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... more 10.000 glossed keywords and links to more than 100 figures and schemes, about 100 tables etc. can be obtained in addition to this limited INTERNET version either on CD-ROM or in modified design as book by CRC Press, Taylor & Francis Group, Boca Raton, USA

M1, M2, M3, etc.: symbols used to designate first, second, third, etc. generations after treatment with mutagenic agents meth >>> Figure 1

M2 population: the progeny derived from selfing M1 plants, which themselves are progeny that arise by selfing plants grown from mutagenized seed; recessive mutations, resulting from the seed mutagenesis, are detected in M2 plants, which are homozygous for the mutation gene >>> Figure 1

macerate >>> maceration

maceration: softening of plant tissue by using of enzymes, hydrolic acid, or other means; usually, the middle lamella of the cell walls is degraded without modification of the cell content meth cyto

macerozyme: an enzyme or a mixture of enzymes able to soften plant tissue phys >>> maceration

machinability: in quality testing of cereal flour, a test that measures the stickiness of the dough meth

http://www.wsu.edu/~wwql/php/wheat.php

macrocarpous: carrying or forming big fruits bot

macroclimate: the general climate of a large area, as that of a continent or country, as opposed to microclimate env eco

macroelement: chemical elements, such as nitrogen or phosphorus, that are needed in large amounts as nutrients for plant growth phys agr

macroevolution: evolution above the species level (i.e., the development of new species, genera, families, orders, etc.) evol

macromolecule: a molecule that has a high molecular weight, often a polymer chem

macromutant >>> macromutation

macromutation: a mutation that results in a profound change in an organism, as a change in a regulatory gene that controls the expression of many structural genes, as opposed to micromutation gene

macronutrient: an inorganic element or compound that is needed in relatively large amounts by plants phys

macroscopic: visible to the naked eye micr

macrospore >>> megaspore

macrostylous: showing long stamen bot

maculate: spotted or blotched bot

magnesium (Mg): an element that is found in high concentrations in plants; it plays an important role in the chemical structure of chlorophyll and of membranes and is involved in many enzyme reactions, especially those catalyzing the transfer of phosphate compounds; deficiency can produce various symptoms, including chlorosis and the development of other pigments in leaves chem phys

magnesium chlorate >>> chemical desiccation

magnification: the ratio of the distance between two points in the image to the distance between the two corresponding points in the specimen; the apparent size of the specimen at 25 cm from the eye is considered to be at 1 × micr

maintainer: it is used for maintaining and multiplication of a cytoplasmic male sterile line; usually genotypes containing the normal cytoplasm and recessive at the restorer locus seed >>> Figure 23 >>> hybrid breeding >>> heterosis >>> cytoplasmic male sterility (CMS)

maize gluten: a byproduct of wet milling; it is used as a medium-protein (20-24 %) and medium-fiber (10 %) foodstuff agr >>> Table 15

maize picker: a device to harvest maize agr

major gene: a gene with pronounced phenotypic effects, in contrast to modifier gene, which modifies the phenotypic expression of another gene gene >>> oligogene

major staple: a crop that has a high yield per person-hour, and per unit area; that is reliable from season to season; that produces a food that can be stored; and a food that is easily cooked; there are only three major staples in the world, such as >>> wheat, >>> rice, and >>> maize; every ancient and modern civilisation was based on one of those crops agr

male gametocide: any substance that kills the male reproductive cells of a plant (pollen or pollen mother cells), rendering it male-sterile; male >>> gametocides can be used to convert an inbreeder (e.g. barley) into an outbreeder, for purposes of >>> recurrent mass selection;  treated plants become the female parent, and untreated plants become the male parents; male gametocides can be used for the commercial production of >>> hybrid seed meth

male parent >>> father plant

male sterility: producing no functional pollen bot >>> Figure 23

malformation: faulty or anomalous formation or structure bot gene

Malpighian layer: a protective layer or layers of cells present in the coats of many seeds; it is characteristically made up close-packed, radially placed, heavy-walled in columnar cells without intercellular spaces; the cells often are heavily cutinized or lignified and are relatively impervious to moisture and gases bot

malt: germinated grain used in brewing and distilling meth

maltose: a disaccharide that consists of two alpha-glucose units linked by an alpha-1,4-glycosidic bond chem phys

manganese (Mn): an element that is required in small amounts by plants; it is involved in the light reaction of photosynthesis and also binds proteins; deficiency causes interveinal chlorosis and malformation chem phys

mannitol: a polyhydroxy alcohol that can be synthesized chemically by the reduction of mannose and is present in many plants chem phys

mannose: a hexose, C6H12O6, obtained from the hydrolysis of the ivory nut and yielding mannitol upon reduction chem phys

MANN-WHITNEY test: a statistical test of differences in location for an experimental design involving two samples with data measured on an ordinal scale or better stat

manure: animal excreta with or without a mixture of bedding or litter agr

map (chromosomes, genes): as a verb, to determine the relative or physical position of a gene, DNA molecule, or chromosome segment gene

http://hordeum.oscs.montana.edu/class/cytogenmaprev.pdf

map-based cloning: the isolation of important genes by cloning the gene in question on the basis of molecular maps, where the biochemical function is unknown biot gene

map distance: the distance between any two markers on a genetic map, based on the percentage of crossing-over; the minimum distance between linked genes is 1 % and maximum 50 % gene

http://hordeum.oscs.montana.edu/class/cytogenmaprev.pdf

map length >>> map distance >>> MORGAN unit

mapmaker: an idiomatic description of computer software developed for detection and estimation of linkages; this calculation is based on the maximum likelihood method and often applied for construction of molecular marker maps meth stat biot >>> KOSAMBI formula

mapping: the process and the result of determination of map distances within or between linkage groups; sometimes it refers to the localization of genes or chromosome segments gene >>> physical map

http://hordeum.oscs.montana.edu/class/cytogenmaprev.pdf

marginal farmland: land repeatedly farmed without benefit of humus or chemical replacements agr

marker: a gene of known function and location, or a mutation within a gene that allows studying the inheritance of that gene; phenotype-based, metabolic-based (polyphenol profils, flavonoids, carbohydrates, oils, secondary products), protein-based (isozymes, seed storage proteins, total soluble proteins), and DNA-based (RFLP, by hybridization, and RAPD, SSR, STR, STMS, AFLP, CAPS, EST, Inter-SSR, SNPs, SCAR, PCR-sequencing, by PCR) marker can be distinguished gene meth   >>> negative marker >>> Figure 96 >>> Table 29

marker gene >>> marker

marker-aided selection, marker-assisted selection (MAS): indirect selection exploiting the association between the qualitative variation in a trait (isoenzymes, DNA marker) and the quantitative variation in another trait; it is a strategy permitting plant selection at the juvenile stage from early generations; the essential requirements for MAS in plant breeding are: (1) marker(s) should cosegregate or be closely linked (1 cM or less) with the desired trait, (2) an efficient means of screening large populations for molecular markers should be available, (3) the screening technique should have high reproducibility across laboratories, be economical to use, and should be user friendly meth >>> negative marker >>> Table 29

