PMCID: PMC4652872 DOI: 10.1371/journal.pgen.1005534] [Citation(s) in RCA: 122] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2015] [Accepted: 08/25/2015] [Indexed: 12/15/2022] Open
Abstract
The use of conventional chemical insecticides and bacterial toxins to control lepidopteran pests of global agriculture has imposed significant selection pressure leading to the rapid evolution of insecticide resistance. Transgenic crops (e.g., cotton) expressing the Bt Cry toxins are now used world wide to control these pests, including the highly polyphagous and invasive cotton bollworm Helicoverpa armigera. Since 2004, the Cry2Ab toxin has become widely used for controlling H. armigera, often used in combination with Cry1Ac to delay resistance evolution. Isolation of H. armigera and H. punctigera individuals heterozygous for Cry2Ab resistance in 2002 and 2004, respectively, allowed aspects of Cry2Ab resistance (level, fitness costs, genetic dominance, complementation tests) to be characterised in both species. However, the gene identity and genetic changes conferring this resistance were unknown, as was the detailed Cry2Ab mode of action. No cross-resistance to Cry1Ac was observed in mutant lines. Biphasic linkage analysis of a Cry2Ab-resistant H. armigera family followed by exon-primed intron-crossing (EPIC) marker mapping and candidate gene sequencing identified three independent resistance-associated INDEL mutations in an ATP-Binding Cassette (ABC) transporter gene we named HaABCA2. A deletion mutation was also identified in the H. punctigera homolog from the resistant line. All mutations truncate the ABCA2 protein. Isolation of further Cry2Ab resistance alleles in the same gene from field H. armigera populations indicates unequal resistance allele frequencies and the potential for Bt resistance evolution. Identification of the gene involved in resistance as an ABC transporter of the A subfamily adds to the body of evidence on the crucial role this gene family plays in the mode of action of the Bt Cry toxins. The structural differences between the ABCA2, and that of the C subfamily required for Cry1Ac toxicity, indicate differences in the detailed mode-of-action of the two Bt Cry toxins. Transgenic crops expressing the insecticidal protein Cry2Ab from Bacillus thuringiensis (Bt) are used worldwide to suppress damage by lepidopteran pests, often used in combination with Cry1Ac toxin to delay resistance evolution. Until now, the Cry2Ab mode of action and the mechanism of resistance were unknown, with field-isolated Cry2Ab resistant Helicoverpa armigera showing no cross-resistance to Cry1Ac. In this study, biphasic linkage analysis of a Cry2Ab-resistant H. armigera family followed by EPIC marker mapping and candidate gene sequencing identified three independent INDEL mutations in an ATP-Binding Cassette transporter subfamily A gene (ABCA2). A deletion mutation was identified in the same gene of resistant H. punctigera. All four mutations are predicted to truncate the ABCA2 protein. This is the first molecular genetic characterization of insect resistance to the Cry2Ab toxin, and detection of diverse Cry2Ab resistance alleles will contribute to understanding the micro-evolutionary processes that underpinned lepidopteran Bt-resistance.
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Affiliation(s)
- Wee Tek Tay
- CSIRO, Black Mountain Laboratories, Canberra, Australian Capital Territory, Australia
- * E-mail:
| | - Rod J. Mahon
- CSIRO, Black Mountain Laboratories, Canberra, Australian Capital Territory, Australia
| | - David G. Heckel
- Department of Entomology, Max-Planck Institute for Chemical Ecology, Beutenberg Campus, Jena, Germany
| | - Thomas K. Walsh
- CSIRO, Black Mountain Laboratories, Canberra, Australian Capital Territory, Australia
| | - Sharon Downes
- CSIRO, Australian Cotton Research Institute, Narrabri, New South Wales, Australia
| | - William J. James
- CSIRO, Black Mountain Laboratories, Canberra, Australian Capital Territory, Australia
| | - Sui-Fai Lee
- Department of Genetics, University of Melbourne, Parkville, Victoria, Australia
| | - Annette Reineke
- Institute for Phytomedicine, Center of Applied Biology, Geisenheim University, Geiesenheim, Germany
| | - Adam K. Williams
- Department of Genetics, University of Melbourne, Parkville, Victoria, Australia
| | - Karl H. J. Gordon
- CSIRO, Black Mountain Laboratories, Canberra, Australian Capital Territory, Australia
