The following is a paper that I wrote for my population genetics class.
Corn is a large part of the diet of North Americans. Furthermore, 15 percent of the land coverage of genetically modified crops contain Bt proteins (Hoftmann 2011). Bt corn was created because there is a high demand for corn that is damage free. Corn pests include wireworms (Elateridae sp.), cutworms (Noctuidae sp.), European corn borer (Ostrinia nubilalis), corn earworm (Helicoverpa zea), and white grubs (Phyllophaga sp.). In the past, the soil had to be treated before planting in order for the plants to be unaffected. Affected plants had stunted growth which led to a reduction in their yield. Not all pre-planting treats were effective either. (University of Kentucky) In the past, in order to deal with these pests crop rotation was also used. The areas most affected by these pests were Illinois, Indiana, Michigan, Ohio, and Iowa.
Bt corn first appeared in 1996 in Zurich Switzerland. Monsanto had the corn in development since 1992. The genes cry1Ab, bar, and bla were put into the corn. The cry1Ab gene comes from Bacilus thuringiensis, bar from Streptomyces hygroscopicus, and bla from Esherichia coli. Cry1Ab makes the crop resistant to lepidopteran species (butterflies and moths) by damaging midgut lining. It breaks down the gut wall which allows bacteria to flood into the body cavity. Bar makes crops resistant to herbicides by eliminating the activity of glufosinate in cells. It does this by acetylation. Bla detoxifies beta lactam antibiotics. This paper will focus on the bar insertion that causes resentence to pests, the Bt gene. Current the crop is used for food in 13 countries, feed in 10, and cultivation in 4 (International Service for the acqaution of agro-biotech applications.) Currently, Monsanto is working on increasing the resistance with corn rootworms (Diabrotica virgifera) and pink bollworms (Pectinophora gossypiella) (Monsanto 2015).
These genes were all transferred into the plant cells by microparticle bombardment. This same process has been used in canola (Brassica napus), cotton (Gossypium sp.), papaya (Carica papaya), rice, soybeans (Glycine max), tomatoes (Solanum lycopersicum), and bentgrass (Agrostis sp.). The genes that you want to insert into a cell are placed on micron-sized metal particles. Then these particles are placed in a device that will accelerate them. The microparticles are then able to penetrate the cell wall of plants. This method has been used since the late 80s. (Talyor 2002)
There are four main concerns related to the Bt corn (Oberhauser 2003). The 1st is the flow of genes from the corn to other plants. This has been well documented. The 2nd concern is that the crops may produce super pests by causing the evolution of resistance. The pests only have the options of adaptations or dying. The Bt proteins may also affect the surrounding soil. Lastly, there has shown to be an effect on non-target species.
The flow of herbicide resistance from crops to weeds has been documented (Hall 2000). It is a concern that this could happen and enhance the weed like qualities that weeds have (Oberhauser 2003). Of great concern, is related to contamination of organic crops. However, studies have shown that outside 4-5 meter of a field of corn the amount of pollen statistically significantly decreases (Oberhauser 2003). 0-100 meters the range at which other studies have witnessed pollen traveling (Kuparinen 2007). Monsanto has a policy that clearly states that they have never sued/ will never sue a farmer over trace amounts of their GMO pollen being found in their field (Monsanto 2015). The reason that people can be sued over certain uses of GMOs is that they are copyrighted by the company that created them. There have been cases of farmers being sued for saving the GMO seeds, as it is a violation of their contact.
The major pest of corn in South Africa is Busseola fusca. It was revealed in 2013 that these moths were starting to develop a resistance to Bt corn. A strategy to combat this is to plant small patches of non-GMO corn in a field so that populations of insects that are susceptible to the pesticide are maintained. Resistant to the Bt proteins appears to be a dominant trait as well, so in order for a moth to have susceptibility then both parents would have to be susceptible. Other super pests appear to inherited resistance in a recessive fashion which makes them less of a threat and easily managed by planting patches of non-GMOs (Pascal 2013).
Because the Cry1Ab gene makes crops resistant to grazing from lepidopteran there was suppression that the plants would also be harmful to members of that group that were not agricultural pests. The plants do not, however, harm beetles, flies, bees, and wasps. (University of Kentucky) The corn produces crystalline toxins that regulate insect pollutions in a variety of ecosystems. Pesticides are also typically not applied to 100 percent of the plant, especially not found in the roots. They are also limited in the application when it comes to temporal scale. With the Bt modification, all parts of the plant at all times are exhibiting these pesticide qualities.
Lepidoptera provides important ecosystem services including pollination, food resources to birds and bats, and have a wide range of applications for modeling (Wood 2012). Monarchs (Danaus plexippus) and peacock butterflies (Aglaid io) have been documented to have adverse effects from exposure to the Bt proteins (Felke 2010, Stanley-Horn 2001). Exposure has been shown to decrease survival, leaf consumption, and organismal weight of organisms raised on leaves dusted with the pollen. Negative effects were also observed on black swallowtails (Papilio polyxenes). No effects were seen on milkweed tiger moths (Euchaetes egle). (Oberhauser 2003). It is general agreement among researchers that the impact of the pollen needs to be studied on other species.
