scholarly journals Two–toxin strategies for management of insecticidal transgenic crops: can pyramiding succeed where pesticide mixtures have not?

1998 ◽  
Vol 353 (1376) ◽  
pp. 1777-1786 ◽  
Author(s):  
R. T. Roush
Keyword(s):  
At Risk ◽  
Insect Pests ◽  
Extended Period ◽  
Transgenic Crops ◽  
Cross Resistance ◽  
Bt Toxin ◽  
Pesticide Mixtures ◽  
Highly Sensitive ◽  
Evolution Of Resistance ◽  
Bt Gene

Transgenic insect–resistant crops that express toxins from Bacillus thuringiensis (Bt) offer significant advantages to pest management, but are at risk of losing these advantages to the evolution of resistance in the targeted insect pests. All commercially available cultivars of these crops carry only a single Bt gene, and are particularly at risk where the targeted insect pests are not highly sensitive to the Bt toxin used. Under such circumstances, the most prudent method of avoiding resistance is to ensure that a large proportion of the pest population develops on non–transgenic ‘refuge’ hosts, generally of the crop itself. This has generated recommendations that 20% or more of the cotton and maize in any given area should be non–transgenic. This may be costly in terms of yields and may encourage further reliance on and resistance to pesticides. The use of two or more toxins in the same variety (pyramiding) can reduce the amount of refuge required to delay resistance for an extended period. Cross–resistance among the toxins appears to have been overestimated as a potential risk to the use of pyramids (and pesticide mixtures) because cross–resistance is at least as important when toxicants are used independently. Far more critical is that there should be nearly 100% mortality of susceptible insects on the transgenic crops. The past failures of pesticide mixtures to manage resistance provide important lessons for the most efficacious deployment of multiple toxins in transgenic crops.

scholarly journals Evolution of Asian Corn Borer Resistance to Bt Toxins Used Singly or in Pairs

Toxins ◽  
2019 ◽  
Vol 11 (8) ◽  
pp. 461 ◽  
Author(s):  
Yueqin Wang ◽  
Yudong Quan ◽  
Jing Yang ◽  
Changlong Shu ◽  
Zhenying Wang ◽  
...  
Keyword(s):  
Transgenic Crops ◽  
Model System ◽  
Cross Resistance ◽  
Ostrinia Furnacalis ◽  
Worst Case ◽  
Corn Borer ◽  
Laboratory Selection ◽  
Bt Toxins ◽  
Asian Corn Borer ◽  
Evolution Of Resistance

Transgenic crops producing insecticidal proteins from Bacillus thuringiensis (Bt) have revolutionized pest control, but the benefits of this approach have been reduced by the evolution of resistance in pests. The widely adopted ’pyramid strategy’ for delaying resistance entails transgenic crops producing two or more distinct toxins that kill the same pest. The limited experimental evidence supporting this strategy comes primarily from a model system under ideal conditions. Here we tested the pyramid strategy under nearly worst-case conditions, including some cross-resistance between the toxins in the pyramid. In a laboratory selection experiment with an artificial diet, we used Bt toxins Cry1Ab, Cry1F, and Cry1Ie singly or in pairs against Ostrinia furnacalis, one of the most destructive pests of corn in Asia. Under the conditions evaluated, pairs of toxins did not consistently delay the evolution of resistance relative to single toxins.

scholarly journals Pink Bollworm Resistance to Bt Toxin Cry1Ac Associated with an Insertion in Cadherin Exon 20

Toxins ◽  
2019 ◽  
Vol 11 (4) ◽  
pp. 186 ◽  
Author(s):  
Ling Wang ◽  
Yuemin Ma ◽  
Xueqin Guo ◽  
Peng Wan ◽  
Kaiyu Liu ◽  
...  
Keyword(s):  
Insect Pests ◽  
Stop Codon ◽  
Premature Stop Codon ◽  
Pink Bollworm ◽  
Cross Resistance ◽  
Bt Cotton ◽  
Wild Type ◽  
Bt Toxin ◽  
Exon 20 ◽  
In Cells

