Failure to Yield: Evaluating the Performance of Genetically

Re: Failure to Yield: Evaluating the Performance of Genetica

Postby admin » Tue Jan 12, 2016 6:57 am


Abiotic: Descriptor of non-living environmental factors that affect the growth of crops. Abiotic stresses include drought, frost, floods, soils containing salts or heavy metals, shade, and heat.

Aggregate yield: In the context of this report, the total yield of a crop such as corn or soybeans in the United States.

Agro-ecology: The science of applying ecological principles to agriculture in order to maximize crop productivity while protecting environmental quality and sustainability. Agro-ecology typically includes organic and low-external-input production methods.

Anthropogenic: Attributable to human actions.

Biofuels: Energy sources, for transportation or other purposes, that are generated from organic matter—often, corn or other materials such as wood or grasses.

Biotechnology: Technology related to the manipulation of living organisms. Often used interchangeably with genetic engineering and genetic modification.

Bt crop: A crop variety, engineered to contain a gene from the soil bacterium Bacillus thuringiensis that produces a toxin effective against one of several insect pests, including European corn borer and corn rootworm.

Commodity crops: Crops that are eligible to receive subsidies under Title I of the federal food and farm bill. Also called row crops, they include corn, wheat, rice, soybeans, and cotton.

Confidential business information (CBI): Corporate information that is not publicly available because disclosure would be seen as compromising its economic value to the developer.

Corn rootworm: A beetle whose larvae are a major destructive pest of corn in the United States. Several species of this insect are classified under the genus Diabrotica.

Crop rotation: The alternating of different crops—a practice that typically has multiple benefits, such as the reduction of pest damage and the improvement of soil quality. The minimum rotation consists of two crops, such as the prevalent corn/soybean rotation in the U.S. Midwest. These short rotations provide fewer benefits than longer rotations.

Dead zone: An area in water bodies—notably, the Gulf of Mexico—where oxygen levels are too low to support commercially valuable fish and other sea life. Dead zones are created when high levels of nitrogen nutrients are lost from fields and enter waterways, prompting microorganism populations to spike as they consume the nutrients. After the microorganisms die, the decaying process absorbs oxygen from the water.

European corn borer (ECB): A moth (Ostrinia nubilalis) whose larvae are one of the major insect pests of corn in the United States.

Genetic engineering (GE): A technology for inserting genes or regulatory sequences from one organism into the genome of another, thereby allowing the acquired gene to be passed to progeny through reproduction. The two major categories of GE crops are those that are engineered for insect resistance (corn and cotton containing Bt genes) and herbicide tolerance (corn, cotton, canola, and soybeans containing genes that allow them to withstand herbicide applications).

Glyphosate: An herbicide that is effective against many species of weeds. Over 90 percent of all U.S. soybeans are engineered to tolerate glyphosate (a popular brand being Roundup).

Inputs: In the context of this report, substances that are needed to produce crops. Examples include fertilizers, seeds, irrigation, and pesticides.

Intrinsic yield: The highest yield, or production level, that a crop variety may achieve under ideal conditions. Also referred to as potential yield, it is distinct from operational yield.

Low-external-input (LEI): A farming method that applies agro-ecological principles of timing, crop rotation, and integrated pest management, among others, to control pests and increase production. Unlike organic farming, however, minimal use of synthetic fertilizers and pesticides is allowed.

Marker-assisted selection: A breeding method that brings several desired genes, such as those for higher yield or drought tolerance, together in a crop by tracking molecular “barcodes” (markers) associated with those traits. This method often allows faster breeding, as well as the breeding of complex traits (such as yield) that consist of several genes.

Near-isogenic (NI): Refers to plant varieties that are nearly identical to each other genetically, except for a particular gene of interest (in this report, that gene is usually either a Bt or an herbicide-tolerance gene). This property permits evaluation of the transgene’s contribution to yield or other traits.

Operational yield: Actual yield of a crop in real environments, after the damages from pests, abiotic stresses, inadequate inputs, and weather events have been taken into account. This term is distinct from intrinsic yield (which is also called potential yield).

Organic: Refers to a set of principles for cultivating crops that eschews genetically engineered crop varieties and synthetic fertilizers and pesticides. Organic operations use animal manure or legumes to supply fertilizer, often use crop rotations to foil pests, and grow cover crops to preserve and build soil quality. Organic operations contrast with conventional industrial systems.

Overall yield: Also called aggregate yield, this is the total yield of the crop—at the national level, for example—as opposed to the yield that an individual farmer may experience. The term is also distinct from the yield that may occur on a subset of the total crop (such as the yield of a particular field, measured on a per-acre basis).

Phenotype: The set of physically apparent traits in an organism, as opposed to its genotype, or set of genes. Relevant traits in the phenotype of a crop include yield, pest resistance, and drought tolerance.

Pleiotropic: Refers to the multiple effects of a gene, some of which may have agronomic or safety implications. Pleiotropic effects are common in transgenic crops because of the unpredictable interactions between the transgene or transgenic protein and the crop genome, but they may also occur in conventional crop breeding.

Potential yield: Yield of the crop when grown under ideal conditions, thereby representing the plant’s intrinsic or peak productive capacity. Also referred to as intrinsic yield, it is distinct from operational yield.

Rotation-adapted rootworm: Corn rootworms that are no longer adequately controlled by corn/soybean crop rotations. There are two recognized types—often called variant corn rootworm and extended diapause corn rootworm—but these are not usually distinguished in this report.

Stacked: Descriptor of genetically engineered crop varieties that contain more than one transgene.

