Bt crops and insect pests

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.

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

10.1101/2021.02.08.430243 ◽

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.

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An Integrative Analysis of Transcriptomics and Proteomics Reveals Novel Insights into the Response in the Midgut of Spodoptera frugiperda Larvae to Vip3Aa

Toxins ◽

10.3390/toxins14010055 ◽

2022 ◽

Vol 14 (1) ◽

pp. 55

Author(s):

Minghui Jin ◽

Yinxue Shan ◽

Yan Peng ◽

Ping Wang ◽

Qi Li ◽

...

Keyword(s):

Spodoptera Frugiperda ◽

Insect Pests ◽

Mapk Signaling ◽

Integrative Analysis ◽

Cry Proteins ◽

Apoptosis Pathway ◽

Bt Crops ◽

Hormone Synthesis ◽

Apoptosis Pathways ◽

Upregulated Genes

The insecticidal Vip3 proteins, secreted by Bacillus thuringiensis (Bt) during its vegetative growth phase, are currently used in Bt crops to control insect pests, and are genetically distinct from known insecticidal Cry proteins. Compared with Cry toxins, the mechanisms of Vip3 toxins are still poorly understood. Here, the responses of Spodoptera frugiperda larvae after Vip3Aa challenge are characterized. Using an integrative analysis of transcriptomics and proteomics, we found that Vip3Aa has enormous implications for various pathways. The downregulated genes and proteins were mainly enriched in metabolic pathways, including the insect hormone synthesis pathway, whereas the upregulated genes and proteins were mainly involved in the caspase-mediated apoptosis pathway, along with the MAPK signaling and endocytosis pathways. Moreover, we also identified some important candidate genes involved in apoptosis and MAPKs. The present study shows that exposure of S. frugiperda larvae to Vip3Aa activates apoptosis pathways, leading to cell death. The results will promote our understanding of the host response process to the Vip3Aa, and help us to better understand the mode of action of Vip3A toxins.

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CRISPR-mediated mutations in the ABC transporter gene ABCA2 confer pink bollworm resistance to Bt toxin Cry2Ab

Scientific Reports ◽

10.1038/s41598-021-89771-7 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Jeffrey A. Fabrick ◽

Dannialle M. LeRoy ◽

Lolita G. Mathew ◽

Yidong Wu ◽

Gopalan C. Unnithan ◽

...

Keyword(s):

Genetic Basis ◽

Insect Pests ◽

Pest Resistance ◽

Genetically Engineered ◽

Pink Bollworm ◽

Specific Gene ◽

Gene Encoding ◽

Bt Crops ◽

Bt Toxin ◽

First Case

AbstractCrops genetically engineered to produce insecticidal proteins from Bacillus thuringiensis (Bt) have many benefits and are important globally for managing insect pests. However, the evolution of pest resistance to Bt crops reduces their benefits. Understanding the genetic basis of such resistance is needed to better monitor, manage, and counter pest resistance to Bt crops. Previous work shows that resistance to Bt toxin Cry2Ab is associated with mutations in the gene encoding the ATP-binding cassette protein ABCA2 in lab- and field-selected populations of the pink bollworm (Pectinophora gossypiella), one of the world’s most destructive pests of cotton. Here we used CRISPR/Cas9 gene editing to test the hypothesis that mutations in the pink bollworm gene encoding ABCA2 (PgABCA2) can cause resistance to Cry2Ab. Consistent with this hypothesis, introduction of disruptive mutations in PgABCA2 in a susceptible strain of pink bollworm increased the frequency of resistance to Cry2Ab and facilitated creation of a Cry2Ab-resistant strain. All Cry2Ab-resistant individuals tested in this study had disruptive mutations in PgABCA2. Overall, we found 17 different disruptive mutations in PgABCA2 gDNA and 26 in PgABCA2 cDNA, including novel mutations corresponding precisely to single-guide (sgRNA) sites used for CRISPR/Cas9. Together with previous results, these findings provide the first case of practical resistance to Cry2Ab where evidence identifies a specific gene in which disruptive mutations can cause resistance and are associated with resistance in field-selected populations.

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Influence of elevated CO2 on development and food utilization of target armyworm Mythimna separata fed on transgenic Bt maize infected by nitrogen-fixing bacteria

10.1101/292565 ◽

2018 ◽

Author(s):

Zhuo Li ◽

Yingying Song ◽

Likun Li ◽

Long Wang ◽

Bin Liu ◽

...

Keyword(s):

Azospirillum Brasilense ◽

Insect Pests ◽

Azotobacter Chroococcum ◽

Utilization Efficiency ◽

Management Tool ◽

Food Utilization ◽

Mythimna Separata ◽

Bt Crops ◽

Mythimna Separate ◽

Buffer Control

AbstractBt crops will face a new ecological risk of reduced effectiveness against target-insect pests owing to the general decrease in exogenous-toxin content in Bt crops grown under elevated CO2. How to deal with this issue may affect the sustainability of transgenic crops as an effective pest management tool especially under future CO2 raising. In this study, azotobacters, as being one potential biological regulator to enhance crops’ nitrogen utilization efficiency, were selected and the effects of Bt maize and non-Bt maize infected by Azospirillum brasilense and Azotobacter chroococcum on development and food utilization of target Mythimna separate were studied under ambient and elevated CO2. The results indicated that azotobacter infection significantly increased larval life-span, pupal duration, RCR and AD of M. separata, and significantly decreased RGR, ECD and ECI of M. separata fed on Bt maize; There were opposite trends in development and food utilization of M. separata fed on non-Bt maize infected with azotobacters compared with the buffer control regardless of CO2 level. Presumably, the application of azotobacter infection could make Bt maize facing lower field hazards from the target pest of M. separate, and finally improve the resistance of Bt maize against target lepidoptera pests especially under elevated CO2.Summary statementElevated CO2 effect on development and food utilization of target armyworm Mythimna separata fed on Bt maize infected by azotobacter, Azospirillum brasilense and Azotobacter chroococcum

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Effects of Bt crops on non-target insect pests

Biodiversity Science ◽

10.17520/biods.2017315 ◽

2018 ◽

Vol 26 (6) ◽

pp. 636-644

Author(s):

Zhengjun Guan ◽

◽

Shunbao Lu ◽

Yanlin Huo ◽

Haoyong Hao ◽

...

Keyword(s):

Insect Pests ◽

Bt Crops

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

eLife ◽

10.7554/elife.66913 ◽

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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