Insecticidal proteins from Bacillus thuringiensis (Bt) are widely used to control insect pests, but their efficacy is reduced when pests evolve resistance. We report on a novel allele (r16) of the cadherin gene (PgCad1) in pink bollworm (Pectinophora gossypiella) associated with resistance to Bt toxin Cry1Ac, which is produced by transgenic cotton. The r16 allele isolated from a field population in China has 1545 base pairs of a degenerate transposon inserted in exon 20 of PgCad1, which generates a mis-spliced transcript containing a premature stop codon. A strain homozygous for r16 had 300-fold resistance to Cry1Ac, 2.6-fold cross-resistance to Cry2Ab, and completed its life cycle on transgenic Bt cotton producing Cry1Ac. Inheritance of Cry1Ac resistance was recessive and tightly linked with r16. Compared with transfected insect cells expressing wild-type PgCad1, cells expressing r16 were less susceptible to Cry1Ac. Recombinant cadherin protein was transported to the cell membrane in cells transfected with the wild-type PgCad1 allele, but not in cells transfected with r16. Cadherin occurred on brush border membrane vesicles (BBMVs) in the midgut of susceptible larvae, but not resistant larvae. These results imply that the r16 allele mediates Cry1Ac resistance in pink bollworm by interfering with the localization of cadherin.

scholarly journals Cadherin repeat 5 mutation associated with Bt resistance in a field-derived strain of pink bollworm

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Ling Wang ◽  
Yuemin Ma ◽  
Wei Wei ◽  
Peng Wan ◽  
Kaiyu Liu ◽  
...  
Keyword(s):  
Brush Border Membrane ◽  
Insect Cells ◽  
Transcript Abundance ◽  
Pink Bollworm ◽  
Cross Resistance ◽  
Bt Cotton ◽  
Wild Type ◽  
Bt Toxin ◽  
Bt Resistance ◽  
Evolution Of Resistance

Abstract Evolution of resistance by pests reduces the benefits of transgenic crops that produce insecticidal proteins from Bacillus thuringiensis (Bt). Here we analyzed resistance to Bt toxin Cry1Ac in a field-derived strain of pink bollworm (Pectinophora gossypiella), a global pest of cotton. We discovered that the r14 allele of the pink bollworm cadherin gene (PgCad1) has a 234-bp insertion in exon 12 encoding a mutant PgCad1 protein that lacks 36 amino acids in cadherin repeat 5 (CR5). A strain homozygous for this allele had 237-fold resistance to Cry1Ac, 1.8-fold cross-resistance to Cry2Ab, and developed from neonate to adult on Bt cotton producing Cry1Ac. Inheritance of resistance to Cry1Ac was recessive and tightly linked with r14. PgCad1 transcript abundance in midgut tissues did not differ between resistant and susceptible larvae. Toxicity of Cry1Ac to transformed insect cells was lower for cells expressing r14 than for cells expressing wild-type PgCad1. Wild-type PgCad1 was transported to the cell membrane, whereas PgCad1 produced by r14 was not. In larval midgut tissue, PgCad1 protein occurred primarily on the brush border membrane only in susceptible larvae. The results imply r14 mediates pink bollworm resistance to Cry1Ac by reduced translation, increased degradation, and/or mislocalization of cadherin.

scholarly journals Evaluating Cross-Resistance to Cry and Vip Toxins in Four Strains of Helicoverpa armigera With Different Genetic Mechanisms of Resistance to Bt Toxin Cry1Ac

2021 ◽  
Vol 12 ◽  
Author(s):  
Liangxuan Qi ◽  
Hanyang Dai ◽  
Zeng Jin ◽  
Huiwen Shen ◽  
Fang Guan ◽  
...  
Keyword(s):  
Helicoverpa Armigera ◽  
Genetic Basis ◽  
Cross Resistance ◽  
Bt Cotton ◽  
Bt Toxin ◽  
Field Control ◽  
Helicoverpa Armígera ◽  
Genetic Mechanisms ◽  
Evolution Of Resistance ◽  
Control Failures

