GM Crops: Benefits & Concerns Pat Byrne Department of Soil & Crop Sciences
Outline Introduction Describe the current status of genetically modified (GM) crops in the US. Describe potential future applications of GM technology. Explain the methods used to produce GM plants. Discuss the risks and concerns of GM crops.
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Wide Difference Between Public and Scientists on Safety of GE Foods Generally unsafe Generally safe U.S. adults 57 37 AAAS scientists 11 88 Public and Scientists Views on Science and Society. Pew Research Center, Jan. 29, 2015
A gene is a DNA segment that encodes a specific protein that contributes to expression of a trait. mrna protein trait DNA
What are genetically engineered (GM) plants? GM indicates gene transfer using recombinant DNA technology (a set of techniques for cloning, splicing, and transferring DNA). Synonyms: Genetically engineered (GE) Transgenic Transformed
The first genetically modified crops, 10,000 years ago
Wild cabbage Many crops from one wild species: Brassica oleracea Kohlrabi Ornamental kale Kale Cabbage Cauliflower Broccoli Brussels sprouts
The rediscovery of Mendel s work in 1900 led to the era of scientific plant breeding. Hybrid corn 1930 s
The first GM plant was a tobacco plant engineered for antibiotic resistance in 1982. The first commercial release of a GM crop was the FlavrSavr tomato in 1994. The initial introduction of large-scale GM field crops was in 1996 (cotton, corn, soybeans).
Both photos: USDA Cotton bollworm Bt cotton with resistance to Lepidopterous pests has caused a major reduction in chemical insecticide use. True False
Bt Non-Bt European corn borer Source: Monsanto Western corn rootworm Widespread planting of Bt corn has led to field resistance in some target pests. True False
If pollen from a transgenic crop cross-pollinates a conventional plant, the resulting seeds will be sterile. True False
GM crops are regulated in the US by USDA EPA FDA All of the above (but not in every case)
How many different GM plant species are currently present either as fresh produce or part of a processed food product in US food markets? 1 to 10 11 to 50 51 to 100 more than 100
GM crops currently grown in the U.S. Soybeans (HT) Corn (HT, IR, DT) Cotton (HT, IR) Canola (HT) Alfalfa (HT, ID) Sugar beet (HT) Papaya (VR) Squash (VR) HT=herbicide tolerant, IR=insect resistant, VR=virus resistant, DT=drought tolerance, ID=improved digestibility
Recently approved crops Arctic non-browning apples Innate non-browning potatoes Engineered by silencing the plants polyphenol oxidase genes Innate potatoes are expected to be in U.S. stores in 2016
Percent of crop area 100 U.S. adoption of genetically engineered crops 90 80 70 60 50 40 30 20 10 Cotton Soybean Corn 0 1996 1998 2000 2002 2004 2006 2008 2010 2013 Source: USDA-ERS, 2013 93 90 90
Roundup Ready soybeans, with and without Roundup (glyphosate) treatment Photo: Monsanto Effective, flexible weed control Reduced fuel and labor costs Facilitates no-till and reduced tillage Breaks down relatively quickly; does not leach into groundwater.
However, the use of glyphosate on such large acreages raises the risk of glyphosate resistant weeds. No. of weed species that have evolved resistance to glyphosate www.weed-science.org ISB News Report, Aug. 2010, www.isb.vt.edu/news/2010/aug10.pdf
Glyphosate-resistant horseweed in Illinois Photo: Science, Sept. 20, 2013 Glyphosate-resistant kochia in eastern Colorado Photo: Phil Westra
Potential GM application: Resistance to citrus greening disease A resistance gene from spinach has been incorporated into orange trees and is currently in field tests. Effect on fruit size (NY Times) Asian citrus psyllid first appeared in Florida in 2005 (entnemdept.ufl.edu/)
Potential GM application: Biofortification of Rice and Cassava Golden Rice 2 has sufficient beta-carotene to meet 80% of the daily Vitamin A requirement Increased levels of iron, zinc, provitamin A, vitamin E, and protein Reduced levels of toxic properties Extended shelf life
Producing transgenic plants University of Nebraska-Lincoln
Inserted transgenes, like other genes, have 3 parts: Promoter Coding sequence Termination sequence Promoter controls when, where, and how much gene product is produced. Coding sequence contains information on which amino acids to include in the protein. Termination sequence marks end of gene.
