Glossary

accession

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

active collection

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

allele

One of two or more alternative forms of a gene, differing in DNA (deoxyribonucleic acid) nucleotide sequence and affecting the functioning of a single gene product (RNA [ribonucleic acid] or protein). All alleles of a series occupy the same site or locus on each of a pair of homologous chromosomes.

annual crop

A crop that is grown from seed to harvest within 1 year.

base collection

A comprehensive collection of accessions that are held for the purpose of long-term conservation.

biological diversity

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

breeding line

A group of plants with similar traits that have been selected for their special combinations of traits from hybrid or other populations. It may be released as a variety or used for further breeding.

bulking

The practice of combining several accessions in a collection and managing them as a single accession.

characterization

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



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MANAGING GLOBAL GENETIC RESOURCES: The U.S. National Plant Germplasm System Glossary accession A distinct, uniquely identified sample of seeds or plants, that is maintained as part of a germplasm collection. active collection Comprised of accessions that are maintained under conditions of short-or medium-term storage for the purpose of study, distribution, or use. allele One of two or more alternative forms of a gene, differing in DNA (deoxyribonucleic acid) nucleotide sequence and affecting the functioning of a single gene product (RNA [ribonucleic acid] or protein). All alleles of a series occupy the same site or locus on each of a pair of homologous chromosomes. annual crop A crop that is grown from seed to harvest within 1 year. base collection A comprehensive collection of accessions that are held for the purpose of long-term conservation. biological diversity The variety and variability among living organisms and the ecological complexes in which they occur. breeding line A group of plants with similar traits that have been selected for their special combinations of traits from hybrid or other populations. It may be released as a variety or used for further breeding. bulking The practice of combining several accessions in a collection and managing them as a single accession. characterization Assessment of the presence, absence, or degree of specific traits that are little influenced in their expression by varying environmental conditions.

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MANAGING GLOBAL GENETIC RESOURCES: The U.S. National Plant Germplasm System chemotherapy Treatment with chemicals to eliminate pests or pathogens from a plant or seed sample. 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 (e.g., variety, strain, population) maintained at a genetic resources center for the purposes of conservation or use. community A group of ecologically related populations of various species that occur in a particular geographic area at a particular time. cryobiology Study of the effects of extremely low temperatures on biological systems. cryopreservation Maintaining tissues or seeds for the purpose of longterm storage at ultralow temperatures, typically between −150°C and −196°C; produced by storage above or in liquid nitrogen. cultivar A contraction of cultivated variety. See also variety. cytogenetics The combined study of cells and genes at the chromosome level. electrophoresis The differential movement of charged molecules in solution through a porous medium in an electric field. The porous medium can be filter paper, cellulose, or, more frequently, a starch or polyacrylamide gel. enhancement The process of improving a germplasm accession by breeding in desirable genes from more agriculturally acceptable cultivars, breeding lines, or other accessions, while retaining the important genetic contributions of the accession. For accessions, such as many of horticultural value, this may entail simple selection following one or more crosses. enzyme A protein produced by living cells that acts as a catalyst in essential chemical reactions in living tissues. evaluation The assessment of plants in a germplasm collection for potentially useful genetic traits, many of which may be environmentally variable (e.g., pest or disease resistance, fruit quality, flavor). 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. extinct In the context of this report, the term refers to taxa (e.g., populations, subspecies, species) not found after repeated searches of known and likely areas.

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MANAGING GLOBAL GENETIC RESOURCES: The U.S. National Plant Germplasm System forage Herbaceous plants used as feed for livestock. gene The basic functional unit of inheritance responsible for the heritability of particular traits. 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 resources In the context of this report, the term is synonymous with germplasm. See germplasm. genetic stocks Accessions in a collection that typically possess one or more genetic anomalies or aberrations (e.g., multiple or missing chromosomes, unique genetic markers or mutants) that make them of interest for research. genome A single complete set of the genes or chromosomes of an individual. Typically, gametes such as egg cells contain a single set and are termed haploid, while the somatic cells that comprise the bulk of the living tissue of the plant body contain two sets and are diploid. 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. Plants, seed, or cultures that are maintained for the purposes of studying, managing, or using the genetic information they possess. grow-out The process of growing a plant for the purpose of producing fresh viable seed or for evaluation or characterization. heterozygous Having one or more unlike alleles at corresponding loci of homologous chromosomes. hybrid A cross between two different species, races, cultivars, or breeding lines. hybridization The process of crossing individuals that possess different genetic makeups. in situ conservation Maintenance or management of an organism within its native environment. For landraces this term includes maintenance in traditional agricultural systems. in vitro Maintenance or culture of cells, tissues, or plant parts on a sterile, nutrient medium. land-grant college The Morrill Land-Grant College Act of 1882 provided a trust of public lands, a land grant, to each state to endow a college

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MANAGING GLOBAL GENETIC RESOURCES: The U.S. National Plant Germplasm System where practical education in agriculture and engineering could be emphasized. State land-grant colleges and universities were established from this endowment. landrace A population of plants, typically genetically heterogeneous, commonly developed in traditional agriculture from many years— even centuries —of farmer-directed selection, and which is specifically adapted to local conditions. legume Any member of the pea family (Leguminosae or alternately, Fabaceae), for example, beans, peanuts, and alfalfa. perennial crops Crop plants that are managed to be 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. plant genetic resources Plants from which the genes needed by breeders and other scientists can be derived. Frequently synonymous with germplasm. polymorphic In the context of this report, plants with several to many variable forms. population A group of organisms of the same species that occupy a particular geographic area or region. In general, individuals within a population potentially interbreed with one another. quarantine For plants, regulatory measures that protect plant species against pests and disease that may be borne on or introduced by imported plants. rare In the context of this report, the term refers to taxa with small populations that are not currently endangered, but that are at risk of loss. 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 Variation that occurs within a species in the length of DNA fragments resulting from digestion of the extracted DNA with one of several enzymes that cleave DNA at specific recognition sites. Changes in the genetic composition result in fragments of altered length. seed viability The ability of a seed to germinate under appropriate conditions.

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MANAGING GLOBAL GENETIC RESOURCES: The U.S. National Plant Germplasm System species A taxonomic subdivision; a group of organisms that actually or potentially interbreed and are reproductively isolated from other such groups. state agricultural experiment station Experiment stations were established under the Hatch Act of 1887 that provided annual funding to states to establish agricultural experiment stations under the direction of land-grant colleges. thermotherapy Treatment of plant materials with heat to eliminate or kill pathogens (e.g., viruses) or pests. 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, fleshy, usually underground stem that may function as a storage organ for food (starch) or water, or for propagation. variety A plant type within a cultivated species that is distinguishable by one or more characters. When reproduced from seeds or by asexual means (e.g., cuttings) its distinguishing characters are retained. The term is generally considered to be synonymous with cultivar. voucher A specimen preserved for future reference. wild species Organisms in or out of captivity that have not been subject to breeding to alter them from their native (wild) state.