scholarly journals Insect resistance management in Bacillus thuringiensis cotton by MGPS (multiple genes pyramiding and silencing)

2020 ◽  
Vol 3 (1) ◽  
Author(s):  
Muhammad Mubashar ZAFAR ◽  
Abdul RAZZAQ ◽  
Muhammad Awais FAROOQ ◽  
Abdul REHMAN ◽  
Hina FIRDOUS ◽  
...  
Keyword(s):  
Bacillus Thuringiensis ◽  
Insect Pests ◽  
Crop Protection ◽  
High Dose ◽  
Bt Cotton ◽  
Artificial Chromosomes ◽  
Cotton Pests ◽  
Multiple Genes ◽  
Bt Toxins ◽  
Evolution Of Resistance

AbstractThe introduction of Bacillus thuringiensis (Bt) cotton has reduced the burden of pests without harming the environment and human health. However, the efficacy of Bt cotton has decreased due to field-evolved resistance in insect pests over time. In this review, we have discussed various factors that facilitate the evolution of resistance in cotton pests. Currently, different strategies like pyramided cotton expressing two or more distinct Bt toxin genes, refuge strategy, releasing of sterile insects, and gene silencing by RNAi are being used to control insect pests. Pyramided cotton has shown resistance against different cotton pests. The multiple genes pyramiding and silencing (MGPS) approach has been proposed for the management of cotton pests. The genome information of cotton pests is necessary for the development of MGPS-based cotton. The expression cassettes against various essential genes involved in defense, detoxification, digestion, and development of cotton pests will successfully obtain favorable agronomic characters for crop protection and production. The MGPS involves the construction of transformable artificial chromosomes, that can express multiple distinct Bt toxins and RNAi to knockdown various essential target genes to control pests. The evolution of resistance in cotton pests will be delayed or blocked by the synergistic action of high dose of Bt toxins and RNAi as well as compliance of refuge requirement.

scholarly journals Reduced Expression of a Novel Midgut Trypsin Gene Involved in Protoxin Activation Correlates with Cry1Ac Resistance in a Laboratory-Selected Strain of Plutella xylostella (L.)

Toxins ◽  
2020 ◽  
Vol 12 (2) ◽  
pp. 76 ◽  
Author(s):  
Lijun Gong ◽  
Shi Kang ◽  
Junlei Zhou ◽  
Dan Sun ◽  
Le Guo ◽  
...  
Keyword(s):  
Plutella Xylostella ◽  
Insect Pests ◽  
Sustainable Use ◽  
High Dose ◽  
Protease Gene ◽  
Rna Seq ◽  
Down Regulation ◽  
Bt Toxins ◽  
Evolution Of Resistance

Bacillus thuringiensis (Bt) produce diverse insecticidal proteins to kill insect pests. Nevertheless, evolution of resistance to Bt toxins hampers the sustainable use of this technology. Previously, we identified down-regulation of a trypsin-like serine protease gene PxTryp_SPc1 in the midgut transcriptome and RNA-Seq data of a laboratory-selected Cry1Ac-resistant Plutella xylostella strain, SZ-R. We show here that reduced PxTryp_SPc1 expression significantly reduced caseinolytic and trypsin protease activities affecting Cry1Ac protoxin activation, thereby conferring higher resistance to Cry1Ac protoxin than activated toxin in SZ-R strain. Herein, the full-length cDNA sequence of PxTryp_SPc1 gene was cloned, and we found that it was mainly expressed in midgut tissue in all larval instars. Subsequently, we confirmed that the PxTryp_SPc1 gene was significantly decreased in SZ-R larval midgut and was further reduced when selected with high dose of Cry1Ac protoxin. Moreover, down-regulation of the PxTryp_SPc1 gene was genetically linked to resistance to Cry1Ac in the SZ-R strain. Finally, RNAi-mediated silencing of PxTryp_SPc1 gene expression decreased larval susceptibility to Cry1Ac protoxin in the susceptible DBM1Ac-S strain, supporting that low expression of PxTryp_SPc1 gene is involved in Cry1Ac resistance in P. xylostella. These findings contribute to understanding the role of midgut proteases in the mechanisms underlying insect resistance to Bt toxins.

