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The definitions below are from the following publication:
Aubry, C., R. Shoal and V. Erickson. 2005. Grass cultivars: their origins,     development, and use on national forests and grasslands in the Pacific Northwest. USDA Forest Service. 44 pages, plus appendices.
It is available here.

A collection of plant material from a particular location. An accession is assigned an identification number, which usually is preceded by the abbreviation PI (plant identification).

In the evolutionary sense, some heritable feature of an individual's phenotype that improves its chances of survival and reproduction in the existing environment.

Area of adaptation
The geographic range in which a given population will thrive, generally described in terms of elevation, temperature range, annual precipitation, and other environmental parameters, as well as in geographic terms.

Breeder seed
The stock seed produced by the breeder or institution that developed and maintains the cultivar. Used to produce foundation seed. Not normally found in commercial channels; the originator or owner of the variety determines the procedure for producing breeder seed and controls breeder seed distribution.

Process intended to maintain the genetic and mechanical purity and identity of commercially produced seed through all steps of production, harvesting, storage, and conditioning. The certification system involves a limited generation or pedigree system comprising four classes of seed: breeder, foundation, registered, and certified. Each class, except for breeder seed, must meet minimum established standards.

Certified seed
The progeny of foundation or registered seed, thus two or three generations removed from breeder seed. Certified seed can be used to produce only common or uncertified seed; it cannot be used to produce any other class of certified seed.

A gradual morphological or physiological change in a group of related organisms across their range, usually associated with environmental or geographic transition.

The process of locating, identifying, and harvesting generally small quantities of plant material.

Common garden study
A scientific study in which many families of a given plant species sampled from an identified geographic area are grown in a common environment. Common garden studies generally include replications in two or more growing environments. Environmentally induced phenotypic differences between the plants are minimized, allowing observation and comparison of genetically adapted traits. Common garden studies are used to determine seed transfer zones.

Common (uncertified) seed
Commercially produced seed that is fourth generation or further removed from cultivar breeder seed. This seed may be given a variety name even though it has not been certified.

A distinct, often intentionally bred subset of a species that will behave uniformly and predictably when grown in an environment to which it is adapted. Also known as variety or release.

A subset of a species that has adapted to a specific geographic environment and as a result has evolved to be genetically distinct from other members of the same species found in different environments.

The relative ability of an individual to survive and produce offspring.

Foundation seed
The earliest (or highest) certified generation of seed available to producers for cultivar seed production. Breeder seed is planted to produce foundation seed, making foundation seed the first-generation progeny.

The term coined by Bateson (1907) for the science of heredity and variation. The study of the patterns of inheritance of specific traits.

Genetic swamping
The homogenization or replacement of local genotypes as a result of either a numerical and/or fitness advantage of introduced plant propagules.

The sum total of the genetic information contained in an organism.

The genetic material that forms the physical basis of heredity and is transmitted from one generation to the next by means of the germ cells. Often synonymous with genetic material. When applied to plants it is the name given to seed or other material from which plants are propagated.

Mating between close relatives.

The sowing and growing out of seed from a given source for the purpose of creating a larger volume of seed.

Refers to a species brought into a geographical area where it does not naturally occur. In terms of cultivars, refers to releases that were originally collected outside the USA or that were collected within the USA from plant materials purposefully introduced and maintained as an introduced population.

Spread of genes from one population or species into another as a result of hybridization.

Local native
Refers to plants that originate in a particular locale and are adapted to specific local conditions.

A plant that occurs naturally in a particular region, state, ecosystem, or habitat without direct or indirect human activity. For cultivars, native refers to releases that were collected from within the USA and that occur naturally in the USA. The definition of native can vary.

A plant or species known to have originated from outside a particular region, state, ecosystem, or habitat but that currently exists in the wild in that area as a self-perpetuating population because of direct or indirect human action. For cultivars, naturalized refers to releases that were present in the U.S. prior to European arrival.

Non-local native
Plant material of a native species that does not originate from genetically local sources.

Used to describe species that do not occur naturally in a given geographic area. The term is similar in meaning to introduced.

Mating between unrelated individuals.

