Glossary
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.