Evolution of resistance by pests has diminished the efficacy of transgenic crops producing insecticidal proteins from Bacillus thuringiensis (Bt). In China, where transgenic cotton producing Bt toxin Cry1Ac has been planted since 1997, field control failures have not been reported but the frequency of resistance to Cry1Ac has increased in the cotton bollworm, Helicoverpa armigera. This provides incentive to switch to multi-toxin Bt cotton, which is grown in many other countries. Previous work created four laboratory strains of H. armigera with >100-fold resistance to Cry1Ac, with the genetic basis of resistance known in all but the LF256 strain. Here, we analyzed the genetic basis of resistance in Cry1Ac in LF256 and evaluated cross-resistance of all four strains to three toxins produced by widely planted multi-toxin Bt cotton: Cry1Fa, Cry2Ab, and Vip3Aa. DNA sequencing revealed that LF256 lacked the mutations in three genes (HaTSPAN1, HaABCC2, and HaABCC3) that confer resistance to Cry1Ac in two other strains of H. armigera we analyzed. Together with previous results, the data reported here show that each of the four strains examined has a different genetic basis of resistance to Cry1Ac. Significant positive cross-resistance occurred to Cry1Fa in three of the four strains tested but not to Cry2Ab or Vip3Aa in any strain. Thus, Cry2Ab and Vip3Aa are likely to be especially valuable for increasing the efficacy and durability of Bt cotton against H. armigera populations that have some resistance to Cry1Ac.

scholarly journals Cryo-EM structures of an insecticidal Bt toxin reveal its mechanism of action on the membrane

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Matthew J. Byrne ◽  
Matthew G. Iadanza ◽  
Marcos Arribas Perez ◽  
Daniel P. Maskell ◽  
Rachel M. George ◽  
...  
Keyword(s):  
Functional Data ◽  
Insect Pests ◽  
Economic Cost ◽  
Commercial Agriculture ◽  
Efficient Manner ◽  
Bt Toxin ◽  
Genes Encoding ◽  
Potential Applications ◽  
Chemical Pesticides ◽  
Wide Potential

AbstractInsect pests are a major cause of crop losses worldwide, with an estimated economic cost of $470 billion annually. Biotechnological tools have been introduced to control such insects without the need for chemical pesticides; for instance, the development of transgenic plants harbouring genes encoding insecticidal proteins. The Vip3 (vegetative insecticidal protein 3) family proteins from Bacillus thuringiensis convey toxicity to species within the Lepidoptera, and have wide potential applications in commercial agriculture. Vip3 proteins are proposed to exert their insecticidal activity through pore formation, though to date there is no mechanistic description of how this occurs on the membrane. Here we present cryo-EM structures of a Vip3 family toxin in both inactive and activated forms in conjunction with structural and functional data on toxin–membrane interactions. Together these data demonstrate that activated Vip3Bc1 complex is able to insert into membranes in a highly efficient manner, indicating that receptor binding is the likely driver of Vip3 specificity.

Ready Player Two: A randomised controlled pilot trial investigating the feasibility of using games to improve healthy lifestyle knowledge in youth (9-16 years) at risk for type two diabetes. (Preprint)

2021 ◽  
Author(s):  
Ralph Maddison ◽  
Nilufar Baghaei ◽  
Amanda Jane Calder ◽  
Rinki Murphy ◽  
Varsha Parag ◽  
...  
Keyword(s):  
At Risk ◽  
New Zealand ◽  
Healthy Lifestyle ◽  
Pilot Trial ◽  
Extended Period ◽  
Trial Registration ◽  
Diabetes Knowledge ◽  
Game Play ◽  
Health Research Council ◽  
Randomised Controlled