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Baker GH, Tann CR. Mating of Helicoverpa armigera (Lepidoptera: Noctuidae) moths and their host plant origins as larvae within Australian cotton farming systems. BULLETIN OF ENTOMOLOGICAL RESEARCH 2013; 103:171-181. [PMID: 22999440 DOI: 10.1017/s0007485312000508] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Transgenic (Bt) cotton dominates Australian cotton production systems. It is grown to control feeding damage by lepidopteran pests such as Helicoverpa armigera. The possibility that these moths might become resistant to Bt remains a threat. Consequently, refuge crops (with no Bt) must be grown with Bt cotton to produce large numbers of Bt-susceptible moths to reduce the risk of resistance developing. A key assumption of the refuge strategy, that moths from different host plant origins mate at random, remains untested. During the period of the study reported here, refuge crops included pigeon pea, conventional cotton (C3 plants), sorghum or maize (C4 plants). To identify the relative contributions made by these (and perhaps other) C3 and C4 plants to populations of H. armigera in cotton landscapes, we measured stable carbon isotopes (δ(13)C) within individual moths captured in the field. Overall, 53% of the moths were of C4 origin. In addition, we demonstrated, by comparing the stable isotope signatures of mating pairs of moths, that mating is indeed random amongst moths of different plant origins (i.e. C3 and C4). Stable nitrogen isotope signatures (δ(15)N) were recorded to further discriminate amongst host plant origins (e.g. legumes from non-legumes), but such measurements proved generally unsuitable. Since 2010, maize and sorghum are no longer used as dedicated refuges in Australia. However, these plants remain very common crops in cotton production regions, so their roles as 'unstructured' refuges seem likely to be significant.
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Affiliation(s)
- G H Baker
- CSIRO Ecosystem Sciences and Cotton Catchment Communities Cooperative Research Centre, Canberra, ACT, Australia.
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Sohail MN, Karimi SM, Asad S, Mansoor S, Zafar Y, Mukhtar Z. Development of broad-spectrum insect-resistant tobacco by expression of synthetic cry1Ac and cry2Ab genes. Biotechnol Lett 2012; 34:1553-60. [PMID: 22488439 DOI: 10.1007/s10529-012-0923-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2012] [Accepted: 03/23/2012] [Indexed: 10/28/2022]
Abstract
Efficacy of two newly synthesized cry1Ac and cry2Ab genes was checked in tobacco before their expression in cotton. Both genes were artificially synthesized and codon optimized with respect to cotton-preferred codon usage. These genes were cloned in a plant expression vector and then transformed into tobacco. Fifty-eight putative transgenic plants were recovered from the selected explants. Successful integration of both genes in plant genome was confirmed by PCR amplification. Expression of transgenes was confirmed by PCR amplification from total plant RNA. Detached leaf insect bioassays were conducted with Helicoverpa armigera and Spodoptera exigua larvae. About 12 % of the transgenic plants showed significantly high resistance to S. exigua. Significant mortality (62 %) of H. armigera was recorded within 24 h of bioassays. Both toxins showed synergistic effect in tobacco and broadened the spectrum of plant activity against insects.
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Affiliation(s)
- Muhammad Nouman Sohail
- Plant Molecular Biology and Transformation Laboratory, Agricultural Biotechnology Division, National Institute for Biotechnology and Genetic Engineering, Jhang Road, P.O. Box 577, Faisalabad, Pakistan
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Downes S, Mahon R. Evolution, ecology and management of resistance in Helicoverpa spp. to Bt cotton in Australia. J Invertebr Pathol 2012; 110:281-6. [DOI: 10.1016/j.jip.2012.04.005] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Mahon RJ, Downes SJ, James B. Vip3A resistance alleles exist at high levels in Australian targets before release of cotton expressing this toxin. PLoS One 2012; 7:e39192. [PMID: 22761737 PMCID: PMC3382218 DOI: 10.1371/journal.pone.0039192] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2012] [Accepted: 05/16/2012] [Indexed: 12/05/2022] Open
Abstract
Crops engineered to produce insecticidal crystal (Cry) proteins from the soil bacterium Bacillus thuringiensis (Bt) have revolutionised pest control in agriculture. However field-level resistance to Bt has developed in some targets. Utilising novel vegetative insecticidal proteins (Vips), also derived from Bt but genetically distinct from Cry toxins, is a possible solution that biotechnical companies intend to employ. Using data collected over two seasons we determined that, before deployment of Vip-expressing plants in Australia, resistance alleles exist in key targets as polymorphisms at frequencies of 0.027 (n = 273 lines, 95% CI = 0.019–0.038) in H. armigera and 0.008 (n = 248 lines, 0.004–0.015) in H. punctigera. These frequencies are above mutation rates normally encountered. Homozygous resistant neonates survived doses of Vip3A higher than those estimated in field-grown plants. Fortunately the resistance is largely, if not completely, recessive and does not confer resistance to the Bt toxins Cry1Ac or Cry2Ab already deployed in cotton crops. These later characteristics are favourable for resistance management; however the robustness of Vip3A inclusive varieties will depend on resistance frequencies to the Cry toxins when it is released (anticipated 2016) and the efficacy of Vip3A throughout the season. It is appropriate to pre-emptively screen key targets of Bt crops elsewhere, especially those such as H. zea in the USA, which is not only closely related to H. armigera but also will be exposed to Vip in several varieties of cotton and corn.
