How is bt corn created

All the other tests were performed using R for Windows, version 3. Statistical threshold was 0. The variations for all descriptors of the NTAs community structure were monitored, and patterns were almost identical in the two treatments Fig. Empty squares represent Bt corn and empty circles represent non-Bt corn.

Of all the variance in the abundance data, Tests for each sampling date indicated no difference between Bt and non-Bt corn plots. In Fig. Analysis of the distribution of species weight b k confirmed that Aphidoidea, Berytidae, Orius sauteri , Chrysopa septempunctata , Chrysoperla sinica , Harmonia axyridis , Apolygus lucorum , Araneida, Propylea japonica , Cicadella viridis , thrips, Musca domestica , Sympiezomias velatus , Chouioia cunea , Monolepta hieroglyphica , Cocconella septempunctata , Cybocephalus nipponicus , Adelphocoris fasciaticollis and Helicoverpa armigera were more abundant in Bt corn plots than in non-Bt corn plots.

In contrast, Drosophila melanogaster , Pyrgomorphidae, Pterophoridae, Laodelphax striatellus , Pleonomus canaliculatus , Trigonotylus ruficornis , Mythimna separata and Episyrphus balteata were less abundant in Bt corn plots, as compared to non-Bt corn plots. The vertical axis represents the difference in community structure between Bt filled squares and non-Bt empty circles corn plots expressed as regression coefficients Cdt of the PRC model.

The species weight b k can be regarded as the affinity of the taxon to the principal response. Only species with a weight less than Mean values of Bray-Curtis dissimilarity between Bt and non-Bt corn plots fluctuated during the study period Fig. During the whole study period, the temporal dynamics of herbivores, predators and parasitoids density showed similar trends for Bt and non-Bt corn plots.

No significant effect was observed for parasitoids density between Bt and non-Bt corn plots Fig. Three guilds were identified in Bt and non-Bt corn plots during the study period.

The results showed that the most abundant guilds in Bt and non-Bt corn plots were herbivores and predators. Parasitoids was a rare guild Fig. Of herbivores, Aphidoidea was the most abundant. Apolygus lucorum , T. Of predators, H. Chrysopa septempunctata represented the common groups Fig.

Of parasitoids, T. During the whole study period, the composition of NTAs communities was essentially uniform in Bt and non-Bt corn plots Fig. The development of GM corn producing Cry toxins significantly reduced the use of insecticides in the environment [8] , and thus may alleviate the risks of NTAs exposure to insecticides.

With the large scale planting of transgenic Bt corn, an increasing number of scientists devoted to monitoring the environmental impact of Bt corn on NTAs [58] — [60]. In this study, the potential impact of Bt corn on NTAs was monitored during a 2-yr survey to assess the environmental risks associated with Bt corn cultivation. Ecological indices such as Shannon's diversity index, Pielou's evenness index and Simpson's diversity index are useful indicators of the disturbance of NTAs community condition [61].

If the cultivation of Bt corn disrupted the biological properties, the functional indices of NTAs would be significantly lower in Bt corn as compared to non-Bt corn. However, our results indicated that the total abundance of NTAs, Shannon's diversity index, Pielou's evenness index and Simpson's diversity index showed similar values in Bt and non-Bt corn plots in most cases.

This suggested that Bt corn did not adversely affect the NTAs community structure. This finding was consistent with a previous 6-yr monitoring study showing that Bt corn did not affect NTAs community in German agricultural fields [62]. Similarly, a 2-yr study reported that environmental conditions e. It indicated that the presence of Bt toxin in the plant did not influence the population density of the assessed NTAs communities. This is consistent with previous work that found no effect of Bt corn producing Cry1Ab toxins on NTAs communities [63].

Also, community level analysis of the NTAs abundance performed in a 3-yr field study at four locations across the U. A large number of studies were conducted to assess the impact of Bt corn on NTAs. However, most of the previous studies focused on changes in NTAs abundance, resulting in the absence of data available for the dissimilarities of NTAs communities between Bt and non-Bt corn plots.