scholarly journals Resistance of Trichoplusia ni Populations Selected by Bacillus thuringiensis Sprays to Cotton Plants Expressing Pyramided Bacillus thuringiensis Toxins Cry1Ac and Cry2Ab

2014 ◽  
Vol 81 (5) ◽  
pp. 1884-1890 ◽  
Author(s):  
Wendy Kain ◽  
Xiaozhao Song ◽  
Alida F. Janmaat ◽  
Jian-Zhou Zhao ◽  
Judith Myers ◽  
...  
Keyword(s):  
Bacillus Thuringiensis ◽  
Trichoplusia Ni ◽  
Resistance Mechanisms ◽  
Vegetable Production ◽  
Bt Cotton ◽  
Content Type ◽  
Bt Toxin ◽  
Bt Toxins ◽  
Cotton Plants ◽  
Incomplete Resistance

ABSTRACTTwo populations ofTrichoplusia nithat had developed resistance toBacillus thuringiensissprays (Bt sprays) in commercial greenhouse vegetable production were tested for resistance to Bt cotton (BollGard II) plants expressing pyramided Cry1Ac and Cry2Ab. TheT. nicolonies resistant toBacillus thuringiensisserovar kurstaki formulations were not only resistant to the Bt toxin Cry1Ac, as previously reported, but also had a high frequency of Cry2Ab-resistant alleles, exhibiting ca. 20% survival on BollGard II foliage. BollGard II-resistantT. nistrains were established by selection with BollGard II foliage to further remove Cry2Ab-sensitive alleles in theT. nipopulations. The BollGard II-resistant strains showed incomplete resistance to BollGard II, with adjusted survival values of 0.50 to 0.78 after 7 days. The resistance to the dual-toxin cotton plants was conferred by two genetically independent resistance mechanisms: one to Cry1Ac and one to Cry2Ab. The 50% lethal concentration of Cry2Ab for the resistant strain was at least 1,467-fold that for the susceptibleT. nistrain. The resistance to Cry2Ab in resistantT. niwas an autosomally inherited, incompletely recessive monogenic trait. Results from this study indicate that insect populations under selection by Bt sprays in agriculture can be resistant to multiple Bt toxins and may potentially confer resistance to multitoxin Bt crops.

scholarly journals Rapid spread of a symbiotic virus in a major crop pest following wide-scale adoption of Bt-cotton in China

2021 ◽  
Author(s):  
Yutao Xiao ◽  
Wenjing Li ◽  
Xianming Yang ◽  
Pengjun Xu ◽  
Minghui Jin ◽  
...  
Keyword(s):  
Bacillus Thuringiensis ◽  
Field Data ◽  
Insect Pests ◽  
Bt Cotton ◽  
Rna Seq ◽  
Bt Crops ◽  
Crop Pest ◽  
Rapid Spread ◽  
Wide Scale ◽  
Symbiotic Microorganism

AbstractBacillus thuringiensis (Bt) crops have been widely planted and the effects of Bt-crops on populations of the target and non-target insect pests were well studied. However, the effects of Bt-crops exposure on microorganisms that interact with crop pests haven’t previously been quantified. Here, we use laboratory and field data to show that infection of Helicoverpa armigera with a symbiotic densovirus (HaDV2) is associated with its enhanced growth and resistance to Bt-cotton. Moreover, field monitoring showed a much higher incidence of cotton bollworm infection with HaDV2 in regions cultivated with Bt-cotton than in regions without it, with the rate of densovirus infection increasing with increasing use of Bt-cotton. RNA-seq suggested resistance to both baculovirus and Cry1Ac were enhanced via the immune-related pathways. These suggest that the exposure to Bt-crops has selected for beneficial interactions between the target pest and a symbiotic microorganism that enhances its performance on Bt-crops under field conditions.

scholarly journals Modeling the Evolution of Resistance in Cotton Bollworm to Concurrently Planted Bt Cotton and Bt Maize in China

2021 ◽  
Author(s):  
Wenhui Wang ◽  
Feng Xu ◽  
Yunxin Huang ◽  
Hongqiang Feng ◽  
Peng Wan
Keyword(s):  
First Generation ◽  
Resistance Management ◽  
Northern China ◽  
Cotton Bollworm ◽  
Bt Cotton ◽  
Bt Maize ◽  
Bt Toxins ◽  
Evolution Of Resistance ◽  
The One ◽  
Lepidoptera Noctuidae

