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Suggested Citation:"Glossary." National Research Council. 1993. Managing Global Genetic Resources: Agricultural Crop Issues and Policies. Washington, DC: The National Academies Press. doi: 10.17226/2116.
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Glossary

A

accession

A distinct, uniquely identified sample of seeds, plants, or other germplasm materials that is maintained as an integral part of a germplasm collection.

active collection

Germplasm accessions that are maintained under conditions of short- and medium-term storage for the purpose of study, distribution, or use.

allele

A contraction of allelomorph; any of a number of alternative forms of a gene. The forms differ in DNA (deoxyribonucleic acid) sequence and affect the functioning of a single gene product(RNA [ribonucleic acid] or protein). New alleles arise from existing ones through mutation. The alleles of a gene occupy the same site or locus on a chromosome.

aneuploid

An unbalanced genome with extra or missing chromosomes, having more or less than an integral multiple of the haploid number of chromosomes.

anther culture

The culturing of the part of the stamen that bears the pollen grains (anther) or of a single pollen grain, as a method of producing haploids, homozygotes, or all-male plants.

apomixis

Asexual reproduction in plants through the formation of seeds without fertilization (agamospermy), or the formation of a new individual from a group of cells without the production of an embryo or seed (vegetable reproduction).

B

base collection

A comprehensive collection of germplasm accessions held for the purpose of long-term conservation; stocks from the

Suggested Citation:"Glossary." National Research Council. 1993. Managing Global Genetic Resources: Agricultural Crop Issues and Policies. Washington, DC: The National Academies Press. doi: 10.17226/2116.
×

base collection replenish exhausted or expired stocks in the active collection.

biological diversity

The variety and variability among living organisms and the ecological complexes in which they occur.

bisexual

Having both sexes.

breeding line

A genetic group that has been selected and bred for their special combinations of traits.

C

characterization

Assessment of the presence, absence, or degree of specific traits that are largely morphological and little influenced in their expression by varying environmental conditions.

chromosome

The structure in the cell nucleus on which genes are located.

clonal propagation

The reproduction of plants through asexual means, such as cuttings, grafts, or tissue culture.

clone

A group of genetically identical individuals that result from asexual, vegetative multiplication; any plant that is propagated vegetatively and that is therefore a genetic duplicate of its parent.

collection

A sample (for example, variety, strain, population) maintained at a genetic resources center for the purposes of conservation or use (an accession); a group of collected samples.

cultivar

A contraction of cultivated variety. See also variety.

cytogenetics

The combined study of cells and genes at the chromosome or cytoplasmic level.

cytoplasmic (mitochondrial) gene

The mitochondrial DNA that is found outside of the nucleus in small, oblate bodies called mitochondria.

D

deoxyribonucleic acid (DNA)

The basis of heredity; the substance of the genetic code.

distribution

To supply adequate samples of genetic resource stocks to breeders and other users.

E

effective population size

The equivalent number of parents if all contributed the same number of progeny to the next generation.

enhancement

The process of improving a germplasm accession by breeding while retaining the important genetic contributions of the accession. This process may entail simple selection.

epistasis

The interaction of genes at different loci. The situation in which one gene affects the expression of another.

evaluation

The assessment of plants in germplasm collection for potentially useful genetic traits, many of which may be environmentally

Suggested Citation:"Glossary." National Research Council. 1993. Managing Global Genetic Resources: Agricultural Crop Issues and Policies. Washington, DC: The National Academies Press. doi: 10.17226/2116.
×

variable (for example, pest or disease resistance, fruit quality, flavor, yield).

exploration

The search for materials in the field.

ex situ conservation

Maintenance or management of an organism away from its native environment. For crop germplasm, this term typically refers to maintenance in seed banks or repositories.

F

folk variety

Local varieties of cultivated plants developed by indigenous farmers in traditional agricultural systems. By modern standards, such varieties are often highly variable genetically.