Genes are inserted by two major methods Gene gun: Gold or tungsten pellets coated with DNA fragments are fired at high velocity into plant cells or tissues. Biological vector: The DNA fragment is introduced into a plasmid of Agrobacterium tumefaciens, which then transfers the genes to the plant nucleus. Plant cell
Whole plants with inserted genes are regenerated through tissue culture. Univ. of Wageningen Syngenta
New technology has made the regulatory situation fuzzier A herbicide-resistant canola created with gene-editing technology has just been released by Cibus Corp (http://www.cibus.com/) Is it a GMO or not? How will it be regulated?
Concerns with GM crops Ethical: Is GM technology playing God? Economic: Concentration of seed business in the hands of a few corporations is risky. Cross-pollination introduces GM material into organic food products. Environmental Food safety
National Research Council, National Academies Press, 2010 In general, the committee finds that genetic-engineering technology has produced substantial net environmental and economic benefits to U.S. farmers compared with non-ge crops in conventional agriculture. However, the benefits have not been universal; some may decline over time
Environmental effects of transgenic crops (from the National Research Council report) The use of pesticides with toxicity to nontarget organisms or with greater persistence in soil and waterways has typically been lower in GE fields than in non-ge, nonorganic fields. The adoption of HR crops complements conservation tillage practices, which reduces the adverse effects of tillage on soil and water quality. This may represent the largest single environmental benefit of GE crops.
Will transgenes have negative effects on nontarget organisms? Transgenic pollen harms monarch larvae, Losey et al., 1999. Nature 399:214 In a laboratory study, Monarch butterfly larvae feeding on milkweed leaves dusted with Bt corn pollen had a higher mortality than leaves dusted with non-bt corn pollen. How relevant was the lab study to the field environment?
After years of field testing, the current understanding of Bt and Monarchs is The risk of acute effects of Bt pollen to Monarchs is near zero Pollen of one type of Bt corn (Event 176) is much more toxic than other Bt corn, but accounted for < 2% of Bt acreage and is now off the market. Event 176 was much less harmful to non-target insects than spraying with chemical insecticides. The fact that event 176 cleared all the regulatory hurdles indicates that the regulatory system is not perfect.
Will pollen from GM corn cross-pollinate and reduce the value of nearby non-gm corn? West North Blue Corn South East Yellow corn = sample of 10 ears Sampling distances up to 1000 ft. Blue corn trial, Boulder County, 2002-2006
Blue corn trial, south side, 2002 2.5 ft: 46% 30 ft: 14% 150 ft: 0.53% 300 ft: 0.18% 600 ft: 0.06%
Percent cross-pollination vs. distance from pollen source, blue corn trial, Boulder Co., 2004b. 14.00 12.00 % cross-pollination 10.00 8.00 6.00 4.00 most distant blue kernels: 918 ft SW, 0.05% 150 ft: 0.07 0.42% SE SW NE NW W 2.00 0.00 0 150 300 450 600 750 900 Distance (ft)
Allergenicity of GM foods There is no evidence that an approved GM protein has produced an allergic reaction. An experimental Pioneer soybean line engineered with a Brazil nut gene to increase methionine levels provoked allergic reactions during the evaluation process. The line was immediately discontinued.
Nutritional or toxic effects There is no credible evidence that GM foods are poorer nutritionally or have more toxic effects than their conventional counterparts (U.S. National Research Council, 2004). The safety of GM food has been supported by American Medical Association World Health Organization Food and Agriculture Organization of the UN European Food Safety Authority Food Standards Australia New Zealand And many others
Some important questions regarding GM crops What is the most effective strategy to minimize the development of insect and weed resistance in response to GM crops? What is the appropriate level of regulation that protects health and the environment while rewarding innovation and improving food production? What are the best ways to ensure coexistence between GM, conventional, and organic crops? What are the most effective ways to educate consumers about agricultural and food issues?
CSU Extension Fact Sheets on GM Crops (http://extension.colostate.edu/)
References Byrne, P. 2014. Genetically Modified (GM) Crops: Techniques and Applications. CSU Extension Fact Sheet no. 0.710. Available at http://www.ext.colostate.edu/pubs/crops/00710.html Council for Agricultural Science and Technology (CAST). 2014. The potential impacts of mandatory labeling for genetically engineered food in the United States. Issue Paper 54. CAST, Ames, Iowa. Impact of Genetically Engineered Crops on Farm Sustainability in the United States. 2010. National Academies Press. Available at http://www.nap.edu/catalog/12804/impact-of-genetically-engineeredcrops-on-farm-sustainability-in-the-united-states Safety of Genetically Engineered Foods. Approaches to assessing unintended health effects. 2004. National Academies Press. Available at http://www.nap.edu/catalog/10977/safety-of-genetically-engineeredfoods-approaches-to-assessing-unintended-health
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