To our knowledge, this is the first time the evolution dynamics of the NTAs communities are compared between Bt and non-Bt corn plots by measuring the Bray-Curtis dissimilarity index. Here we show that dissimilarities between Bt and non-Bt corn plots were small and not significant during the study period, indicating that the presence of Cry1Ac toxins in the corn did not induce any divergence in NTAs community structure. Furthermore, our analysis revealed some changes in the structure of the NTAs community over the 2 years, but the patterns of evolution were similar in both Bt and non-Bt corn plots.

To assess potential harm of Bt corn on NTAs, representative species of corn ecosystems need to be monitored when their relevant life stages are likely to be exposed to Bt toxins in the field [65]. In this study, we calculated the density of three representative guilds herbivores, predators and parasitoids based on their different nutritional relationships, which can result in a reliable result for the differences between Bt and non-Bt corn plots. Herbivores can be exposed to Bt toxins when consuming plant materials e.

The main herbivores observed in this study were aphids, bugs, leafhoppers and thrips. Both laboratory and field studies showed that the density of these herbivores were not affected by Bt corn [62] , [67] — [72]. Our results further supported the finding that Bt corn did not affect the density of herbivores. Predators can be in contact with Bt toxins in several ways: by feeding on plant materials or pollen, by feeding on target or non-target herbivores that have ingested Bt toxins, or via the environment i.

The biological functions provided by predators or natural enemies are mandatory for a good self-regulation of insect populations in agricultural ecosystems and they should not be harmed by the use of Bt corn [74] — [76]. Consequently, the evaluation of the impact of Bt corn on natural enemies should be addressed in the ecological risk assessment. The predators recorded in this study mainly included ladybird beetles, green lacewings, Orius spp.

Their densities were not affected by Bt corn, which was in agreement with previous findings in corn fields [77] — [82].

Some laboratory tritrophic studies further confirmed that predators had no preference between Bt and non-Bt corn fed prey [75] , [83] , [84]. Unlike predators, which can feed on different prey species, parasitoids usually complete their development on a single host individual [85].

Parasitoids can attack a variety of herbivores occurring in corn ecosystems [66] , [86]. Thus, parasitoids could be affected by ingesting the Bt toxins present in host herbivores [87] , [88]. Consistent with previous observations [89] , parasitoids abundance was not adversely affected by Bt corn producing Cry1Ac toxins in our study.

A meta-analysis of 20 field studies conducted in Spain from to to assess the risks of Bt corn on NTAs confirmed that the densities of herbivores, predators and parasitoids were not affected by Bt corn, which is consistent with our results [90]. This study provides further evidence that the changes in the abundance and diversity of NTAs in corn plots are driven by time, and Cry1Ac toxin exposure only plays a negligible role, if any, in the evolution of these NTAs communities.

Interactions between corn and NTAs occur over a wide range of time scales from hours to seasons and years and are mostly driven by temperature, rainfall or sunshine. Therefore, long-term and large-scale studies taking into account a large variety of environmental parameters, including the effect of potential insecticide treatments of non Bt crops, are still required to ensure a long term efficacy of GM crops with reduced impact on the environment and agricultural ecosystems [4].

Systematically randomized plot design with Bt corn and its non-transformed near isoline Non-Bt. Analyzed the data: YYG. Browse Subject Areas? Click through the PLOS taxonomy to find articles in your field. Introduction Genetically modified GM crops have been planted for two decades since the first commercialized GM crop was released in [1]. Statistical analysis NTAs total abundances N were log x transformed prior to analysis. Results Descriptors of the NTAs communities in Bt and non-Bt corn plots The variations for all descriptors of the NTAs community structure were monitored, and patterns were almost identical in the two treatments Fig.

Download: PPT. Figure 1. Table 1. Figure 2. Bray-Curtis dissimilarity between Bt and non-Bt corn plots Mean values of Bray-Curtis dissimilarity between Bt and non-Bt corn plots fluctuated during the study period Fig.