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Affiliation(s)
- Rod J Mahon
- Ecosystem Sciences Division, The Commonwealth Scientific and Industrial Research Organisation, Black Mountain Laboratories, Canberra, Australian Capital Territory, Australia.
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Multimodal protein constructs for herbivore insect control. Toxins (Basel) 2012; 4:455-75. [PMID: 22822457 PMCID: PMC3398420 DOI: 10.3390/toxins4060455] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2012] [Revised: 06/01/2012] [Accepted: 06/05/2012] [Indexed: 01/09/2023] Open
Abstract
Transgenic plants expressing combinations of microbial or plant pesticidal proteins represent a promising tool for the efficient, durable control of herbivorous insects. In this review we describe current strategies devised for the heterologous co-expression of pesticidal proteins in planta, some of which have already shown usefulness in plant protection. Emphasis is placed on protein engineering strategies involving the insertion of single DNA constructs within the host plant genome. Multimodal fusion proteins integrating complementary pesticidal functions along a unique polypeptide are first considered, taking into account the structural constraints associated with protein or protein domain grafting to biologically active proteins. Strategies that allow for the co- or post-translational release of two or more pesticidal proteins are then considered, including polyprotein precursors releasing free proteins upon proteolytic cleavage, and multicistronic transcripts for the parallel translation of single protein-encoding mRNA sequences.
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Tabashnik BE, Gould F. Delaying corn rootworm resistance to Bt corn. JOURNAL OF ECONOMIC ENTOMOLOGY 2012; 105:767-76. [PMID: 22812111 DOI: 10.1603/ec12080] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Transgenic crops producing Bacillus thuringiensis (Bt) toxins for insect control have been successful, but their efficacy is reduced when pests evolve resistance. To delay pest resistance to Bt crops, the U.S. Environmental Protection Agency (EPA) has required refuges of host plants that do not produce Bt toxins to promote survival of susceptible pests. Such refuges are expected to be most effective if the Bt plants deliver a dose of toxin high enough to kill nearly all hybrid progeny produced by matings between resistant and susceptible pests. In 2003, the EPA first registered corn, Zea mays L., producing a Bt toxin (Cry3Bb1) that kills western corn rootworm, Diabrotica virgifera virgifera LeConte, one of the most economically important crop pests in the United States. The EPA requires minimum refuges of 20% for Cry3Bb1 corn and 5% for corn producing two Bt toxins active against corn rootworms. We conclude that the current refuge requirements are not adequate, because Bt corn hybrids active against corn rootworms do not meet the high-dose standard, and western corn rootworm has rapidly evolved resistance to Cry3Bb1 corn in the laboratory, greenhouse, and field. Accordingly, we recommend increasing the minimum refuge for Bt corn targeting corn rootworms to 50% for plants producing one toxin active against these pests and to 20% for plants producing two toxins active against these pests. Increasing the minimum refuge percentage can help to delay pest resistance, encourage integrated pest management, and promote more sustainable crop protection.
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Affiliation(s)
- Bruce E Tabashnik
- Department of Entomology, University of Arizona, Tucson, AZ 85721, USA.