marsh >>> fen

MAS >>> marker-aided selection

masked symptoms: plant symptoms (e.g., caused by a virus) that are absent under some environmental conditions but appear when the host is exposed to certain conditions of light and temperature phyt

mass emasculation: in hybrid breeding (e.g., in maize), the emasculation of the male flowers by mechanical means meth >>> emasculate >>> detasseling >>> Table 35 >>> Picture 10

mass pedigree (method) selection: a system of breeding in which a population is propagated in bulk until conditions favorable for selection occur; usually, after mass pedigree selection pedigree selection is followed meth >>> Tables 5, 35

http:// www.geneflowinc.com

mass selection (positive or negative): a form of breeding in which individual plants are selected on their individual advantages and the next generation propagated from the aggregate of their seeds; the easiest method is to select and multiply together those individuals from a mixture of phenotypes, which correspond to the breeding aim (positive mass selection), it is still applied in cross-pollinating of vegetable species, such as carrots, radishes, or beetroots, in order to improve the uniformity; when all undesired off-types are rouged in grown crop population and the remaining individuals are propagated further, the method is termed negative mass selection; negative mass selection is no longer an adequate breeding method for highly advanced varieties; it is usually applied in multiplication of established varieties (i.e., for seed production in order to remove diseased plants, casual hybrids, or other defects) meth >>> Figures 39, 40 >>> Tables 5, 35

mass spectrometry: a technique that allows the measurement of atomic and molecular masses; material is vaporized in a vacuum (ionized) and then passed first through a strongly accelerating electric potential, and then through a powerful magnetic field; it serves to separate the ions in order of their charge (i.e., mass ratio); detection is made using an electrometer, which measures the force between charges and hence the electrical potential meth phy >>> gas chromatograph

master nursery >>> cohort >>> check variety

mate: a unisexual individual that is involved in sexual reproduction gene >>> Table 35

maternal effect: any nonlasting environmental effect or influence of the maternal genotype or phenotype on the immediate offspring gene

maternal inheritance: phenotypic differences found between individuals of identical genotype due to an effect of maternal inheritance gene

mating: the combination of unisexual individuals with the aim of sexual reproduction gene >>> Table 35

mating design: the pattern of pollination set up between individuals for an artificial crossing program, e.g., single pair mating, double pair mating there each parent participates in one or two crosses meth

mating group: a group of individuals that gives the chance for mating among one another on the basis of genetic prerequisites gene

mating system: the pattern of mating in sexually reproducing organisms; two types of mating systems are: (1) random mating and (2) assortative mating (genetic assortative mating, genetic disassortative mating, phenotypic assortative mating, phenotypic disassortative mating) gene >>> Table 35

mating type: the genetic properties of an individual for a particular type of mating gene >>> Table 35

matroclinal: with hereditary characteristics more maternal than paternal (e.g., in certain banana hybrids) bot

matroclinous >>> matroclinal

matromorphy: resembling the female parent in morphology bot

maturation: the completion of development and the process of ripening phys

maturation division >>> meiosis

mature: fully differentiated and functionally competent cells, tissues, or organisms phys

mature resistance >>> adult resistance

maturity >>> mature

maximum likelihood method: a statistic method of linkage estimation depending on maximizing of the log likelihood; the method leads to an efficient and sufficient statistic if one exists stat

maysin: a naturally occurringC-glycosylflavone glycoside present in silks of maize; it confers resistance to corn earworm (Helicoverpa zea); the adoption of high-pressure liquid chromatography procedures allowed the identification of analogues, such as (apimaysin (AP), 3-methoxymaysin (ME), isoorientin and other luteolin derivatives) as well as other compounds, such as chlorogenic acid  (CHA), which demonstrated antibiotic activity to the maize earworm; the generally accepted level of maysin in silks required to reduce maize earworm larval weights by 50 % is approximately 0.2 % of silk fresh weight; recently, two new maize populations were derived for high silk maysin; the two populations were named the exotic populations of maize (EPM) and the southern inbreds of maize (SIM); QTL analysis was employed to determine which loci were responsible for elevated maysin levels in inbred lines derived from the EPM and SIM populations; the candidate genes consistent with QTL position included the p (pericarp color), c2 (colorless2), whp1 (white pollen1), and in1 (intensifier1) loci; the role of these loci in controlling high maysin levels in silks was tested by expression analysis and use of the loci as genetic markers onto the QTL populations; the studies support p, c2 and whp1, but not in1, as loci controlling maysin; the p locus regulates whp1 transcription and that increased maysin in these inbred lines was primarily due to alleles at both structural and regulatory loci promoting increased flux through the flavone pathway by increasing chalcone synthase activityphyt phys

mDNA >>> messenger DNA

ME >>> mega-enviroment

meal: the byproduct of oilseeds; used as a high-protein animal feed agr

mean: the sum of an array of quantities divided by the number of quantities in the group stat

mean square: the square of the mean variation of a set of observations around the sample mean stat >>> variance

measurement error: refers to errors in estimates resulting from incorrect responses gathered during the data collection phase of a survey stat

mechanical inoculation: a method of transmitting the pathogen from plant to plant; for example, sap from diseased plants or a defined inoculum are rubbed on test-plant leaves that usually have been dusted with carborundum or other abrasive materials; it is applied in experimental testing of plant resistance phyt

mechanical purity: refers to the degree of freedom of a seed lot from seeds of other crop kinds, weed seeds and inert matter seed

media composition: different supplements to the nutritive substance provided for the growth of a given plant in the laboratory biot

median centromere: a centromere that is located midway of chromosomes resulting in two equal-long arms cyto

medical plants: plants that are or have been used medicinally (e.g., chamomile) hort >>> chamomile

medium (media pl): any material in or on which cultures are grown prep

medium-term seed storage: with a storage time of about ten years meth >>> long-term storage

megabase cloning: the molecular cloning of very large DNA fragments (>500 bp) meth biot

mega-environment (ME): a broad, not necessarily contiguous area, occurring in more than one country and frequently transcontinental, defined by similar biotic and abiotic stresses, cropping system requirements, consumer preferences, and by a volume of production; the concept was introduced by CIMMYT in 1988 to address the needs of diverse wheat-growing areas of the world eco agr >>> CIMMYT

http://www.plantstress.com

megagametogenesis: the development of the female gametophyte from a functional megaspore bot

megagametophyte >>> embryo sac

megaspore: one of the four cells formed in the ovule of higher plants as a result of meiosis or sexual cell reduction division; one of these later undergoes mitosis to give rise to the female gamete bot