There are three different ways that Bt corn could affect the soil; substances extruded by the roots, falling pollen, and resident organic material. Studies have looked at the changes in rhizobacterial communities in fields with both GMO corn and non-GMO corn over a 4 year period. That is, they looked at the types of bacteria that live on the roots of plants. This was done doing next-generation sequencing. There was no significant difference between the two fields (Barriuso 2012). The proteins have been found to be rapidly acted on by active soil particles. These proteins have had no effect on earthworms, nematodes, protozoa, bacteria, or fungi. However, they may reduce the length of mycelium. (Zhou 2011). The effects on soil still need further investigation.
Non-scientists have expressed concern that there is potential for the Bt proteins to show up in the meat of animals that are fed Bt corn. Researchers compared to groups of hens, those feed GMOs and those not fed GMOs. Metabolism and performance data was the same for the two groups. Using PCR the corn-chloroplast ivr gene was amplified. No Bt genes were found in the chickens in either organs, meat or eggs. This suggests that the Bt corn was processed normally in these chickens (Aeschbacher 2005). Other studies have also shown that there is no effect of the feed of animals on the resulting animal products in regards to GMO proteins (EFSA GMO Panel Working Group on Animal Feeding Trials 2008). These studies included sheep, pigs, chickens, cows, rodents, and fish.
While there are benefits of Bt corn, it may affect lepidopteran in significant ways. These effects can be minimized in certain ways. For example, certain areas, like the Atlantic forest, are hotspots for Lepidoptera (Brown 2000). If these areas are avoided, and crops rotated when super pests appear to be evolving then there are few issues related to Bt corn. Soil ecology is not changed, pollen does not travel that far, the proteins are not detected in the tissue of animals that were feed GMO plants with Bt proteins, and it increases crop yields. However, it needs to be concerned if the use of Bt corn in an area outweighs the negative effects on lepidopteran.
Works Cited: Aeschbacher K, Messikommer R, Meile L, Wenk C. 2005.Bt176 corn in poultry nutrition: physiological characteristics and fate of recombinant plant DNA in chickens. Poult Sci.;84(3):385-94. Barriuso J, Valverde J, Mellado R. 2012.Effect of Cry1Ab Protein on Rhizobacterial Communities of Bt-Maize over a Four-Year Cultivation Period. PLoS One; 7(4): e35481. Biosafety Scanner. 2015. EVENT BT 176 AND DETECTION METHODS. Web. http://en.biosafetyscanner.org/schedaevento.php?radioeventi=radiobutton&evento=86&evento1=#tabs-1 Brown, K., and Feitas, A. V. 2000. Atlantic Forest Butterflies: Indicators for Landscape Conservation. Biotropica, 32(4), 934-56. EFSA GMO Panel Working Group on Animal Feeding Trials. 2008. Safety and nutritional assessment of GM plants and derived food and feed: the role of animal feeding trials. Food Chem Toxicol. 46 Suppl 1:S2-70. Felke, M., Langenbrach, G. A., Feiertag, S., and Kassa, A. 2010.Effect of Bt-176 maize pollen on first instar larvae of the Peacock butterfly (Inachis io). Environmental Biosafety Research; 9(01), 5-12. International Service for the acqaution of agro-biotech applications. Event Name: Bt176 (176) https://www.isaaa.org/gmapprovaldatabase/event/default.asp?EventID=127 Kuparinen, A., Schurr, F., Tackenberg, O., and O'Hara, R. March 2007. Air-Mediated Pollen Flow from Genetically Modified to Conventional Crops. Ecological Applications, 17(2), 431-440. Monsanto. 2015. Insect Resistance to GMO Corn and Cotton Bt Crops with Insect Protection. Web. http://www.monsanto.com/newsviews/pages/insect-resistance-to-gmo-and-bt-crops.aspx Pascal Campagne, Marlene Kruger, Rémy Pasquet, Bruno Le Ru, Johnnie Van den Berg. 2013. Dominant Inheritance of Field-Evolved Resistance to Bt Corn in Busseola fusca. PLoS ONE; 8 (7) Stanley-Horn, D., Diverly, G., Hellmich, R., Mattila, H., Sears, M., Rose, R., Jesse, L., Losey, J., Obryclci, J., and Lewis, L. 2001. Assessing the impact of CrylAb- expressing corn pollen on monarch butterfly larvae in field studies. Proceedings of the national academy of sciences; 98(21) 11931-11936. Taylor NJ, Fauquet CM. 2002. Microparticle bombardment as a tool in plant science and agricultural biotechnology. DNA Cell Biol. 21(12):963-77. University of Kentucky. 2015. Bt-CORN: WHAT IT IS AND HOW IT WORKS. Web. http://www2.ca.uky.edu/entomology/entfacts/ef130.asp Wood, E., Pidgeon, A., Liu, F., and Mladenoff, D. September 15, 2012. Birds see the trees inside the forest: the potential impacts of changes in forest composition on songbirds during spring migration. Forest Ecology and Management, 280, 176-186. Zhou XY, Liu N, Zhao M, Li H, Zhou L, Tang ZW, Cao F, Li W. 2011.Advances in effects of insecticidal crystal proteins released from transgenic Bt crops on soil ecology. Yi Chuan;33(5):443-8.
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