Bacillus thuringiensis plants expressing Cry1Ac, Cry2Ab and Cry1F are not toxic to the assassin bug, Zelus renardii (original) (raw)
Related papers
Environmental Entomology, 2014
Geocoris punctipes (Say) and Orius insidiosus (Say) are generalist predators found in a wide range of crops, including cotton (Gossypium hirsutum L.) and maize (Zea mays L.), where they provide important biological control services by feeding on an array of pests, including eggs and small larvae of caterpillars. A high percentage of cotton and maize in the United States and several other countries are transgenic cultivars that produce one or more of the insecticidal Cry proteins of Bacillus thuringiensis Berliner (Bt). Here we quantify effects of three Cry proteins on the life history of these predators over two generations when they are exposed to these Cry proteins indirectly through their prey. To eliminate the confounding prey quality effects that can be introduced by Bt-susceptible prey, we used Cry1Ac/Cry2Ab-resistant Trichoplusia ni (Hü bner) and Cry1 F-resistant Spodoptera frugiperda (J.E. Smith) in a series of tri-trophic studies. Survival, development, adult mass, fecundity, and fertility were similar when predators consumed larvae feeding on Cry1Ac/Cry2Ab cotton or Cry1 F maize compared with prey feeding on isogenic or near-isogenic cotton or maize. Repeated exposure of the same initial cohort over a second generation also resulted in no differences in life-history traits when feeding on non-Bt-or Bt-fed prey. Enzyme-linked immunosorbent assay showed that predators were exposed to Bt Cry proteins from their prey and that these proteins became increasingly diluted as they moved up the food chain. Results show a clear lack of effect of three common and widespread Cry proteins on these two important predator species. The use of resistant insects to eliminate prey quality effects provides a robust and meaningful assessment of exposure and hazard. KEY WORDS transgenic Bt crop, Trichoplusia ni, Spodoptera frugiperda, biological control service, prey quality The adoption of insect-resistant transgenic crops producing the insecticidal proteins of Bacillus thuringiensis Berliner (Bt) continues to grow rapidly on a global scale. Cotton (Gossypium hirsutum L.) and maize (Zea mays L.), the two Bt crops currently under commercial production, were grown on nearly 70 million hectares in 27 countries in 2012 (James 2012). In the United States, Bt cotton and Bt maize represent Ϸ77 and 67% of total crop production, respectively (USDA-NASS 2012). These genetically engineered crops have been associated with large increases in yield and substantial reductions in insecticide use for key Lepidoptera throughout most adopting countries (Fernandez-Cornejo and Caswell 2006, Wu et al. 2008, Brookes and Barfoot 2012, Kathage and Qaim 2012). A large body of literature also has shown that the Bt proteins produced in these crops and others are selective against lepidopteran and coleopteran pests, while having little to no effect on a wide range of nontarget arthropods (Romeis et al. 2006, Marvier et al. 2007, Wolfenbarger et al. 2008, Naranjo 2009). Nonetheless, concerns about effects on nontarget organisms persist (Lö vei et al. 2009). Generalist arthropod predators represent a very important component of the biological control services in agriculture (Symondson et al. 2002). Many species are common residents in a number of agronomic and horticultural crops, where they feed on key pests and
Insect resistance to transgenic Bt crops: lessons from the laboratory and field
Journal of Economic …, 2003
Transgenic crops that produce insecticidal toxins from the bacterium Bacillus thuringiensis (Bt) grew on Ͼ62 million ha worldwide from 1996 to 2002. Despite expectations that pests would rapidly evolve resistance to such Bt crops, increases in the frequency of resistance caused by exposure to Bt crops in the Þeld have not yet been documented. In laboratory and greenhouse tests, however, at least seven resistant laboratory strains of three pests (Plutella xylostella [L.], Pectinophora gossypiella [Saunders], and Helicoverpa armigera [Hü bner]) have completed development on Bt crops. In contrast, several other laboratory strains with 70-to 10,100-fold resistance to Bt toxins in diet did not survive on Bt crops. Monitoring of Þeld populations in regions with high adoption of Bt crops has not yet detected increases in resistance frequency. Resistance monitoring examples include Ostrinia nubilalis (Hü bner) in the United States (6 yr), P. gossypiella in Arizona (5 yr), H. armigera in northern China (3 yr), and Helicoverpa zea (Boddie) in North Carolina (2 yr). Key factors delaying resistance to Bt crops are probably refuges of non-Bt host plants that enable survival of susceptible pests, low initial resistance allele frequencies, recessive inheritance of resistance to Bt crops, costs associated with resistance that reduce Þtness of resistant individuals relative to susceptible individuals on non-Bt hosts ("Þtness costs"), and disadvantages suffered by resistant strains on Bt hosts relative to their performance on non-Bt hosts ("incomplete resistance"). The relative importance of these factors varies among pest-Bt crop systems, and violations of key assumptions of the refuge strategy (low resistance allele frequency and recessive inheritance) may occur in some cases. The success of Bt crops exceeds expectations of many, but does not preclude resistance problems in the future.