Abstract BackgroundTransgenic maize expressing toxins derived from the bacterium Bacillus thuringiensis (Bt) may be commercially planted in northern China where Bt cotton has been planted for more than two decades. While Bt maize brings additional benefits for insect control, it complicates the resistance management of cotton bollworm (CBW), Helicoverpa armigera (Lepidoptera, Noctuidae), a common target of Bt cotton and Bt maize.ResultsWe developed population genetic models to assess the risk of resistance in CBW when Bt cotton and Bt maize are planted concurrently. Model simulations showed that when natural refuges are absent, the time to resistance (TTR) is less than 10 generations in the case of one-toxin Bt cotton and one-toxin Bt maize, but is more than 30 generations in the case of two-toxin Bt cotton and two-toxin Bt maize. The differences in the TTR between the two cases become greater as the proportion of natural refuge increases. Among the parameters we investigated, the fitness cost has a relatively smaller effect on the TTR, while the dominance of resistance and the proportion of natural refuge have a much greater effect.ConclusionsWe concluded that planting the first generation Bt cotton with Bt maize could significantly increase the risk of CBW resistance to Bt toxins as compared to planting a pyramid two-toxin Bt cotton. The strategies for reducing the risk of CBW resistance include replacing the one-toxin Bt cotton with a pyramid two-toxin Bt cotton, adopting a pyramid two-toxin Bt maize, and maintaining a sufficient proportion of natural refuges.

Ecological genetics and evolution in insect pests: Implications for lower input agriculture

1987 ◽  
Vol 2 (4) ◽  
pp. 153-159 ◽  
Author(s):  
Ellen L. Simms
Keyword(s):  
Insecticide Resistance ◽  
Insect Pests ◽  
Single Gene ◽  
Crop Protection ◽  
Ecological Genetics ◽  
Control Measures ◽  
Protection Measures ◽  
Evolution Of Virulence ◽  
Evolution Of Resistance ◽  
Insect Populations

AbstractThis paper has three goals: (1) to convince ecologists and evolutionary biologists to study the evolution in insects of the ability to overcome crop protection measures, (2) to provide insights into the kinds of data needed to develop methods for retarding the evolution of such traits, and (3) to suggest that the study of these phenomena can further our understanding of evolution. The evolution of resistance to chemical insecticides often results in higher application rates and constant development of new classes of these potentially environmentally degrading toxicants. Moreover, it is important to understand resistance phenomena related to alternative crop protection measures involving plant genetic resistance and biological insecticides so that these less environmentally damaging control measures can be maintained. Insecticide resistance evolves in insect populations in response to selection by chemical compounds. Similarly, selection by host-plant defenses of resistant crops leads to the evolution of virulence to those varieties. The evolution of these traits constitutes an important subject of applied evolutionary biology. In the context of single-gene evolutionary models, this article reviews the most common strategies that have been suggested for retarding the evolution of insecticide resistance. These models are also used to illustrate the effects of ecological factors and genetical properties of insect populations on the evolution of resistance. Where appropriate, the relevance of these models to the evolution of virulence to resistant crop varieties is also described. Durability in the insecticidal effectiveness of a plant protective chemical is not incompatible with the requirement for health safety in the same material.

Mechanisms of Resistance to Insecticidal Proteins from Bacillus thuringiensis

2021 ◽  
Vol 66 (1) ◽  
pp. 121-140
Author(s):  
Juan Luis Jurat-Fuentes ◽  
David G. Heckel ◽  
Juan Ferré
Keyword(s):  
Bacillus Thuringiensis ◽  
Current Knowledge ◽  
Mechanisms Of Resistance ◽  
Insecticidal Proteins ◽  
Bt Toxins ◽  
Evolution Of Resistance ◽  
Synthetic Pesticides ◽  
Bacterium Bacillus ◽  
High Level ◽  
Level Resistance

Insecticidal proteins from the bacterium Bacillus thuringiensis ( Bt) are used in sprayable formulations or produced in transgenic crops as the most successful alternatives to synthetic pesticides. The most relevant threat to sustainability of Bt insecticidal proteins (toxins) is the evolution of resistance in target pests. To date, high-level resistance to Bt sprays has been limited to one species in the field and another in commercial greenhouses. In contrast, there are currently seven lepidopteran and one coleopteran species that have evolved practical resistance to transgenic plants producing insecticidal Bt proteins. In this article, we present a review of the current knowledge on mechanisms of resistance to Bt toxins, with emphasis on key resistance genes and field-evolved resistance, to support improvement of Bt technology and its sustainability.