megaspore mother cell: a diploid cell in the ovary that gives rise, through meiosis, to four haploid megaspores bot

megasporocyte >>> embryo sac

megasporogenesis: the development of the megaspore from the archesporial cell bot

mega-yeast artificial chromosomes (mega YAC): a large (>500 bp) piece of DNA that has been cloned inside a living yeast cell; while most bacterial vectors cannot carry DNA inserts that are larger than 50 bp, and standard YACs typically cannot carry DNA pieces that are larger than 500 bp, mega YACs can carry DNA pieces (chromosomes) as large as one million bp biot

meiocyte: the sporocyte giving rise to the embryo sac and to pollen grains bot

meiosis: a type of nuclear division that occurs at some stage in the life cycle of sexually reproducing organisms; by a specific mechanism the number of chromosomes is halved to prevent doubling in each generation; genetic material can be exchanged between homologous chromosomes; there are different stages: leptotene, zygotene, pachytene, diplotene, diakinesis, metaphase I, anaphase I, telophase I, interphase, metaphase II, anaphase II, telophase II, microspore formation bot cyto >>> Figures 15, 28

meiotic crossing-over >>> chiasma

meiotic cycle >>> meiosis

meiotic duration: the time needed for completing the cell cycle from prophase to telophase under certain conditions cyto

meiotic mutation: used to elucidate several areas of genetic research, e.g., it involves gene-centromere mapping by half-tetrad analysis with 4x x 2x crosses (potato), where the 2x parent forms 2n pollen by either first-division restitution (FDR, ps/ps) or second-division restitution (SDR, pc/pc); since two of four strands of a bivalent are recovered together in 4x progeny from crossing a 4x nulliplex (aaaa) with a 2x heterozygous (Aa), the frequency of 4x nulliplex progeny provides an estimate of gene-centromere map distance; through half-tetrad analysis; the second application involves pyramiding of distinct meiotic mutations in the same genetic background, e.g., clones with the doubly homozygous genotype ps/ps, sy-3/sy-3 are able to produce 2n gametes by a mechanism equivalent to FDR without crossover; these gametes transmit the parental genotype virtually intact to their progenies, the FDR non-crossing-over (NCO) 2x clones provide a homogeneous sample of heterozygous gametes for testing the parental value of 4x clones; factorial 4x x 2x crosses using 2x (FDR-NCO) male parents allow  to estimate the relative contribution of the random meiotic products (from the 4x parents) and the "somatic" (non-recombinogenic) male genome to the phenotypic expression of quantitative traits; another application of meiotic mutants has been to permit genetic inference about the chromosomal (physical) location of quantitative trait loci (QTL) controlling important traits (e.g., in potato); a large range of 4x cultivars can be crossed with a collection of full-sib 2x clones able to transmit different fractions of their heterozygosity via 2n gametes; tuber yield of the progenies then can be determined at different environments; one group of progenies is derived from FDR with crossing-over (FDR-CO) clones, where the 2x parent transmits about 80 % of the heterozygosity to the 4x progeny; the other group is derived from FDR-NCO clones in which the 2x parent transmits almost 100 % of its heterozygosity and epistasis to 4x progeny; therefore, one can expect higher yields with 100 % transmission of heterozygosity vs. 80 % heterozygosity; however, no significant difference in total tuber yield between the two groups is found; these results can be interpreted that loci with a major effect on yield are located between centromeres and proximal crossovers, since these regions are in common between the two groups of 2x clones; all the genetic analyses using meiotic mutants thus far are converging to one interesting notion: QTL with a major effect on yield are predominantly located in genomic regions with reduced levels of recombination; in this context, breeding programs should develop strategies to maximize the transfer of heterozygosity to proximal loci, since theoretical models also indicated that deleterious mutations would preferentially accumulate in these regions of the 4x potato chromosomes gene cyto meth

melting temperature (Tm): the temperature at which the two strands of a double-stranded DNA molecule come apart; a short (<18 nucleotides) oligonucleotides Tm value (°C) is estimated by the formula: Tm = (number of A + T) x 2 + (number of G + C) x 4 chem meth

membrane: a sheetlike structure, 7-10 nm wide, that forms the boundary between a cell and its environment and also between various compartments within the cell; it is composed of lipids, proteins, and some carbohydrates; it functions as a selective barrier and also as a structural base for enzymes bot

Mendelian character: a character that follows the laws of inheritance formulated by G. MENDEL gene

Mendelian inheritance >>> MENDEL’s laws of inheritance

Mendelian population: an interbreeding group of organisms that share a common gene pool gene

Mendelian ratio: the segregation rations according to MENDEL’s laws of inheritance gene >>> Figure 6 >>> Table 2

Mendelism >>> MENDEL’s laws of inheritance

mendelize: to segregate according to MENDEL’s laws of inheritance gene

MENDEL’s laws of inheritance, Mendelian laws of inheritance: the inheritance of chromosomal genes on the basis of chromosome theory of heredity; three laws are considered: (1) law of dominance or of uniformity of hybrids (2) law of segregation (3) law of independent assortment gene >>> Figure 6 >>> Table 2

mercaptan >>> thiol

mericlinal: it refers to a chimera in which the inner tissue has a different genetic constitution than the surrounding outer tissue bot >>> chimera >>> Figure 72

meristem: a group of plant cells that is capable of dividing indefinitely and whose main function is the production of new growth; meristematic cells are found at the growing tip of a root or a stem (apical meristem), in cambium (lateral meristem) and also within the stem and leaf sheaths (intercalary meristem of grasses) bot phys

meristematic: pertaining to the meristem bot

meristematic tip: the meristematic dome and one pair of leaf primordia; it is commonly used as explants, particularly to produce virus-free plant material bot hort >>> meristem

meristem (tip) culture: the culture of an explant consisting only of a meristematic part biot

merogony: an individual with the egg cytoplasm from one parent and the egg nucleus from the other parent gene

mesenchyme: an embryonic type of connective tissue bot

mesocarp: middle layer of the fruit wall bot >>> pericarp

mesocotyl: an elongated portion of the seedling axis between the point of attachment of the scutellum and the shoot apex of, for example, a grass seedling; it is recognized as a compound structure that is formed by the growing together of the cotyledon and the hypocotyl bot

mesoderm: the middle layer of embryonic cells between the ectoderm and the endoderm bot

mesophyll: internal parenchyma tissue of a plant leaf that lies between epidermal layers; it functions in photosynthesis and in storage of starch bot

mesophyll explant: an explant prepared from internal parenchyma tissue biot >>> mesophyll

mesophyte: a plant with an intermediate water requirement bot

messenger DNA (mDNA): a single-stranded DNA that acts as a messenger of the protein biosynthesis gene