UNSTRUCTURED Objective: To determine the comparative use and knowledge effects of two prototype serious games for health on healthy lifestyle knowledge in youth aged 9-16 years at risk for type 2 diabetes (T2D). Methods: A three-arm parallel randomized controlled pilot trial was undertaken to assess use of the game, and the effect of the game on healthy lifestyle and T2D diabetes knowledge. Participants were allocated to ‘Diabetic Jumper’ (n=7), ‘Ari and Friends’ (n=8), or a control game (n=8). All participants completed healthy lifestyle and T2D knowledge questionnaires at baseline, immediately after game play, and four weeks after game play. Game attitudes and preferences were also assessed. The primary outcome was the use of the game, specifically, the number of minutes played over four weeks. Results: There were no statistical differences in healthy lifestyle knowledge or diabetes knowledge over time or across games. Only one participant accessed the game for an extended period, playing the game for a total of 33 min over 4 weeks. Conclusion: Two prototype serious were unsuccessful at sustaining long-term play outside a clinic environment. However, the potential for these games to be used as stimulus to engage young people with healthy lifestyle and diabetes knowledge in a clinic setting should be further explored. Suggested improvements for future studies are discussed. Trial Registration: Australia New Zealand Clinical Trials Registry, ACTRN12619000380190. Registered 11 March 2019, https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=377123 Funding: The trial was funded by a Health Research Council of New Zealand Feasibility grant.

scholarly journals Genetically Modified Potato for Pest Resistance: Thrift or Threat?

2021 ◽  
Author(s):  
Martin Raspor ◽  
Aleksandar Cingel
Keyword(s):  
Insect Pests ◽  
Genetically Modified ◽  
New Technology ◽  
Single Gene ◽  
Genetically Modified Crops ◽  
Pest Resistance ◽  
Potato Production ◽  
Bt Toxin ◽  
Long Term Impact ◽  
The Cost

Significant limitations in potato production are crop loss due to the damage made by insect pests, and the cost of enormous amount of chemicals, harmful to humans and environment, extensively used in their control. As an alternative, development of genetically modified potato offered possibility for pest management in a more sustainable, environmentally friendly way. Over the past 30 years introduction of pest resistance traits progressed from a single gene to multiple stacked events and from Bt-toxin expression to expression of proteins from non-Bt sources, dsRNA and their combination, while advances in molecular biology have brought “cleaner” gene manipulation technologies. However, together with benefits any new technology also bears its risks, and there are still a range of unanswered questions and concerns about long-term impact of genetically modified crops – that with knowledge and precautionary approaches can be avoided or mitigated. Sustainability of genetically modified crops for pest control largely depends on the willingness to gain and implement such knowledge.

scholarly journals Hybridizing transgenic Bt cotton with non-Bt cotton counters resistance in pink bollworm

2017 ◽  
Vol 114 (21) ◽  
pp. 5413-5418 ◽  
Author(s):  
Peng Wan ◽  
Dong Xu ◽  
Shengbo Cong ◽  
Yuying Jiang ◽  
Yunxin Huang ◽  
...  
Keyword(s):  
First Generation ◽  
Resistance Management ◽  
Genetically Engineered ◽  
Pink Bollworm ◽  
Bt Cotton ◽  
Bt Toxin ◽  
Random Mixture ◽  
Cotton Plants ◽  
Evolution Of Resistance ◽  
Insecticide Sprays

Extensive cultivation of crops genetically engineered to produce insecticidal proteins from the bacteriumBacillus thuringiensis(Bt) has suppressed some major pests, reduced insecticide sprays, enhanced pest control by natural enemies, and increased grower profits. However, these benefits are being eroded by evolution of resistance in pests. We report a strategy for combating resistance by crossing transgenic Bt plants with conventional non-Bt plants and then crossing the resulting first-generation (F1) hybrid progeny and sowing the second-generation (F2) seeds. This strategy yields a random mixture within fields of three-quarters of plants that produce Bt toxin and one-quarter that does not. We hypothesized that the non-Bt plants in this mixture promote survival of susceptible insects, thereby delaying evolution of resistance. To test this hypothesis, we compared predictions from computer modeling with data monitoring pink bollworm (Pectinophora gossypiella) resistance to Bt toxin Cry1Ac produced by transgenic cotton in an 11-y study at 17 field sites in six provinces of China. The frequency of resistant individuals in the field increased before this strategy was widely deployed and then declined after its widespread adoption boosted the percentage of non-Bt cotton plants in the region. The correspondence between the predicted and observed outcomes implies that this strategy countered evolution of resistance. Despite the increased percentage of non-Bt cotton, suppression of pink bollworm was sustained. Unlike other resistance management tactics that require regulatory intervention, growers adopted this strategy voluntarily, apparently because of advantages that may include better performance as well as lower costs for seeds and insecticides.