Impacts of Bt crops on non-target invertebrates and insecticide use patterns
CABI Reviews, 2009
The ubiquitous nature of Bacillus thuringiensis ( Bt ), a Gram-positive bacterium capable of producing crystal proteins with insecticidal activity during sporulation, is now being mirrored in major crops plants that have been engineered through recombinant DNA to carry genes responsible for producing these crystal proteins and providing host plant resistance to major lepidopteran and coleopteran pests. In 2007, the 11th year of commercial production, Bt maize and Bt cotton were commercially produced on a total of ∼42 million hectares in 20 countries. Assessment of environmental safety has been and continues to be a key element of transgenic crop technology. This review focuses on two environmental elements, effects on non-target invertebrates and changes in insecticide use patterns since the adoption of Bt maize and cotton. Meta-analyses of the extant literature on invertebrate non-target effects reveals that the pattern and extent of impact varies in relation to taxonomy, ecologica...
Could Bt transgenic crops have nutritionally favourable effects on resistant insects?
Ecology Letters, 2003
We present an idea that larvae of some Bacillus thuringiensis (Bt ) resistant populations of the diamondback moth, Plutella xylostella (L.), may be able to use Cry1Ac toxin derived from Bt as a supplementary food protein. Bt transgenic crops could therefore have unanticipated nutritionally favourable effects, increasing the fitness of resistant populations. This idea is discussed in the context of the evolution of resistance to Bt transgenic crops.
Insecticidal activity of residual Bt protein at the second trophic level
Chinese Science Bulletin, 2006
Measurements were taken of Bt protein expressed in the leaves of transgenic cotton (Gossypium hirsutum) transformed with a synthesized Bt (Bacillus thuringiensis) cry1A gene and its persistent level in larval bodies and faeces of a non-targeted insect pest, beet armyworm (Spodoptera exigua). We performed enzyme linked immunosorbent assays (ELISA) and bioassays using neonate larvae of cotton bollworm (Helicoverpa armigera) to detect the insecticidal activity of residual Bt protein at the second trophic level. The results showed that Bt protein content in functional leaves was different at various developmental stages and was different among plants at the same stage. Even though Bt protein concentration in the larval bodies and faeces decreased 97.5%-99% compared to that found in cotton leaves subsequently fed to beet armyworm larvae, it still had a lethal effect on neonate cotton bollworm larvae. Therefore, Bt protein present at the second trophic level had insecticidal activity. This result is important in understanding and predicting the effect of transgenic plants on nontarget organisms.