messenger RNA (mRNA): a single-stranded RNA molecule responsible for the transmission to the ribosomes of the genetic information contained in the nuclear DNA; it is synthesized during transcription and its base sequencing exactly matches that of one of the strands of the double-stranded DNA molecule gene

metabolic pathway: a sequential series of enzymatic reactions involving the synthesis, degradation, or transformation of a metabolite; the pathway can be linear, branched, or cyclic and directly or indirectly reversible gene

http://www.drastic.org.uk/

metabolism: the chemical changes within the living cell; it is sum of all the physical and chemical processes by which the living protoplasm is produced and maintained and by which energy is made available for the use of the organism phys

http://www.drastic.org.uk/

metabolite: a substance taking part in metabolism phys

metacentric: applied to a chromosome that has its centromere in the middle cyto >>> Figure 11

metaphase: a stage of mitosis or meiosis at which the chromosomes move about within the spindle until they eventually arrange themselves in its equatorial region; in metaphase I (MI) of meiosis, the chromosomes of a genome line up within the cell at a position referred to as the equatorial plate; spindle fibers form, which link each chromosome of a homologous pair to a different pole of the cell; the orientation of the chromosomes relative to the two poles seems to be random; the number of different combinations of chromosomes that can occur due to their orientation at MI is defined by the formula 2n–1, where n is the number of chromosomes in the genome; for example, there are two combinations possible with two chromosome pairs, four combinations with three chromosome pairs, and eight combinations with four chromosome pairs cyto >>> Figure 15

metaphase arrest: the stopping of cell division at mitotic or meiotic metaphases, usually by application of specific agents cyto meth

metaphase plate: the grouping of the chromosomes in a plane at the equator of the spindle during the metaphase stage of mitosis and meiosis cyto >>> Figure 15

metapopulation: the some of multiple sublined breeding populations may be referred to as a metapopulation meth

metaxenia: the influence of pollen on maternal tissue of the fruit bot

methionine (M): sulfur containing nonpolar amino acid chem phys

method of overstored seeds: in pedigree breeding of allogamous crop plants (e.g., in rye), an effective method of regulating cross-fertilization; usually, a greater number of individual plants is harvested from a genotypic mixture of a certain population; their progenies are sown as A families in smaller plots while a half of the seed of all elite plants is retained in reserve; those A families meeting all the requirements are not directly multiplied but the remaining seed of the corresponding elite plants is sown in the following year; it enters a so-called A' family trial; in this way the economically valuable traits of the A family can be definitely evaluated after maturity; the best A families determined for further breeding have already been pollinated by a pollen mixture that also contains pollen of less valuable plants meth >>> Figure 4 >>> Table 35

http:// www.geneflowinc.com

methotrexate: a toxic folic acid analogue, C20H22N8O5, that inhibits cellular reproduction chem phys biot

methylation: the introduction of a methyl group into an organic compound; methylation of specific nucleotides within a target site of a restriction enzyme can protect the DNA against attack by that enzyme chem phys

2-methyl-butadiene >>> isoprene

3-methyl-2-cyclohexene-1-one syn methylcyclohexenone (MCH): it is used in forests to protect live trees from spruce beetles and Douglas fir beetles; the volatile, naturally occurring chemical acts as a beetle repellent; when small amounts of MCH are attached to dead trees, beetles are prevented from aggregating on the dead trees and from large scale reproduction fore phyt

1-methylcyclopropene (MCP): it is used for extending the lifetime of cut flowers and potted ornamental plants; it is approved for use only in enclosed spaces such as greenhouses and shipping containers hort meth

methylene blue: a vital staining agent for chromosomes micr

methyl-methanesulfonate: a frequently used, very efficient chemical mutagen; it acts by adding methyl to guanine; thus, it causes base pairing errors as it binds to adenine prep gene

metric character: a trait that varies more or less continuously among individuals, which are therefore placed into classes according to measured values of the trait; it is also called “quantitative character” gene

microarray(s): a tool to examine the expression levels and intertwined interactions among genes and among their products; complementary DNA of interest is affixed to a glass slide in an ordered array; the expression level is determined by the binding to cDNA; a small glass, or filter, square may contain probes for thousands of gene products; in statistics, microarray is a >>> block design with blocks of size 2; the concept arose in DNA testing, where each array is probed with two DNA samplesbiot meth stat

microbe: a microorganism, especially a disease-causing bacterium bot phyt >>> microorganism

microbial >>> microbe

microclimate: the atmospheric characteristics prevailing within a small space eco env >>> macroclimate

microdissection >>> micromanipulation

microelement >>> trace element >>> macroelement >>> micronutrient

microevolution: evolutionary change within species that results from the differential survival of the constituent individuals in response to natural selection; the genetic variability on which the selection operates arises from mutation and sexual recombination in each generation evol

microgametogenesis: the development of the microgametophyte (pollen grain) from a microspore bot

microinjection: injection performed under a microscope using a fine microcapillary pipette (e.g., into a single cell or cell part) biot

micromanipulation: manipulation or surgery done while viewing the object through a microscope and often carried out with the aid of an injection or dissection of substances or particles biot >>> microinjection

micromanipulator: the facility usually attached to a microscope in order to carried out micromanipulation micr >>> micromanipulation

micrometer: a unit of measurement frequently used in microscopy (1 m = 10-6 meter); in older usage also known as micron (1) meth

micromutant >>> macromutant

micron >>> micrometer

micronucleolus: a small nucleolus that may arise by nucleolar budding in the course of nucleolar degeneration cyto

micronucleus: the smaller nucleus as distinguished from the larger nucleus, produced during telophase of mitosis or meiosis by lagging chromosomes or chromosome fragments derived from spontaneous or induced chromosome aberrations cyto

micronutrient: an inorganic element or compound that is needed in relatively small amounts by plants phys >>> microelement >>> trace element

microorganism: literally, a “microscopic organism”; the term is usually taken to include only those organisms studied in microbiology (bacteria, fungi, microscopic algae, protozoa, viruses) bio

microphotography: photography requiring optical enlargement meth micr

microplot: microplots are used to minimize the amount of seed or space required to evaluate a group of individuals; the number of plants in a microplot differs among crops; when short rows are used as microplots, the plant density is comparable to that of larger row plots; in unbordered microplots, the effect of interplot competition has to be considered when determining an appropriate distance among the plots meth

http://www.drastic.org.uk/

microprojectile >>> high-velocity microprojectile transformation

microprojectile bombardment >>> high-velocity microprojectile transformation

micropropagation: vegetative propagation by application of tissue culture; it is usually conducted in growth chambers; several stages are distinguished: stage I - establishment of small fragments of stock plant(s) in tissue culture, stage II - multiplication of >>> propagules; the most common method is through stimulation of branching and subsequent division of shoot clumps on smaller explants, which are then placed on a fresh medium; through repetition of the process, number of initial propagules can increase a million times in one year; stage III - preparation of propagules for transfer to normal growing conditions through rooting or elongation of shoots, stage IV - establishment of stage II or III propagules in normal growing conditions - usually in soil or potting mix in a greenhouse seed biot >>> in vitro propagation