G

gene

The basic functional unit of inheritance.

gene pool

All the genes within a population.

genetic diversity

In a group such as a population or species, the possession of a variety of genetic traits and alleles that frequently result in differing expressions in different individuals.

genetic drift

The random fluctuations of gene frequencies due to sampling effects or unintended selection; although genetic drift occurs in all populations, its effects are most evident in small populations.

genetic resources

In the context of this report, the term is synonymous with germplasm. See germplasm.

genetic stocks

Accessions that typically possess one or more special genetic traits that make them of interest for research.

genetic vulnerability

The condition that results when a crop or a plant species is genetically and uniformly susceptible to a pest, pathogen, or environmental hazard.

genome

The complete set of chromosomes found in each cell nucleus of an individual. The haploid nucleus of gametes (sperm or egg) contains one genome. The diploid cells that make up the bulk of the living tissue of the plant body contain two sets.

genotype

In the context of this report, plants with a specific complement of genes.

germplasm

Seeds, plants, or plant parts that are useful in crop breeding, research, or conservation because of their genetic attributes. Plants, seed, or cultures that are maintained for the purposes of studying, managing, or using the genetic information they possess.

green revolution

Increased production from the introduction of high-yielding varieties of major grain crops that were also aided by the more intensive use of fertilizers and irrigation.

H

haploid

A cell or organism with a single genome.

heterozygous

Having different alleles at a locus.

Suggested Citation:"Glossary." National Research Council. 1993. Managing Global Genetic Resources: Agricultural Crop Issues and Policies. Washington, DC: The National Academies Press. doi: 10.17226/2116.
×

hybrid

The progeny of a cross between two different species, races, cultivars, or breeding lines.

hybridization

The process of crossing individuals that possess different genetic makeups.

I

inbreeding

The breeding of individuals that are related.

in situ conservation

Maintenance or management of an organism within its native environment. For landraces, this term includes maintenance in traditional agricultural systems.

isoallele

An allele whose effect can only be distinguished from that of the normal allele by special tests.

isoenzyme (isozyme)

Different chemical forms of the same enzyme that can generally be distinguished from one another by electrophoresis.

isogenic

Genetically identical individuals or lines except for one or a few genes.

L

landrace

A population of plants, typically genetically heterogeneous, commonly developed in traditional agriculture from many years of farmer-directed selection, and which is specifically adapted to local conditions.

legume

Any member of the pea or bean family (Leguminosae or alternately, Fabaceae), for example, beans, peanuts, and alfalfa.

M

multiallelic genetic stock

For cultivated plants, includes multiple gene marker stocks that are useful for linkage studies; also stocks with special combinations of loci necessary for the expression of a single trait.

N

neutral allele

Those alleles whose differential contributions to fitness are so small that their frequencies change more owing to drift than to natural selection.

nominal population size

Number of individuals per generation.

null hypothesis

The standard hypothesis used in testing the statistical significance of the difference between the means of samples drawn from two populations. It states there is no difference between the populations from which the samples are drawn. If the probability is 0.05 or less, the null hypothesis is rejected and the difference is said to be significant.

O

obsolete variety

Plant varieties that are no longer grown commercially; such varieties may be maintained in collections for use in breeding programs.

Suggested Citation:"Glossary." National Research Council. 1993. Managing Global Genetic Resources: Agricultural Crop Issues and Policies. Washington, DC: The National Academies Press. doi: 10.17226/2116.
×

outbreeding

The crossing of genetically unrelated plants or animals; crossbreeding.

P

passport data

Information about a sample or specimen and the collection site, recorded at the time of collection. This information should include time of collection, exact location, identifying characteristics, ecological condition of location, names and numbers assigned to the accession by the collector, and any other relevant observations.

perennial crops

Crop plants for which individuals are productive over several years. They include herbaceous perennials that die back annually, such as asparagus, and woody perennials with stems that may live for many years, such as apples, citrus crops, or mangos.

phenotype

The combined expression of the environmental and genetic (hereditary) influences on an organism; the visible characteristics of an organism.

plant breeders' lines

Unreleased lines or parents of hybrids maintained by breeders as part of their working stocks. Breeders usually develop and carry many lines of which only a small number are ever released into commercial production.

pleiotropy

The phenomenon of a single gene being responsible for more than one phenotypic effect.

polymorphic

In the context of this report, plants with several to many variable phenotypic or genetic forms.

population

A group of individuals of the same species that occupy a particular geographic area or region. In general, individuals within a population potentially interbreed with one another.

preservation

Storage of materials in collections under conditions that promote long-term survival and the use of propagation methods that protect genetic integrity during regeneration.

primary gene pool

For plants, a cultivated species and its wild relatives that are readily intercrossed so that gene transfer is relatively simple.

primitive variety

See folk variety.

pyramiding

A strategy for developing long-lasting genetic resistance in a cultivar by combining two or more different genes that confer similar resistance into the same breeding line.