Figure 3. Figure 4. Density changes of herbivores, predators and parasitoids in Bt and non-Bt corn plots During the whole study period, the temporal dynamics of herbivores, predators and parasitoids density showed similar trends for Bt and non-Bt corn plots.

Figure 5. Discussion The development of GM corn producing Cry toxins significantly reduced the use of insecticides in the environment [8] , and thus may alleviate the risks of NTAs exposure to insecticides.

In general there are five different steps required for using biotechnology to creates a new crop variety. These same steps are used no matter what the crop is. We will use the example of BT corn for describing each of these five steps. The soil bacterium, Bacillius thiurengensis , produces an insecticidal protein. That protein is coded for by a certain gene, one example is cry 1Ab. See how well you understand the general concepts of making a genetically engineered crop by playing this game, Who Wants to Be a Genetic Engineer?

Clicking this image will open a new window which you can make larger by clicking on and dragging the lower right-hand corner. You will not lose your place on this website page to play the game.

Figure 1 European corn borer: shotholes and tunnel in leaf midrib a , damage and fungal infection in non-Bt maize left and Bt maize b , stalk tunneling c , and adult female left and male d. All rights reserved. Figure 2 Scientist inspecting lodged maize from rootworm larvae a , maize roots from non-Bt maize hybrid right and coleopteran Bt maize hybrid b , rootworm larva white arrow feeding on maize root c , and adult western corn rootworm. There are a number of Cry toxins that are categorized by their spectrum of activity.

Maize can be genetically engineered to produce these specific Cry toxins. As such, aspects of Bt maize are similar to host plant resistance traits such as DIMBOA 2,4-dihydroxymethoxy-1,4-benzoxazinone , which at high levels reduces damage by European corn borer Klun et al. Seed providers often combine or stack traits for Lepidoptera and Coleoptera control into the same plant. Also, different types of Bt toxins targeted for the same insects are often combined into more effective plant protectants called pyramids.

This multiple toxin approach is useful for managing insect resistance to Bt maize. Successful control of insects by Bt maize has many scientists concerned that overuse of Bt maize could produce pests resistant to Bt toxins. Field-evolved resistance to Bt maize has occurred for two moth species: fall armyworm, Spodoptera frugiperda , in Puerto Rico, and African stem borer, Busseola fusca , in South Africa, so this concern is warranted.

With this strategy, insects that feed on the Bt maize are exposed to an extremely high dose of toxin; and this is complemented with refuges, usually non-Bt maize, that provide a population of susceptible insects that are not exposed to Bt toxin Figure 3. This process essentially dilutes resistance genes and maintains a population of susceptible insects.

The HDR strategy should be effective as long as plants express a high dose of the toxin, genes conferring resistance are rare, and there are many insects from the refuge available to mate randomly with resistant insects Gould Sometimes convincing growers to plant non-Bt maize refuges is a challenge because it requires careful planning of where to plant the refuge and could reduce yields.

Currently in the USA refuge recommendations range from 5—20 percent, depending on region of the country and type of Bt maize. Figure 3 Insect resistance management IRM high dose and refuge strategy assumes resistance is recessive. Many susceptible moths SS are produced in refuge maize that mate with rare resistant RR moths.

This strategy dilutes resistance genes and delays or prevents the evolution of resistance to Bt maize. Pyramided maize that produces two Bt proteins with different modes of action targeted for the same insect has reduced refuges because the two-toxin "redundant killing" reduces the chances that insects will evolve resistance. A challenge with the HDR strategy is Bt maize is not high dose for many common maize pests. For example, lepidopteran Bt maize is not high dose for fall armyworm, S. Both instances of field resistance, fall armyworm, S.

But it is unclear if resistance evolution was due to lack of high dose or insufficient refuge. Although Bt maize is an important tool for growers, it cannot completely replace other pest control tactics. Insecticides, for example, may be necessary to control secondary insect pests.