micropylar >>> micropyle

micropyle: a canal in the coverings of the nucellus through which the pollen tube usually passes during fertilization; later, when the seed matures and starts to germinate, the micropyle serves as a minute pore through which water enters bot

micro-RNA (miRNA): a tiny piece of RNA, about 21 to 23 bases in length, that binds to matching pieces of messenger RNA to make it double-stranded and decrease the production of the corresponding protein; micro-RNA's were first discovered in the roundworm C. elegans in the early 1990s and are now known in many species, including plants biot meth

microsatellite DNA: pieces of small DNA sequences that are repeated (appear repeatedly in sequence within the DNA molecule) adjacent to a specific gene within the DNA molecule; thus, microsatellites are linked to that specific gene biot >>> microsatellite marker

http://wheat.pw.usda.gov/ITMI/Repeats/index.shtml

microsatellite marker: microsatellites or simple sequence repeats are a type of molecular markers; microsatellites consist of tandem repeats of 1-6 nucleotide motifs; the repeats usually are in units of ten or more, although repeats as small as six units have been found; the repeats can be (1) perfect tandem repeats, (2) imperfect (interrupted by several non-repeat nucleotides), or (3) compound repeats; they are well-distributed throughout a genome; microsatellites can be amplified by the polymerase chain reaction (PCR) using a pair of primers flanking the repeat sequence; the polymorphism between different individuals is due to the variation in the number of repeat units; each locus can have many alleles; one advantage of microsatellites is that they are mostly codominant, which make them easily transferable between genetic maps of different crosses in the same or closely related species, in contrast with RAPDs, which are dominant and therefore new maps have to be generated for every cross; several microsatellite-primer pairs may be used simultaneously, thus reducing time and costs; the relatively simple interpretation and genetic analysis of single-locus markers make them superior to multi-locus DNA marker types such as RAPDs; microsatellites are also called “simple sequence repeats” (SSRs), “simple tandem repeats” (STRs) or “simple sequences” (SSs) gene >>> Table 29

http://wheat.pw.usda.gov/ITMI/Repeats/index.shtml

microsatellite-primed PCR (MP-PCR): a technique resulting in RAPD-like patterns after agarose gel electrophoresis and ethidium bromide staining; the MP-PCR technique is more reproducible than RAPD analysis because of higher stringency biot >>> random amplified polymorphic (RAPD) technique

microscope: an optical instrument having a magnifying lens or a combination of lenses for inspecting objects too small to be seen distinctly by the unaided eye micr

microscopic slide >>> glass slide

microsome >>> minichromosome

microsporangium: a sporangium (e.g., pollen sac) that produces the microspores (pollen) bot

microspore: the first cell of the male gametophyte generation of Angiospermae and Gymnospermae, later to form the pollen grain bot

microspore culture: it refers to the in vitro culture of pollen grains to obtain haploid callus or haploid plantlets directly from the pollen grains; microspore cultures differ from pollen cultures by the stage of development in gametogenesis biot >>> Figures 17, 26 >>> Table 7

microspore mother cell: one of the many cells in the microsporangium (anther) that undergo microsporogenesis to yield four microspores, as opposed to megaspore mother cell bot

microsporocyte >>> pollen mother cell (PMC)

microsporogenesis: the development of microspores from the microspore mother cell bot >>> meiosis

microstylous: showing a short stamen bot

microsurgery >>> micromanipulation

microsynteny: genomic relationships at gene level >>> synteny

microtome: a machine for cutting thin slices of embedded tissue; these sections may be stained and examined with the light or electron microscope prep

microtubule: a tubular structure, 15-25 nm in diameter, of indefinite length and composed of subunits of the protein tubulin; it occurs in large numbers in all eukaryotic cells, either freely in the cytoplasm or as a structural component of organelles; they form part of the structure of the mitotic spindle, which is responsible for the movement of chromosomes during cell division cyto

micrurgy >>> micromanipulation

mictic >>> amphimictic

micton: it refers to a species of wide distribution, which is the result of hybridization of two or more species; all individuals are cross-fertile and have ancestral genotypes; apomixis is not present gene

mid rip: the central, thick, linear structure that runs along the length of a plant lamina; it occurs in true leaves as a vein running from the leaf base to the apex; it provides support and is a translocative vessel bot

migration: the movement of individuals or their propagules from one area to another eco

milky stage: in cereals, the stage of “milk” ripening of caryopses at which the endosperm shows a milky consistency phys >>> Table 13

milling: the processes in which cereal grains are subjected to grinding followed by sifting, sizing, or other separation techniques, for example, in wheat, the grain is tempered to approximately 15-17 % moisture, which facilitates the separation of the endosperm, the pericarp, and embryo meth agr

Millipore filter: a disc-shaped synthetic filter having holes of specified diameter (0.005-8 µ) through its surface prep

mineralization: the conversion of organic tissue to an inorganic state as a result of decomposition by the organic content agr

mineral soil: a soil containing <20 % organic matter or having a surface organic layer <30 cm thick agr

minichromosome: a very small chromosome, usually as a result of chromosome aberrations cyto

miniprep: an abbreviation for minipreparation; it refers to a small-scale preparation of plasmid or phage DNA commonly used after cloning to analyze the DNA sequence inserted into a cloning vector biot

minisatellite: highly polymorphic DNA markers comprised of a variable number of tandem repeats that tend to cluster near the telomeric ends of chromosomes; the repeats often contain a repeat of 10 nucleotides; they are usful tools for genetic mapping meth biot >>> microsatellite

minor crops: crops that may be high in value but that are not widely grown (e.g., many fruits, vegetables, and trees) agr

minor element >>> trace element

minor gene: a gene that individually exerts a slight effect on the phenotype gene >>> modifying (modifier) gene

minor oilseeds: oilseed crops other than soybeans and peanuts (e.g., in some countries, sunflower seed, canola, rapeseed, safflower, mustard seed, and flax seed) agr

minute fragment (of a chromosome): usually very tiny chromosome segments as a result of chromosome aberrations cyto

miRNA>>> micro-RNA

misdivision: aberrant chromosome division in which no longitudinal but transversal separation of the centromere occurs; the consequence may be telocentric chromosomes cyto >>> Figure 37

mismatch repair: any of the several cellular mechanisms for correction of mispaired nucleotides in double-stranded DNA gene >>> mismatching

mismatching: a region of DNA in a heteroduplex where bases cannot pair gene >>> mismatch repair

mispairing: the presence in one chain of a DNA double helix of a nucleotide that is not complementary to the nucleotide occupying the corresponding position in the other chain gene