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Huang F, Ghimire MN, Leonard BR, Wang J, Daves C, Levy R, Cook D, Head GP, Yang Y, Temple J, Ferguson R. F2 screening for resistance to pyramided Bacillus thuringiensis maize in Louisiana and Mississippi populations of Diatraea saccharalis (Lepidoptera: Crambidae). PEST MANAGEMENT SCIENCE 2011; 67:1269-1276. [PMID: 21538799 DOI: 10.1002/ps.2182] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2010] [Revised: 03/01/2011] [Accepted: 03/02/2011] [Indexed: 05/30/2023]
Abstract
BACKGROUND In the mid-southern region of the United States, sugarcane borer, Diatraea saccharalis (F.), is a major target pest of transgenic maize expressing Bacillus thuringiensis (Bt) proteins. Novel transgenic maize technologies containing two or more pyramided Bt genes for controlling lepidopteran pests have recently become commercially available. Insect resistance management (IRM) is an important issue in the sustainable use of Bt crop technologies. The objective of this study was to determine the frequency of resistance alleles in field populations of D. saccharalis to the new pyramided Bt maize technologies. RESULTS A total of 382 F(2) family lines derived from 735 feral larvae/pupae of D. saccharalis collected from six locations in Louisiana and Mississippi during 2008 and 2009 were screened for resistance to three new Bt maize technologies: MON 89034, Genuity™ VT Triple Pro™ and SmartStax™. None of the 382 F(2) isoline families survived on the Bt maize leaf tissue for ≥ 12 days in the F(2) screen. The joint frequency for two- or three-gene resistance models with 95% probability in these populations was estimated to be < 0.0063 to MON 89034 and < 0.003 to VT Triple Pro™ and SmartStax™. CONCLUSION These results suggest that the resistance allele frequency in D. saccharalis to the three pyramided Bt maize technologies is low in the mid-southern region of the United States, which should meet the rare resistance assumption of the currently used IRM strategy for Bt maize.
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Affiliation(s)
- Fangneng Huang
- Department of Entomology, Louisiana State University Agricultural Center, Baton Rouge, LA, USA.
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Downes S, Parker TL, Mahon RJ. Characteristics of resistance to Bacillus thuringiensis toxin Cry2Ab in a strain of Helicoverpa punctigera (Lepidoptera: Noctuidae) isolated from a field population. JOURNAL OF ECONOMIC ENTOMOLOGY 2010; 103:2147-2154. [PMID: 21309238 DOI: 10.1603/ec09289] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
In 1996, the Australian cotton industry adopted Ingard that expresses the Bacillus thuringiensis (Bt) toxin gene cry1Ac and was planted at a cap of 30%. In 2004-2005, Bollgard II, which expresses cry1Ac and cry2Ab, replaced Ingard in Australia, and subsequently has made up >80% of the area planted to cotton, Gossypium hirsutum L. The Australian target species Helicoverpa armigera (Hübner) and Helicoverpa punctigera (Wallengren) are innately moderately tolerant to Bt toxins, but the absence of a history of insecticide resistance indicates that the latter species is less likely to develop resistance to Bt cotton. From 2002-2003 to 2006-2007, F2 screens were deployed to detect resistance to CrylAc or Cry2Ab in natural populations of H. punctigera. Alleles that conferred an advantage against CrylAc were not detected, but those that conferred resistance to Cry2Ab were present at a frequency of 0.0018 (n = 2,192 alleles). Importantly, the first isolation of Cry2Ab resistance in H. punctigera occurred before significant opportunities to develop resistance in response to Bollgard II. We established a colony (designated Hp4-13) consisting of homozygous resistant individuals and examined their characteristics through comparison with individuals from a Bt-susceptible laboratory colony. Through specific crosses and bioassays, we established that the resistance present in Hp4-13 is due to a single autosomal gene. The resistance is fully recessive. Homozygotes are able to survive a dose of Cry2Ab toxin that is 15 times the reported concentration in field grown Bollgard II in Australia (500 microg/ml) and are fully susceptible to Cry1Ac and to the Bt product DiPel. These characteristics are the same as those described for the first Cry2Ab resistant strain of H. armigera isolated from a field population in Australia.
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Affiliation(s)
- S Downes
- CSIRO Entomology, ACRI, Locked Bag 59, Narrabri 2390 Australia.
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Downes S, Parker T, Mahon R. Incipient resistance of Helicoverpa punctigera to the Cry2Ab Bt toxin in Bollgard II cotton. PLoS One 2010; 5:e12567. [PMID: 20830203 PMCID: PMC2935350 DOI: 10.1371/journal.pone.0012567] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2010] [Accepted: 07/01/2010] [Indexed: 11/19/2022] Open
Abstract
Combinations of dissimilar insecticidal proteins (“pyramids”) within transgenic plants are predicted to delay the evolution of pest resistance for significantly longer than crops expressing a single transgene. Field-evolved resistance to Bacillus thuringiensis (Bt) transgenic crops has been reported for first generation, single-toxin varieties and the Cry1 class of proteins. Our five year data set shows a significant exponential increase in the frequency of alleles conferring Cry2Ab resistance in Australian field populations of Helicoverpa punctigera since the adoption of a second generation, two-toxin Bt cotton expressing this insecticidal protein. Furthermore, the frequency of cry2Ab resistance alleles in populations from cropping areas is 8-fold higher than that found for populations from non-cropping regions. This report of field evolved resistance to a protein in a dual-toxin Bt-crop has precisely fulfilled the intended function of monitoring for resistance; namely, to provide an early warning of increases in frequencies that may lead to potential failures of the transgenic technology. Furthermore, it demonstrates that pyramids are not ‘bullet proof’ and that rapid evolution to Bt toxins in the Cry2 class is possible.