Q

quarantine

Measures that isolate introduced stocks to ensure that they do not carry diseases or pests injurious to the stocks in the importing country.

R

rare

Small populations that are not currently endangered, but that are at some risk of loss.

Suggested Citation:"Glossary." National Research Council. 1993. Managing Global Genetic Resources: Agricultural Crop Issues and Policies. Washington, DC: The National Academies Press. doi: 10.17226/2116.
×

regeneration

Grow-out of a seed accession for the purpose of obtaining a fresh sample with high viability and adequate numbers of seeds.

restriction fragment length polymorphisms (RFLP)

Variation that occurs in the length of DNA fragments resulting from digestion of the extracted DNA with one of several restriction enzymes that cleave DNA at specific recognition sites. Changes in the genetic composition result in fragments of altered length.

S

secondary gene pool

For plants, all the biological species that can be crossed with a cultivated species, but where hybrids are usually sterile. Gene transfer is difficult but not impossible.

seed viability

The ability of a seed to germinate under appropriate conditions.

single-gene or single-trait variants

Lines that carry variants for qualitative characters. Examples include differences in morphological and physiological characters, electrophoretic variation in proteins, and fragment length variation in DNA generated by restriction enzymes.

species

A taxonomic subdivision; a group of morphologically similar organisms that actually or potentially interbreed and are reproductively isolated from other such groups.

T

tertiary gene pool

For plants, those species that can be crossed with a cultivated species only with difficulty and where gene transfer is usually only possible with radical techniques. Biotechnology has, at least in theory, greatly enlarged this pool because transformation (a radical technique) makes possible the introduction of DNA from any species.

tissue culture

A technique for cultivating cells, tissues, or organs of plants in a sterile, synthetic medium; includes the tissues excised from a plant and the culture of pollen or seeds.

tuber

A thickened, compressed, fleshly, usually underground stem that may function as a storage organ for food (starch) or water, or for propagation.

V

variety

A plant type within a cultivated species that is distinguishable by one or more characters. When reproduced from seeds or by asexual means (for example, cuttings) its distinguishing characters are retained. The term is generally considered to be synonymous with cultivar.

W

weed

A plant growing where it is not wanted by humans.

wild and weedy relatives

For plants, those species that share a common ancestry and ecogeographic area with a crop species but that have

Suggested Citation:"Glossary." National Research Council. 1993. Managing Global Genetic Resources: Agricultural Crop Issues and Policies. Washington, DC: The National Academies Press. doi: 10.17226/2116.
×

not been domesticated. Most crops have wild or weedy relatives that differ in their degree of relationship to the crop. The ease with which genes can be transferred from them to the crop varies.

wild species

Species that have not been subject to breeding to alter them from their (wild) state.

Suggested Citation:"Glossary." National Research Council. 1993. Managing Global Genetic Resources: Agricultural Crop Issues and Policies. Washington, DC: The National Academies Press. doi: 10.17226/2116.
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Suggested Citation:"Glossary." National Research Council. 1993. Managing Global Genetic Resources: Agricultural Crop Issues and Policies. Washington, DC: The National Academies Press. doi: 10.17226/2116.
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Suggested Citation:"Glossary." National Research Council. 1993. Managing Global Genetic Resources: Agricultural Crop Issues and Policies. Washington, DC: The National Academies Press. doi: 10.17226/2116.
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Suggested Citation:"Glossary." National Research Council. 1993. Managing Global Genetic Resources: Agricultural Crop Issues and Policies. Washington, DC: The National Academies Press. doi: 10.17226/2116.
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Suggested Citation:"Glossary." National Research Council. 1993. Managing Global Genetic Resources: Agricultural Crop Issues and Policies. Washington, DC: The National Academies Press. doi: 10.17226/2116.
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This anchor volume to the series Managing Global Genetic Resources examines the structure that underlies efforts to preserve genetic material, including the worldwide network of genetic collections; the role of biotechnology; and a host of issues that surround management and use.

Among the topics explored are in situ versus ex situ conservation, management of very large collections of genetic material, problems of quarantine, the controversy over ownership or copyright of genetic material, and more.

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