missense mutation: a mutant in which a codon has been altered by mutation so that it encodes a different amino acid; the result is almost always the production of an inactive or possibly unstable protein and/or enzyme gene

mitochondrion (mitochondria pl): an oval, round, or thread-shaped organelle, whose length averages 2 µm and that occurs in large numbers in the cytoplasm of eukaryotic cells; it is a double-membrane-bound structure in which the inner membrane is thrown into folds (cristae) that penetrate the inner matrix to varying depths; it is a semi-autonomous organelle containing its own DNA and ribosomes and reproducing by binary fission; it is the major site of ATP production and thus of oxygen consumption in cells bot

mitomycin C: a form of a family of antibiotics produced by Streptomyces caespitosus; it prevents DNA replication by crosslinking the complementary strands of the DNA double helix chem phys

mitosis: the process of nuclear division by which two daughter nuclei are produced, each identical to the parent nucleus; before mitosis begins each chromosome replicates to two sister chromatids; these then separate during mitosis so that one duplicate goes into each daughter nucleus; in contrast to the prophase of meiosis I, the prophase of mitosis does not involve pairing of chromosomes or crossing-over between the homologous chromosomes; during metaphase, the individual chromosomes line up at the equatorial plate of the cell and a spindle fiber develops that links each of their chromatids to one of the two poles in the cell; the chromatids of each chromosome separate and move to opposite poles at anaphase; at telophase, a nuclear membrane develops around the chromosomes to define the nucleus of the cell; a cell wall is formed cyto

mitotic apparatus: an organelle consisting of three components: (1) the asters, which form the centrosome, (2) the gelatinous spindle, and (3) the traction fibers, which connect the centromeres of the various chromosomes to either centrosome bot

mitotic crossing-over >>> somatic crossing-over

mitotic cycle: the sequence of steps by which the genetic material is equally divided before the cell division into two daughter cells happens cyto

mitotic index (MI): the fraction of cells undergoing mitosis in a given sample; usually the fraction of a total of 1,000 cells that are undergoing division at one time cyto meth

mitotic inhibition: induced or spontaneous inhibition of the mitotic division phys cyto

mitotic poison: any substance that hampers the proper mitosis cyto phys

mitotic recombination: the recombination of genetic material during mitosis and the process of asexual reproduction; the mechanism for the production of variation in heterokaryons cyto

mitotic spindle: the spindle-shaped system of microtubules that, during cell division, traverses the nuclear region of eukaryotic cells; the chromosomes become attached to it and it separates them into two sets, each of which can be enclosed in the envelope of a separate daughter nucleus cyto

mixograph:an instrument used to record the mixing behaviour of wheat flour doughs; mixing torque is plotted as a function of time meth

mixoploid: cell populations in which different cells show different chromosome numbers cyto >>> mosaicism

mixture: it consists of seed of more than one kind or variety, each present in excess of at least 5% of the whole seed >>> blend

mobile element >>> transposable element

modal value >>> mode

mode: the value of the variate at which a relative or absolute maximum occurs in the frequency distribution of the variate stat

mode of reproduction: two general modes of reproduction are distinguished: (1) sexual and (2) asexual; sexual reproduction involves the union of male and female gametes derived from the same or different parents; asexual reproduction occurs by multiplication of plant parts or by seed production that does not involve the union of sexual gametes; the breeding procedures are dependent on the mode of reproduction bio gene

modern varieties: varieties developed by breeders in the formal system seed

modificability: the ability of phenotypic variation of a particular genotype in response to varying environmental conditions gene

modification: nonheritable morphological or physiological changes induced by varying abiotic or biotic influences gene; in molecular biology, modification of DNA by DNA methylases occurs after replication; site-specific methylation protects the DNA (e.g., of bacteria), which synthesize restriction endonucleases biot

modifying (modifier) gene: a gene that modifies the phenotypic expression of another gene gene

moisture tension: the force at which water is held by soil: it is expressed as the equivalent of an unit column of water in centimeters agr

moisture meter >>> hygrometer

moisture tension: the force at which water is held by soil: it is expressed as the equivalent of an unit column of water in centimeters agr

mol(e) (Mmol): gram molecular weight chem >>> molecular weight (MW)

molasses: residue of the beet sugar or sugarcane production agr

moldboard: the curved metal plate in a plough that turns over the earth from the furrow agr

moldboard plough: a plough with a point and a heavy curved blade for breaking the soil agr

molecular cloning: DNA segments of different sizes of prokaryotic or eukaryotic origin are identically multiplied as a part of bacterial plasmids or phages: the alien DNA is incorporated into the host DNA ring molecule; by the rapid division of the host cells the alien DNA segments are simultaneously cloned; subsequently, those cloned DNA segments can be excised, separated and purified for further utilization biot

molecular genetics: a branch of genetics that deals with molecular aspects of genetic mechanisms gene

molecular hybridization: the annealing of previously purified and denatured DNA strands by different means gene meth >>> DNA hybridization

molecular marker: particular DNA sequences and/or segments that are closely linked to a gene locus and/or a morphological or other characters of a plant; those segments can be detected and visualized by molecular techniques; roughly, three groups of markers can be classified: (1) hybridization-based DNA markers such as restriction fragment length polymorphisms (RFLPs) and oligonucleotide fingerprinting; (2) PCR-based DNA markers such as random amplified polymorphic DNAs (RAPDs), which can also be converted into sequence characterized amplified regions (SCARs), simple sequence repeats (SSRs) or microsatellites, sequence-tagged sites (STS), amplified fragment length polymorphisms (AFLPs), inter-simple sequence repeat amplification (ISA), cleaved amplified polymorphic sequences (CAPs) and amplicon length polymorphisms (ALPs); (3) DNA chip and sequencing-based DNA markers such as single nucleotide polymorphisms (SNPs) gene biot

http://wheat.pw.usda.gov/ITMI/Repeats/index.shtml

molecular weight (MW): the sum of the atomic weights of all of the atoms in a given molecule chem

molecule: that ultimate unit quantity of a compound that exists by itself and retains all the chemical properties of the compound chem

molybdenum (Mo): an element that is required in small amounts by plants and is found largely in the enzyme nitrate reductase; deficiency leads to interveinal chlorosis chem phys

monad: a meiocyte-derived individual cell instead of a tetrad as a result of meiotic disturbances cyto

monoallelic: applied to a polyploid in which all alleles at a particular locus are the same (in a tetraploid—A1A1A1A1) as opposed to diallelic (in a tetraploid—A1A1A1A2), triallelic (in a tetraploid—A1A1A2A3), tetraallelic (in a tetraploid—A1A2A3A4), etc. gene

monobrachial: a chromosome with a terminal centromere cyto >>> telocentric >>> Figures 11, 37

monocarpic: bearing one fruit bot

monocentric chromosome: a chromosome with only one centromere cyto >>> Figure 11 >>> neocentric >>> polycentric