scholarly journals Bacillus thuringiensis Vip3Aa Toxin Resistance in Heliothis virescens (Lepidoptera: Noctuidae)

2017 ◽  
Vol 83 (9) ◽  
Author(s):  
Brian R. Pickett ◽  
Asim Gulzar ◽  
Juan Ferré ◽  
Denis J. Wright
Keyword(s):  
Bacillus Thuringiensis ◽  
Heliothis Virescens ◽  
Insect Pests ◽  
Management Strategies ◽  
Resistance Management ◽  
Cross Resistance ◽  
Inheritance Of Resistance ◽  
Resistant Parent ◽  
Bt Crops ◽  
Content Type

ABSTRACT Laboratory selection with Vip3Aa of a field-derived population of Heliothis virescens produced >2,040-fold resistance in 12 generations of selection. The Vip3Aa-selected (Vip-Sel)-resistant population showed little cross-resistance to Cry1Ab and no cross-resistance to Cry1Ac. Resistance was unstable after 15 generations without exposure to the toxin. F1 reciprocal crosses between Vip3Aa-unselected (Vip-Unsel) and Vip-Sel insects indicated a strong paternal influence on the inheritance of resistance. Resistance ranged from almost completely recessive (mean degree of dominance [h] = 0.04 if the resistant parent was female) to incompletely dominant (mean h = 0.53 if the resistant parent was male). Results from bioassays on the offspring from backcrosses of the F1 progeny with Vip-Sel insects indicated that resistance was due to more than one locus. The results described in this article provide useful information for the insecticide resistance management strategies designed to overcome the evolution of resistance to Vip3Aa in insect pests. IMPORTANCE Heliothis virescens is an important pest that has the ability to feed on many plant species. The extensive use of Bacillus thuringiensis (Bt) crops or spray has already led to the evolution of insect resistance in the field for some species of Lepidoptera and Coleoptera. The development of resistance in insect pests is the main threat to Bt crops. The effective resistance management strategies are very important to prolong the life of Bt plants. Lab selection is the key step to test the assumption and predictions of management strategies prior to field evaluation. Resistant insects offer useful information to determine the inheritance of resistance and the frequency of resistance alleles and to study the mechanism of resistance to insecticides.

scholarly journals Synergic Interaction between Permethrin and Bt toxins discovered using RNA-seq

2019 ◽  
Author(s):  
Takuma Sakamoto ◽  
Toshinori Kozaki ◽  
Norichika Ogata
Keyword(s):  
Differentially Expressed Gene ◽  
Model Organisms ◽  
Cross Resistance ◽  
Agricultural Pests ◽  
Bt Toxin ◽  
Development Of Resistance ◽  
Bt Toxins ◽  
Increased Susceptibility

AbstractActing against the development of resistance to antibiotics and insecticides, involving negatively correlated cross-resistance (NCR) is an alternative to use- and-discard approach. It is termed NCR that toxic chemicals interact with each other and resistance of target organisms to one chemical is sometimes associated with increased susceptibility to a second chemical when; an allele confers resistance to one toxic chemical and hyper-susceptibility to another, NCR occurs. However, only 11 toxin pairs have been revealed to cause NCR in insects. Finding novel NCRs is needed for integrated pest management. We analyzed permethrin, an insecticide, induced transcriptomes of cultured fat bodies of the silkworm Bombyx mori, a lepidopteran model insect. Differentially expressed gene analyses suggested Bacillus thuringiensis (Bt) toxin was an NCR toxin of permethrin. NCR to permethrin and Bt toxins in Thysanoplusia intermixta, the agricultural pest moth, was examined; the children of permethrin survivor T. intermixta had increased susceptibility to Bt toxin. A novel NCR toxin pair, permethrin and Bt toxin, was discovered. The screening and developmental method for negatively correlated cross-resistance toxins established in this study was effective, in vitro screening using model organisms and in vivo verification using agricultural pests.

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