scholarly journals Independent and Synergistic Effects of Knocking out Two ABC Transporter Genes on Resistance to Bacillus thuringiensis Toxins Cry1Ac and Cry1Fa in Diamondback Moth

Toxins ◽  
2020 ◽  
Vol 13 (1) ◽  
pp. 9
Author(s):  
Shan Zhao ◽  
Dong Jiang ◽  
Falong Wang ◽  
Yihua Yang ◽  
Bruce E. Tabashnik ◽  
...  
Keyword(s):  
Bacillus Thuringiensis ◽  
Abc Transporter ◽  
Insect Pests ◽  
Synergistic Effects ◽  
Diamondback Moth ◽  
Cross Resistance ◽  
Vegetable Crops ◽  
Double Knockout ◽  
Bt Toxins ◽  
Abc Transporter Genes

Insecticidal proteins from Bacillus thuringiensis (Bt) are used widely in sprays and transgenic crops to control insect pests. However, evolution of resistance by pests can reduce the efficacy of Bt toxins. Here we analyzed resistance to Bt toxins Cry1Ac and Cry1Fa in the diamondback moth (Plutella xylostella), one of the world’s most destructive pests of vegetable crops. We used CRISPR/Cas9 gene editing to create strains with knockouts of the ATP-binding cassette (ABC) transporter genes PxABCC2, PxABCC3, or both. Bioassay results show that knocking out either gene alone caused at most 2.9-fold resistance but knocking out both caused >10,320-fold resistance to Cry1Ac and 380-fold resistance to Cry1Fa. Cry1Ac resistance in the double knockout strain was recessive and genetically linked with the PxABCC2/PxABCC3 loci. The results provide insight into the mechanism of cross-resistance to Cry1Fa in diamondback moth. They also confirm previous work with this pest showing that mutations disrupting both genes cause higher resistance to Cry1Ac than mutations affecting either PxABCC2 or PxABCC3 alone. Together with previous work, the results here highlight the value of using single and multiple gene knockouts to better understand the independent and synergistic effects of putative Bt toxin receptors on resistance to Bt toxins.

scholarly journals β-carotene and Bacillus thuringiensis insecticidal protein differentially modulate feeding behaviour, mortality and physiology of European corn borer (Ostrinia nubilalis)

PLoS ONE ◽  
2021 ◽  
Vol 16 (2) ◽  
pp. e0246696
Author(s):  
Patricia Sarai Girón-Calva ◽  
Carmen Lopez ◽  
Alfonso Albacete ◽  
Ramon Albajes ◽  
Paul Christou ◽  
...  
Keyword(s):  
Bacillus Thuringiensis ◽  
Ostrinia Nubilalis ◽  
Feeding Behaviour ◽  
European Corn Borer ◽  
Insect Pests ◽  
Crop Protection ◽  
Insecticidal Protein ◽  
Pupal Weight ◽  
Bt Protein ◽  
Β Carotene

Maize with enhanced β-carotene production was engineered to counteract pervasive vitamin A deficiency in developing countries. Second-generation biofortified crops are being developed with additional traits that confer pest resistance. These include crops that can produce Bacillus thuringiensis Berliner (Bt) insecticidal proteins. Currently, it is unknown whether β-carotene can confer fitness benefits through to insect pests, specifically through altering Ostrinia nubilalis foraging behaviour or development in the presence of Bt insecticidal toxin. Therefore the effects of dietary β-carotene plus Bt insecticidal protein on feeding behaviour, mortality, and physiology in early and late instars of O. nubilalis larvae were investigated. The results of two-choice experiments showed that irrespective of β-carotene presence, at day five 68%-90% of neonates and 69%-77% of fifth-instar larvae avoided diets with Cry1A protein. Over 65% of neonate larvae preferred to feed on diets with β-carotene alone compared to 39% of fifth-instar larvae. Higher mortality (65%-97%) in neonates fed diets supplemented with β-carotene alone and in combination with Bt protein was found, whereas <36% mortality was observed when fed diets without supplemented β-carotene or Bt protein. Diets with both β-carotene and Bt protein extended 25 days the larval developmental duration from neonate to fifth instar (compared to Bt diets) but did not impair larval or pupal weight. Juvenile hormone and 20-hydroxyecdysone regulate insect development and their levels were at least 3-fold higher in larvae fed diets with β-carotene for 3 days. Overall, these results suggest that the effects of β-carotene and Bt protein on O. nubilalis is dependent on larval developmental stage. This study is one of the first that provides insight on how the interaction of novel traits may modulate crop susceptibility to insect pests. This understanding will in turn inform the development of crop protection strategies with greater efficacy.