monocentric crop plant: a crop plant species that has only one center of origin evol >>> center of diversity

monoclonal: describing genetically identical cells produced from one clone gene

monoclonal antibody: an antibody preparation that contains only a single type of antibody molecule; monoclonal antibodies are produced naturally by myeloma cells; a myeloma is a tumor of the immune system; a clone of cells producing any single antibody type may be prepared by fusing normal lymphocyte cells with myeloma cells to produce a hybridoma meth sero

monoclonal blocks: a deployment option for clones or for families in monofamily blocks in which each clone (family) is established in a pure block; diversity may be maintained by a mosaic of blocks of different genetic entries meth

monocot: an abbreviated name for monocotyledon, referring to plants having single-seed leaves; flower parts arranged in threes or multiples thereof, parallel-veined leaves, closed vascular bundles arranged randomly in the stem tissue bot >>> Table 32

monocotyledonous: having one cotyledon bot >>> monocot

monoculm mutant: a mutant form that shows only one culm instead of normally more (e.g., in wheat) gene

monoculture: the growing over a large area of a single crop species or of a single variety of a particular species agr

monoecism: the condition in plants that have male and female flowers separated on the same plant (e.g., in maize or pumpkin) bot >>> Table 18

monogenic: a trait controlled by the alleles of one particular locus, as opposed to digenic, trigenic oligogenic, or polygenic gene >>> Table 33

monogenic resistance: resistance determined by a single gene phyt

monogenomatic >>> monohaploid

monogenotypic >>> clone variety

monogerm(ous): a fruit of, for example, sugarbeet containing only one ovule in contrast to a multigerm fruit, which represents an aggregate fruit containing several ovule units bot seed >>> Table 33

monohaploid: a haploid cell or individual possessing only one chromosome set in the nucleus gene cyto

monohybrid: a cross between two individuals that are identically heterozygous for the alleles of one particular gene (i.e., Aa × Aa) gene

monohybrid heterosis >>> superdominance

monohybrid segregation: a segregation pattern according to a monogenic inheritance gene >>> Table 2

monoisodisomic: a cell or individual showing monosomy for one chromosome but an isochromosome for one of the arms of the missing chromosome cyto >>> Figure 37

monoisosomic: a cell or individual showing nullisomy of one chromosome but having an isochromosome for one arm of the missing chromosome pair cyto >>> Figure 37

monophyletic: a group of species that share a common ancestry, being derived from a single interbreeding population bot evol

monophyllous: showing one leaf bot

monoploid: having the basic chromosome number in a polyploid series cyto

monoplontic: it refers to a haploid individual or monoploid phase of the life cycle bot

monosome: a chromosome that lacks a homologue in a diploid organism cyto

monosomic: a genome that is basically diploid but that has only one copy of one particular chromosome type, so that its chromosome number is 2n – 1 cyto gene >>> Figure 37

monosomic analysis: a common method for gene mapping (e.g., in hexaploid wheat); when genes determining phenotypes of interest for which an aneuploid series is not available, crosses can be made to a monosomic series in a variety with a contrasting phenotypic pattern; the monosomics are used as female parents in order to ensure the majority of progeny (~ 72 %; the transmission of n – 1 gametes is about 75 % by the egg cell, but only about 4 % by the pollen) will be become monosomic; if the gene involved is both recessive and hemizygous-effective (an uncommon situation), direct phenotypic observations on F1 monosomic progenies enable the researcher to locate the gene on a particular chromosome; only monosomic individuals in the critical cross will exhibit the phenotype, whereas disomic sibs and monosomic (or disomic) progenies from all other crosses will display the dominant phenotype; if the plants of the monosomic series carry the dominant allele of a gene of interest, monosomic individuals in the critical cross exhibit the recessive phenotype, whereas disomic sibs display the dominant phenotype gene >>> aneuploid >>> Figure 37 >>> Table 23

monosomy >>> monosomic

monospermic >>> monospermous

monospermous: bearing one seed bot

monostand: sometimes it refers to a grass community composed of only one cultivar agr

monotelic: a mitotic chromosome with one oriented and one unoriented centromere cyto >>> centromere

monotelocentric: a cell or individual lacking one chromosome pair but showing one telocentric chromosome for one arm of the two missing homologues cyto >>> Figure 37

monotelodisomic: a cell or individual lacking one chromosome pair but showing two homologous telocentric chromosomes for one arm of the two missing homologues cyto >>> Figure 37

monotelomonoisosomic: a cell or individual lacking one chromosome pair but showing a telocentric chromosome for one arm of the missing homologous pair and an isochromosome for the other arm cyto >>> Figure 37

monotelotrisomic: a cell or individual showing an additional telocentric chromosome to a certain pair of chromosomes cyto >>> Figure 37

mordant >>> mordanting

mordanting: in a broad sense, to produce surface conditions by metal ions in the fixed structures that will enable them to hold the particular stains intended for making them visible cyto

MORGAN unit, morgan (M): a unit of relative distance between genes on a chromosome; one morgan (1 M) represents a crossing-over value of 100 %; a crossing-over value of 10 % is a decimorgan (dM); 1 % is a centimorgan (cM) gene

morphogenesis: the developmental processes leading to the characteristic mature form of a plant or parts of it phys

morphosis: a modification of the morphogenesis of an individual caused by environmental changes phys

morphotype >>> habit(us)

mortality: the relative frequency of deaths in a specific population (i.e., death rate) bio

mosaic: a pattern of disease symptoms displaying mixed green and lighter colored patches phyt

mosaicism: intraindividual variation of chromosome numbers or chromosome structure, usually in different tissues cyto

mother cell: special cells in the anther and ovule that give rise to pollen or egg cells bot

mother plant: the female ancestor of a hybrid and/or hybrid progeny; in horticulture, a mature plant from which cuttings are taken meth agr gene hort >>> donor plant

motif: a characteristic stretch of amino acids in a protein sequence which is responsible for a biochemical function, e.g. the active site of an enzyme biot

mould >>> mold

mound layering: a method of propagation whereby a branch or stem is scored and then brought into contact with the soil to spur rooting meth hort