An overview on resistance of insect pests against Bt Crops
2017
Bacillus thuringiensis (Bt) is a ubiquitous, rod-shaped and sporulating bacterium that produces a wide variety of insecticidal proteins active against larvae of very diverse insect orders. Once ingested by insects, these crystals are solubilized in the midgut, then proteolytically activated by midgut proteases and bound to specific receptors located in the insect cell membrane leading to cell disruption and insect death. The process of genetic transformation allows genes to be transferred from one organism/source to another, products developed through this procedure are known as genetically modified organisms (GMOs) or transgenic/biotech crops. Cry1A family is the most commonly used Bt toxins, especially Cry1Ac in transgenic Bt cotton and Cry1Ab in transgenic Bt corn. The genetically engineered insect-resistant crops (Bt crops) were first commercially grown in 1996 and adopted in different countries. The area of Bt crops planted each year continues to increase, with 181.48 million hectares grown in more than two dozen countries in 2015. The reason behind this widespread adoption of GM varieties is that it causes reduced purchases of costly inputs such as pesticide, while increases farm income along with the benefits to the environment. Genetic modification of plants has helped the agricultural system flourish; insects are beginning to evolve resistance to the Bt crops. Unfortunately, the field population of pests evolved resistance to different Bt toxins and the number of resistant species is going to increase, which is threatening to the continuous success of Bt crops. The number of resistant species has been increased worldwide, 13 cases of field-developed resistance to 5 Bt toxins in transgenic corn and cotton have been reported. Therefore, understanding of the molecular and genetic basis of resistance to Bt could help in designing a suitable management approach to delay the resistance development in the insect pests. To delay the onset of resistance, it is essential that farmers understand and implement Insect Resistance Management (IRM) practices. The tactics available for sustainable deployment of insect resistance genes in transgenic crops can be grouped into four strategies. These are not essentially mutually exclusive. Two or more strategies can be combined together by deploying one or several genes (Gene strategies), produced at high dose of the endotoxin (Dose strategies) and may be grown along with refuges, as mixtures or separate.
Bt Crops Producing Cry1Ac, Cry2Ab and Cry1F Do Not Harm the Green Lacewing, Chrysoperla rufilabris
PLoS ONE, 2013
The biological control function provided by natural enemies is regarded as a protection goal that should not be harmed by the application of any new pest management tool. Plants producing Cry proteins from the bacterium, Bacillus thuringiensis (Bt), have become a major tactic for controlling pest Lepidoptera on cotton and maize and risk assessment studies are needed to ensure they do not harm important natural enemies. However, using Cry protein susceptible hosts as prey often compromises such studies. To avoid this problem we utilized pest Lepidoptera, cabbage looper (Trichoplusia ni) and fall armyworm (Spodoptera frugiperda), that were resistant to Cry1Ac produced in Bt broccoli (T. ni), Cry1Ac/Cry2Ab produced in Bt cotton (T. ni), and Cry1F produced in Bt maize (S. frugiperda). Larvae of these species were fed Bt plants or non-Bt plants and then exposed to predaceous larvae of the green lacewing Chrysoperla rufilabris. Fitness parameters (larval survival, development time, fecundity and egg hatch) of C. rufilabris were assessed over two generations. There were no differences in any of the fitness parameters regardless if C. rufilabris consumed prey (T. ni or S. frugiperda) that had consumed Bt or non-Bt plants. Additional studies confirmed that the prey contained bioactive Cry proteins when they were consumed by the predator. These studies confirm that Cry1Ac, Cry2Ab and Cry1F do not pose a hazard to the important predator C. rufilabris. This study also demonstrates the power of using resistant hosts when assessing the risk of genetically modified plants on non-target organisms.
Proceedings of The Royal Society B: Biological Sciences, 2017
Genetically engineered (GE) crops with stacked insecticidal traits expose arthropods to multiple Cry proteins from Bacillus thuringiensis (Bt). One concern is that the different Cry proteins may interact and lead to unexpected adverse effects on non-target species. Bi-and tri-trophic experiments with SmartStax maize, herbivorous spider mites (Tetranychus urticae), aphids (Rhopalosiphum padi), predatory spiders (Phylloneta impressa), ladybeetles (Harmonia axyridis) and lacewings (Chrysoperla carnea) were conducted. Cry1A.105, Cry1F, Cry3Bb1 and Cry34Ab1 moved in a similar pattern through the arthropod food chain. By contrast, Cry2Ab2 had highest concentrations in maize leaves, but lowest in pollen, and lowest acquisition rates by herbivores and predators. While spider mites contained Cry protein concentrations exceeding the values in leaves (except Cry2Ab2), aphids contained only traces of some Cry protein. Predators contained lower concentrations than their food. Among the different predators, ladybeetle larvae showed higher concentrations than lacewing larvae and juvenile spiders. Acute effects of SmartStax maize on predator survival, development and weight were not observed. The study thus provides evidence that the different Cry proteins do not interact in a way that poses a risk to the investigated non-target species under controlled laboratory conditions.