scholarly journals Demographic Performance of Helicoverpa zea Populations on Dual and Triple-Gene Bt Cotton

Toxins ◽  
2020 ◽  
Vol 12 (9) ◽  
pp. 551 ◽  
Author(s):  
Marcelo M. Rabelo ◽  
Silvana V. Paula-Moraes ◽  
Eliseu Jose G. Pereira ◽  
Blair D. Siegfried
Keyword(s):  
Population Growth ◽  
Helicoverpa Zea ◽  
Agricultural Landscape ◽  
Insect Pests ◽  
Field Resistance ◽  
Corn Earworm ◽  
Bt Cotton ◽  
Bt Toxins ◽  
Cotton Plants ◽  
Demographic Performance

Insecticidal toxins from Bacillus thuringiensis (Bt) are valuable tools for pest management worldwide, contributing to the management of human disease insect vectors and phytophagous insect pests of agriculture and forestry. Here, we report the effects of dual and triple Bt toxins expressed in transgenic cotton cultivars on the fitness and demographic performance of Helicoverpa zea (Boddie)—a noctuid pest, known as cotton bollworm and corn earworm. Life-history traits were determined for individuals of three field populations from a region where H. zea overwintering is likely. Triple-gene Bt cotton cultivars that express Cry and Vip3Aa toxins killed 100% of the larvae in all populations tested. In contrast, dual-gene Bt cotton that express Cry1Ac+Cry1F and Cry1Ac+Cry2Ab allowed population growth with the intrinsic rate of population growth (rm) 38% lower than on non-Bt cotton. The insects feeding on Bt cotton plants that express Cry1Ac+Cry2Ab, Cry1Ac+Cry1F, or Cry1Ab+Cry2Ae exhibited reduced larval weight, survival rate, and increased development time. Additionally, fitness parameters varied significantly among the insect populations, even on non-Bt cotton plants, likely because of their different genetic background and/or previous Bt toxin exposure. This is the first report of the comparative fitness of H. zea field populations on dual-gene Bt cotton after the recent reports of field resistance to certain Bt toxins. These results document the population growth rates of H. zea from an agricultural landscape with 100% Bt cotton cultivars. Our results will contribute to the development and validation of resistance management recommendations.

scholarly journals Rapid spread of a densovirus in a major crop pest following wide-scale adoption of Bt-cotton in China

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Yutao Xiao ◽  
Wenjing Li ◽  
Xianming Yang ◽  
Pengjun Xu ◽  
Minghui Jin ◽  
...  
Keyword(s):  
Bacillus Thuringiensis ◽  
Field Data ◽  
Insect Pests ◽  
Bt Cotton ◽  
Rna Seq ◽  
Bt Crops ◽  
Crop Pests ◽  
Crop Pest ◽  
Rapid Spread ◽  
Wide Scale

Bacillus thuringiensis (Bt) crops have been widely planted and the effects of Bt-crops on populations of the target and non-target insect pests have been well studied. However, the effects of Bt-crops exposure on microorganisms that interact with crop pests have not previously been quantified. Here, we use laboratory and field data to show that infection of Helicoverpa armigera with a densovirus (HaDV2) is associated with its enhanced growth and tolerance to Bt-cotton. Moreover, field monitoring showed a much higher incidence of cotton bollworm infection with HaDV2 in regions cultivated with Bt-cotton than in regions without it, with the rate of densovirus infection increasing with increasing use of Bt-cotton. RNA-seq suggested tolerance to both baculovirus and Cry1Ac were enhanced via the immune-related pathways. These findings suggest that exposure to Bt-crops has selected for beneficial interactions between the target pest and a mutualistic microorganism that enhances its performance on Bt-crops under field conditions.

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