MP-PCR >>> microsatellite-primed PCR

mRNA >>> messenger RNA

MS medium: in vitro culture medium named after the description by MURASHIGE and SKOOG biot

mtDNA: an abbreviation for mitochondrial DNA gene

mucilage: the gummy, sticky complex carbohydrate (consisting principally of polyuronides and galacturonides that chemically resemble the pectic compounds and hemicellulose) substances that cover the seeds, the root tip, bark, or stems of some plants bot

mugeinic acid: a chelating agent; it plays an important role in the uptake of heavy metal ions from the soil when it is exudated by roots of some gramineous plants (e.g., of rye) chem phys >>> chelate

mulch: a crumbly intimate mixture of organic and mineral material formed mainly by worms agr

mule: a plant hybrid that is self-sterile and usually cross-sterile due to infertile pollen or undeveloped pistils gene

multidimensional scaling (MDS): a multivariate method of showing similarities and/or dissimilarities of empirical data (e.g., genotypes) within an n-dimensional euclidic space (e.g., n = 2 or 3) in which the distances between the objects are as best as possible arranged according to the distances of the data matrix meth stat

multifactorial >>> polygenicmultigene family >>> multigene variety

multigene variety: a variety that carries a number of specific genes governing resistance to a particular pathogen phyt

multigenic: a trait that is controlled by many genes, as opposed to monogenic gene >>> polygenic

multigerm: an aggregate fruit containing several ovules bot >>> monogerm(ous)

multihybrid: an individual that is heterozygous for more than one gene gene

multiline: a cultivar or variety that is composed by many more or less defined lines seed >>> multiline variety

multiline variety: a composite (blended) population of several genetically related lines of a self-pollinated crop, but bearing different genes (e.g., for resistance to pathogens) seed

multilineal variety >>> multiline variety

multilocation testing: a testing of breeder’s strains and varieties on several geographically different sites in order to estimate the adaptive environmental response and/or performance stability meth

multi-locus probe: a DNA probe that hybridizes to a number of different sites in the genome of an organism biot

multinucleate: describes cells that have more than one nucleus bot

multiple alleles: the existence of several known allelic forms of a gene gene >>> allelism

multiple cropping: the growing of more than one crop on the same field in one year agr

multiple fruit: developed from a cluster of flowers on a common base bot

multiple genes: two or more genes at different loci that produce complementary or cumulative effects on a single, quantitative genetic trait gene >>> polygenes

multiple lattice design(s): it is often applied to test a large number of entries that are to be directly compared for selection; comparison among entries from different lattices is accommodated by the use of checks; while this design has some practical merits, it is statistically expected to be less efficient than alternative designs for a large number of entries; the comparison for a number of settings by using single large alpha-design shows that the efficiency gain in terms of sample size or variance may be appreciable; therefore, plant breeders should seriously consider using alpha-designs in place of multiple lattices stat meth

multiplication: the increase in number of individuals produced from seed or by vegetative means meth

multiply >>> multiplication

multitude of genes >>> polygenes

multiple population breeding system: the breeding population is subdivided in several smaller subpopulations that are bred for different objectives, e.g., different areas meth

multiplication: the increase in number of individuals produced from seed or by vegetative means meth

multiplication population: subpopulations of the general breeding population purposefully selected for different sets of traits or deployment destinations meth

multiply >>> multiplication

multitude of genes >>> polygenes

multivalent: designating and association of more than two chromosomes whose homologous regions are synapsed by pairs (e.g., in autopolyploids or in translocation heterozygotes) cyto >>> Figure 15

multivar >>> cultivar mixture

mummy: a dried, shriveled fruit or seed colonized by a fungus or parasite phyt

mutability: the ability of a gene to undergo mutation gene

mutable genes: a class of genes that frequently spontaneously mutate gene

mutable site >>> mutational site

mutagen: an agent that increases the mutation rate within an organism or cell; for example, X-rays, gamma-rays, neutrons, or chemicals (base analogues, such as 5-bromo uracil, 5-bromo deoxyuridine, 2-amino purine, 8-ethoxy caffeine, 1.3.7.9.-tetramethyl-uric acid, maleic hydrazide; antibiotics, such as azaserine, mitomycin C, streptomycin, streptonigrin, actinomycin D; alkylating agents, such as sulfur mustards [ethyl-2-chloroethyl sulfide], nitrogen mustards [2-chloroethyl-dimethyl amine], epoxides [ethylene oxide], ethyleneimines, sulfates, sulfonates, diazoalkanes, nitroso compounds [N-ethyl-N-nitroso urea]; azide [sodium azide]; hydroxylamine; nitrous acid; acridines [hydrocyclic dyes], such as acridine orange) gene

mutagenesis: the process leading to a mutant genotype gene

mutagenic: substances and circumstances inducing mutants gene

mutagenic agent >>> mutagen

mutagenicity: the potential of agents and circumstances to induce mutations gene

mutagenicity testing: the assessment of chemical or physical agents for mutagenicity gene meth

mutagenize: treatments that result in mutations meth

mutagenized: cells or individuals that were treated with mutagens gene

mutant: a plant bearing a mutant gene that expresses itself in the phenotype gene >>> Table 35

mutant site: a site on a chromosome at which a mutation can occur or has occurred gene

mutant strain: a strain of cells or individuals that, by one or more mutations, is differentiated from the original strain gene

mutation: a change in the structure or amount of the genetic material of an organism; in cytogenetics, a gene or a chromosome set that has undergone a structural change gene >>> unique event polymorphisms >>> Table 35

mutational hot spot: a site within a gene or genome that frequently mutates gene

mutational site: the more or less defined position along a gene at which mutations occur gene

mutation breeding: to experimentally introduce or remove a character from a cell or organism by exposure to mutagenic agents followed by screening for the desired attribute; it also refers to several techniques, involving induced mutations, that were utilized (mainly in the 1960s and 1970s) to introduce desirable genes into the plants (e.g., resistance to plant diseases, increased yield, improvements in composition); usually seeds or pollen were soaked in mutation-causing chemicals (mutagens) or via bombardment treated with ionizing radiation followed by screening of the resultant plants and selection of the particular mutation (beneficial trait) meth >>> Figure 1 >>> Table 35

mutation map: the frequency of mutations recorded along of chromosomes, represented as a diagrammatic drawing gene

mutation pressure: the continued production of an allele by mutations evol

mutation rate: the number of mutation events per gene and per unit of time (e.g., per cell generation) gene

mutator gene: a gene that may increase the spontaneous mutation rate gene

muton: the smallest unit of DNA in which a change can result in a mutation (i.e., the single nucleotide) gene

mutually orthogonal Latin square(s) - paarweise orthogonale lateinische Quadrate n pl: a set of >>> Latin squares, any two of which are orthogonal (syn pairwise orthogonal Latin squares) stat

mycelium (mycelia pl): a mass of hyphae that form the body of a fungus bot

mycobacterium (mycobacteria pl): any of several rod-shaped aerobic bacteria of the genus Mycobacterium bot

mycology: the science of fungi; the study of mushrooms bot

mycoplasma: the smallest free-living microorganism; it lacks a rigid cell wall and is therefore pleomorphic (polymorphic); mycoplasmas cause many diseases in plants; many formerly attributed to viruses are now known to be caused by mycoplasmas phyt

mycor(r)hiza: a close physical association between a fungus and the roots (or seedlings) of a plant from which both fungus and plant appear to benefit bot

mycotoxin(s): toxic substances produced by fungi or molds on agricultural crops phys chem phyt

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