Host plant resistance is important to maintain because if pests become resistant to Bt toxins it will be needed as a backup method of pest control. Finally, Bt maize should be especially compatible with biological control because reduced use of insecticides should lead to an increase in beneficial insects Naranjo In general, traditional pest management practices must be maintained in order to avoid reliance on a single tactic.

Biological control : Control of a pest by the introduction of a natural enemy predator, parasite or pathogen. Crystal Cry proteins : Proteinacous inclusions produced by many strains of Bacillus thuringiensis during spore formation that have insecticidal activity. Cultural control : Management techniques used in agricultural to reduce pest populations, such as crop rotation. Deoxynivalenol : Mycotoxin produced by the fungus Fusarium graminearum and other fungi that occurs mainly in grains such as wheat, barley, oats and maize, also known as vomitoxin.

DIMBOA 2,4-dihydroxymethoxy-1,4-benzoxazinone : Naturally occurring compound hydroxamic acid present in maize and other related grasses that serves as a defense against insects, fungi and bacteria. European corn borer : Stem-boring insect native to Europe that was accidently introduced into North America in the first decade of the 20th century. Larval stage is a pest of grain, particularly maize. Fumonisin : Toxins produced by species of Fusarium molds that frequently occur in maize and other crops.

Certain types are harmful to humans. Genetic engineering : Insertion of a modified gene or gene from another organism using various recombinant DNA methods.

In order for the strategy to be effective the toxin dose in the plant must be sufficiently high to kill offspring derived from susceptible and resistant insects i. Host plant resistance : Natural defenses plants evolved to reduce the impact of herbivores. Plant breeders often select these traits to reduce losses due to pests. Insect resistance : Many insects have evolved resistance to insecticides, which can result in crop failures. Likewise insects can evolve resistance to GM plants.

Integrated pest management : A pest management strategy that uses a variety of methods usually biological control, host plant resistance, cultural control, and minimal use of pesticides to control crop pests. Leukoencephalomalacia : Disease of the central nervous system that affects horses, mules and donkeys, commonly called "Moldy Corn Poisoning".

Natural insecticides : An insecticide produced from plant extracts, e. Open-pollinated : Pollination occurs by natural mechanisms such as insects, birds or wind. Maize is wind pollinated. Western corn rootworm : A beetle from the family Chrysomelidae that is a major pest of maize in the United States.

The main economic damage occurs when larvae feed on maize roots that can lead to plant lodging, harvesting difficulties and yield loss.

In this beetle was discovered in Europe. Bates, S. Insect resistance management in GM crops: Past, present and future. Nature Biotechnology 23 , Brookes, G. Global impact of biotech crops: Environmental effects, AgBioForum 13 , Candolfi, M. A faunistic approach to assess potential side-effects of genetically modified Bt-corn on non-target arthropods under field conditions.

Biocontrol Science and Technology 14 , Dively, G. Effects on monarch butterfly larvae Lepidoptera: Danaidae after continuous exposure to Cry1Ab-expressing corn during anthesis. Environmental Entomology 33 , Dowd, P. Indirect reduction of ear molds and associated mycotoxins in Bacillus thuringiensis corn under controlled and open field conditions: Utility and limitations.

Journal of Economic Entomology 93 , Federici, B. Nature Biotechnology 26 , Gould, F. Sustainability of transgenic insecticidal cultivars: Integrating pest genetics and ecology. Annual Review of Entomology 43 , Hellmich, R. Romeis, A. Kennedy Springer, Monarch larvae sensitivity to Bacillus thuringiensis -purified proteins and pollen. Hutchison, W. Areawide suppression of European corn borer with Bt maize reaps savings to non-Bt maize growers. Science , James, C.

Global review of commercialized transgenic crops: Feature: Bt maize. Jesse, L. Field deposition of Bt transgenic corn pollen: Lethal effects on the monarch butterfly. Oecologia , Klun, J. Journal of Economic Entomology 60 ,