Sustainable agriculture: A set of principles for cultivating crops and raising livestock that safeguards environmental quality to ensure continued productive capacity in the future.

Transgenic: Refers to organisms containing genes that have been inserted into their genetic code, usually from other organisms (transgenes), using methods that isolate the transgene from other genes of the donor organism in the laboratory.

Yield: Productivity of farmland, measured in units of harvested crop per unit of land in a specified amount of time. See also aggregate yield, intrinsic yield, operational yield, overall yield, and potential yield.

Yield drag: Yield reduction that occurs as an unintended side effect of a given trait.
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Re: Failure to Yield: Evaluating the Performance of Genetica

Postby admin » Tue Jan 12, 2016 6:58 am

Failure to Yield

Evaluating the Performance of Genetically Engineered Crops

Global events that drove food prices to record highs in 2007 and 2008 served as a reminder that humanity cannot take food production for granted. As a result, agricultural research has been refocused on the goal of producing enough food for the world’s population—by ensuring that our crops provide adequate yield. Doing so without exacerbating the harm that industrial agriculture currently imposes on the environment and society, however, will be challenging.

Genetic engineering has been promoted as an important means for dramatically improving the yields of staple food crops, but there is little evidence to support such a claim. In Failure to Yield, the Union of Concerned Scientists provides the most comprehensive evaluation to date of more than two decades of U.S. genetic engineering research and commercialization aimed at increasing crop yield. Our analysis shows that despite tremendous effort and expense, genetic engineering has only succeeded in measurably increasing the yield of one major food or livestock feed crop—and this contribution has been small compared with other available methods.

Failure to Yield also considers the substantial theoretical and practical challenges to increasing yield via genetic engineering in coming years, provides an evaluation of more promising approaches that would also minimize environmental harm, and recommends policy changes that would maximize our ability to improve crop productivity in a sustainable manner.

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Re: Failure to Yield: Evaluating the Performance of Genetica

Postby admin » Tue Jan 12, 2016 6:58 am



1 Operational and intrinsic yields cannot be distinguished in these aggregate yield numbers.

2 Insect resistance and herbicide tolerance are not included in these numbers because many of those trials include Bt and herbicide-tolerance genes that have been commercialized.

3 Virus-resistant GE papaya has prevented substantial yield loss, but it is grown only on several thousand acres in Hawaii and therefore has not contributed significantly to overall agricultural yield in the United States.

4 A more relevant measure may be the total yield of all crops produced on a unit of land over a specified period of time, which can take into account their multiple productivities. But in this report, where single crop species are considered, productivity applies only to one crop at a time.

5 Near-isogenic varieties are also called isolines or isogenic in the literature. We prefer the term near-isogenic because it makes explicit the fact that the varieties are not truly identical.

6 Some earlier studies reported yield lag—lower yield due to inferior background genetics—in some Bt varieties.

7 An extra case added artificial inoculation of first- and second-generation ECB to already high natural infestation levels. The Bt yields were 18 percent higher for this treatment. Its artificial nature and very high infestation levels, however, makes the relevance of these yield data difficult to interpret.

8 The apparent “yield boost” of 1.65 percent (Mitchell et al. 2004), independent of ECB control, is not included in our yield estimates because, as acknowledged by the authors, some or all of it may be due to factors other than Bt. For example, it may result in part from continued breeding of the Bt varieties. If included, this factor would add about a 0.55 percent yield increase to our estimates.

9 Agro-ecological principles suggest that two-crop rotations are rarely sufficient for pest control.

10 Based on USDA data (Animal and Plant Health Inspection Service 2008), 13,909 field trials were approved between 1987 and January 5, 2009, for companies, universities, and other organizations, with 2,518 of those for universities and nonprofit organizations. Thus 81.9 percent of the trials were approved for commercial entities (there are very few field trials conducted by other types of organizations).

11 HT soybeans were introduced in 1995, but they represented only a small percentage of acres that year. Five-year averages are used because they reduce the otherwise large variability of yields from year to year. However, even five-year averages are only a rough approximation of yield change, because factors that can greatly affect yield may still vary considerably between five-year periods.

12 LEI systems, like organic, attempt to achieve high production while promoting sustainability and substantial ecosystem services. Unlike organic systems, LEI allows modest input of synthetic chemicals.

13 Although rotation-adapted rootworms arose from the corn/soybean rotation predominant in conventional agriculture, these rootworms may also cause damage in longer rotations, often used in organic and LEI systems, when they lay their eggs in the crop preceding corn.

14 It should be noted, however, that in terms of quantity, field trials for insect resistance and herbicide tolerance still far outnumber those for yield, abiotic stress, and other traits.

15 Bt transgenes produce insect-toxic proteins that are not known to participate in any plant metabolic pathway other than what is needed for their own production, for example, and the CP4-EPSPS gene for glyphosate tolerance substitutes for a similar plant gene in an amino acid synthesis pathway.

16 This number of field trials for ADP-GP is a minimum because the names of most genes used by companies in field trials are not disclosed to the public, having been declared confidential business information (CBI). For example, one of the authors of Giroux et al. (1996) was an employee of Monsanto Co., so the company had some interest in this gene. Thus it is not disclosed in any of Monsanto’s yield field trials, and it is not possible to know whether Monsanto actually used it.

17 Genes discussed by Long et al. (2006) mainly encode enzymes rather than the transcription factors and signal transduction proteins discussed below in the text. But pleiotropic effects (side effects whereby a single gene influences multiple phenotypic traits) are widely observed in genes for other proteins as well (Kuiper et al. 2001). Whether pleiotropic effects occur with these transgenic enzymes, and whether they are harmful, will require careful testing.
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