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Downes S, Mahon RJ, Rossiter L, Kauter G, Leven T, Fitt G, Baker G. Adaptive management of pest resistance by Helicoverpa species (Noctuidae) in Australia to the Cry2Ab Bt toxin in Bollgard II® cotton. Evol Appl 2010; 3:574-84. [PMID: 25567948 PMCID: PMC3352500 DOI: 10.1111/j.1752-4571.2010.00146.x] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2010] [Accepted: 06/08/2010] [Indexed: 11/27/2022] Open
Abstract
In Australia, monitoring Helicoverpa species for resistance to the Cry2Ab toxin in second generation Bacillus thuringiensis (Bt) cotton has precisely fulfilled its intended function: to warn of increases in resistance frequencies that may lead to field failures of the technology. Prior to the widespread adoption of two-gene Bt cotton, the frequency of Cry2Ab resistance alleles was at least 0.001 in H. armigera and H. punctigera. In the 5 years hence, there has been a significant and apparently exponential increase in the frequency of alleles conferring Cry2Ab resistance in field populations of H. punctigera. Herein we review the history of deploying and managing resistance to Bt cotton in Australia, outline the characteristics of the isolated resistance that likely impact on resistance evolution, and use a simple model to predict likely imminent resistance frequencies. We then discuss potential strategies to mitigate further increases in resistance frequencies, until the release of a third generation product. These include mandating larger structured refuges, applying insecticide to crops late in the season, and restricting the area of Bollgard II® cotton. The area planted to Bt-crops is anticipated to continue to rise worldwide; therefore the strategies being considered in Australia are likely to relate to other situations.
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Affiliation(s)
- Sharon Downes
- CSIRO Entomology, Australian Cotton Research Institute Narrabri, NSW, Australia
| | | | - Louise Rossiter
- Industry and Investment NSW, Australian Cotton Research Institute Narrabri, NSW, Australia
| | - Greg Kauter
- Cotton Australia Limited Mascot, NSW, Australia
| | - Tracey Leven
- Cotton Research and Development Corporation Narrabri, NSW, Australia
| | - Gary Fitt
- CSIRO Entomology Indooroopilly, Qld, Australia
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Mahon RJ, Young S. Selection experiments to assess fitness costs associated with Cry2Ab resistance in Helicoverpa armigera (Lepidoptera: Noctuidae). JOURNAL OF ECONOMIC ENTOMOLOGY 2010; 103:835-842. [PMID: 20568630 DOI: 10.1603/ec09330] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Population cage experiments were employed to detect variability in fitness among Cry2Ab resistant and Cry2Ab susceptible genotypes of Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae). In two experiments, reciprocal crosses between a Cry2Ab resistant colony (SP15) and a susceptible colony (GR) established populations where the frequency of the allele that conferred resistance was 0.5. Experimental populations were then maintained without exposure to Cry toxins. At the F2 generation and on later occasions, the pooled egg output from each population was sampled, and emerging neonate larvae were screened to monitor the frequency of the resistant allele. Resistance is recessive so homozygous resistant insects could be readily identified as they are the only genotype to survive and grow when exposed to a discriminating concentration of Cry2Ab toxin. Assuming Hardy-Weinberg equilibrium after the F1 generation, and the persistence of a 1:1 ratio of resistant and susceptible alleles, one quarter of the populations should be resistant. The populations in the first and second experiment were monitored for five and nine generations, respectively. The cumulative impact of any fitness costs associated with resistant genotypes was expected to result in a decline in the frequency of resistant homozygotes. In both experiments, there was no significant decline in resistance frequencies, and thus the Cry2Ab form of resistance does not seem to exhibit marked fitness costs under laboratory conditions.
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Affiliation(s)
- R J Mahon
- CSIRO Entomology, GPO Box 1700 Canberra, ACT 2601, Australia.
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