Outbreeding depression
Reduction in vigor or fertility (fitness) resulting from hybridization between genetically distinct individuals or populations of the same species. Often not detected until the 2nd or subsequent generation after hybridization.

Plant materials
Any part of a plant collected and used to propagate the plant. Examples of plant materials include seeds, seedlings, rootstock, branches, and bulbs.

The observable characteristics of an individual, resulting from the interaction between the genotype and the environment in which development occurs.

The number of complete chromosome sets in the cell nucleus (such as diploid, tetraploid, etc.).

Population mixtures of outbreeding species.

Pre-varietal releases
Releases that have not gone through the multiple-generation selection and evaluation process associated with cultivar (variety) releases. There has been less genetic manipulation (selection), so released materials more closely match the original source population. Pre-varietal plant materials can be released more quickly, and fewer (if any) generations occur beyond the original collection site. Pre-varietal germplasms are developed by universities, the USDA Agricultural Research Service, and the NRCS Plant Materials Center. Source-identified, selected, and tested releases are pre-varietal releases. The pre-varietal germplasm (PVG) release concept (also called the “alternative release system”) was developed recently by the NRCS Plant Materials Program to address the growing demand for native plant materials and the need to introduce new plant materials more quickly to the commercial market.

A group of organisms of the same species relatively isolated from other groups of the same species. A locally interbreeding population.

Registered seed
The progeny of foundation seed that is so handled as to maintain satisfactory genetic identity and purity and that has been approved and certified by the certifying agency. This class of seed should be of a quality suitable for production of certified seed.

Released Variety or “Release”
A new variety of proven value that is made available to the public, according to Experiment Station Committee on Organization and Policy (ESCOP) standards, for a conservation purpose. A term used to refer to named plant material that has been intentionally developed for commercial distribution and has gone through some level of testing. A grass cultivar is an example of a release. Although a release is not necessarily a cultivar or a variety, the terms often are used synonymously.

Seed Increase
The sowing and growing out of seed from a given source for the purpose of creating a larger volume of seed.

Seed movement guidelines
Protect the integrity of the natural pattern of adaptive variation of wild populations by restricting seed transfer to areas within which seed can be moved about freely with the expectation that they will grow and reproduce successfully and will produce no adverse genecological effects.

Seed transfer zone
The geographic region within which plant material can be moved without jeopardizing the plant’s ability to thrive. The area within which a plant is evolutionarily adapted. Also the area within which transfer of material of a given species will not jeopardize the genetic integrity of other local populations of the same species. Seed transfer zones are likely to be different for species and for populations within species. Common garden studies are one method to determine appropriate seed transfer zones.

Selected release
Material from plants that have been through some testing and selection and that show desirable superior traits or show promise of performance when compared to other accessions from a common site. Performance of this material has not yet been proven because it has not yet been tested at multiple sites or for more that one generation. Plants may not breed true, and desirable characteristics may not show up in all offspring.

Natural or artificial process that results or tends to result in the survival and propagation of some individuals or organisms but not of others, with the result that the inherited traits of the survivors are perpetuated. In breeding, the directed procedure of picking certain seeds or animals for reproduction in order to influence the traits inherited by the next generation.

Self-fertilization of an organism. In plants, selfing refers to the transfer of pollen from the anther of a flower to the stigma of the same flower or different flowers on the same plant.

Source-identified release
Plant material from a naturally growing population occupying a known or defined geographic area. Material sold commercially may be collected directly from the site or grown under cultivated conditions. No selection or testing has been conducted and seed grown under cultivation should be representative of the entire population.

A group of organisms that is capable of interbreeding to produce fertile offspring. However, this biological test of a species is not always available, so there is also a morphological species concept based on anatomical similarities.

Tested release
Material from plants that have been through testing for more than one generation, including testing on multiple sites with replicated plots to verify performance and heritability of desirable traits. There has been some selection, and the material has proven genetic superiority or possesses distinctive traits for which heritability is stable. Complete area of adaptation may not be known.

An attribute or character of an individual within a species for which heritable differences can be defined.

Differences in the frequency of genes and traits among individual organisms within a population.


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