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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

R1, R2, R3, etc.: the first, second, third, etc. generation following any type of irradiation in mutation breeding meth

RABL configuration: in plants and insects, it refers to chromosomes that are spatially organized within the nucleus, with centromeres clustered on the nuclear membrane at one pole and telomeres attached to the nuclear membrane of the other hemisphere cyto

race: a genetically and, as a general rule, geographically distinct interbreeding division of a species; in other contexts, a population or group of populations distinguishable from other such populations of the same species by the frequencies of genes, chromosomal rearrangements, or hereditary phenotypic characteristics; a race that has received a taxonomic name is a subspecies tax

RACE: rapid amplification of cDNA ends biot

raceme: an inflorescence in which the main axis continues to grow, producing flowers laterally, such that the youngest ones are apical or at the center bot

racemose: an indeterminate, unbranched inflorescence in which the flowers are borne on pedicels of about equal length, along an elongated axis bot

race-nonspecific type: host-plant resistance that is operational against all races of a pathogen species; it is variable, sensitive to environmental changes, and usually polygenetically controlled phyt

race-specific resistance: it is (individually) determined by single or very few genes in the plant - the specific resistance genes - and these are most usually effective against a limit proportion of the pathogen population; synonyms: vertical and qualitative resistance; the proportion of the pathogen population capable of causing disease on a resistant host is termed virulent on the host; the portion incapable of causing disease as avirulent on that host; correspondingly, the host is susceptible or resistant and the interaction compatible or incompatible, respectively; where the inheritance of virulence/avirulence has been studied, it is  generally found that a specific avirulence gene in the pathogen corresponds to specific resistance gene in the plant; this relationship is termed the gene-for-gene-hypothesis  phyt

race-specific type: host-plant resistance that is operational against one or a few races of a pathogen species; generally produces an immune or hypersensitive reaction and is controlled by one or a few genes phyt

rachilla: the spikelet axis; it is also applied to the segment of the rachilla that remains attached to the oat grain bot

rachis: the main axis of the ear and of the panicle of grasses bot

rad: an abbreviation for “radiation absorbed dose;” a measure of the amount of any ionizing radiation that is absorbed by the tissue; one rad is equivalent to 100 ergs of energy absorbed per gram tissue phy meth >>> radioactive

radiation absorbed dose >>> rad

radicle: the root of the embryo, which develops into the primary root of the seedling bot

radicule >>> radicle


radioactive: a substance when a constituent chemical element is undergoing the process of changing into another element through the emission of radiant energy; radioactivity is used as a tool in research to tag or trace the movement of compounds; the presence of a compound containing a radioactive element is revealed by instruments that measure the radiant energy emitted or by radio-sensitive films phy meth

radioactive tracer >>> isotopic tracer

radiocarbon dating syn 14C dating: a dating method for organic material that is applicable to about the last 70,000 years; it relies on the assumed constancy over time of atmospheric 14C:12C ratios and the known rate of decay of radioactive carbon, of which half is lost in a period of about every 5.730 years meth

raffinose: the raffinose family of oligosaccharides; it is believed to play an important role in the resistance of plants to environmental stress by protecting membrane-bound proteins; it is relevant when seeds mature because they rapidly lose moisture as they dry out phys


rain forest: a tropical forest of tall, densely growing, broad-leaved evergreen trees in an area of high annual rainfall eco

rain gauge: an instrument for measuring rainfall prep

ramet: an individual that belongs to a clone bot >>> cutting

ramification: the act or process of ramifying (i.e., the repeated division of branches into secondary branches) bot

ramify >>> ramification

random amplified polymorphic DNA (RAPD) technique: a comparative study (among individuals, populations, or species) of the DNA fragment length produced in controlled DNA synthesis reactions started with short sequences of DNA (primers); as a genetic mapping methodology, it utilizes as its basis the fact that specific DNA sequences (polymorphic DNA) are repeated (i.e., appear in sequence) with a gene of interest; thus, the polymorphic DNA sequences are linked to that specific gene; their linked presence serves to facilitate genetic mapping within a genome biot meth

random effects: effects of a treatment in an experiment in which the treatments are considered in relation to a whole range of possible treatment effects stat

random genetic drift: variation in gene frequency from one generation to another due to chance fluctuations gene evol

random lines >>> isogenic lines

random mating: for a given population, where an individual of one sex has an equal probability of mating with any individual of the opposite sex, or insofar as the genotypes with respect to given genes are concerned gene

random sample: a sample of a population selected so that all items in the population are equally likely to be included in the sample stat

random sampling: a sample drawn from a population in such a way that every individual of the population has an equal chance of appearing in the sample; it ensures that the sample is representative and provides the necessary basis for virtually all forms of inference from sample to population, including the informal inference, which is characteristic of rerandomization statistics stat

randomization: the process of making assignments at random; in field trials, randomization of entries is required to obtain a valid estimate of experimental error; each entry must have an equal chance of being assigned to any plot in a replication and an independent randomization is required for each replication stat meth >>> Table 25


randomized block: the entries to be tested are assigned at random to the plots within the block stat meth >>> Table 25


randomized block design: a randomized block analysis of variance design (e.g., one-way blocked ANOVA) is created by first grouping the experimental subjects into blocks; the subjects in each block are as similar as possible (e.g., littermates); there are as many subjects in each block as there are levels of the factor of interest; randomly assigning a different level of the factor to each member of the block, such that each level occurs once and only once per block; the blocks are assumed not to interact with the factor stat >>> Table 25 >>> randomized block >>> randomized complete block


randomized complete block (RCB): each block contains a plot for each candidate to be tested; in that case the classification of the data according to the blocks and the classification according the candidates are orthogonal stat meth >>> Table 25


range of reaction: the range of all possible phenotypes that may develop by interaction with various environments from a given genotype; it is also called “norm of reaction” gene

range pole >>> landmark

RAPD >>> random amplified polymorphic DNA technique

raphanobrassica: an intergeneric hybrid between Raphanus and Brassica species; a first hybrid was already reported in 1826; about 100 years later KARPECHENKO produced a hybrid between Raphanus sativus (2n = 2x = 18, RR) x Brassica oleracea (2n = 2x = 18, CC) >>> 2n = 4x = 36, RRCC

raphe: a ridge, sometimes visible on the seed surface, which is the axis along which the ovule stalk joins the ovule bot

rapid multiplication: techniques in order to accelerate production of a new plant cultivars, e.g., green >>> cuttings of a >>> potato clone can be rooted in a mist propagator and, when planted out, the cuttings will themselves produce more cuttings meth

rate of response to selection >>> selection progress

ratooning: a sprout or shoot from the root of a plant (e.g., in sugarcane) after it has been cropped bot

ratooning crop: obtaining a second crop from the same plant (e.g., in sugarcane) agr

ray: a pedicel in an umbellate inflorescence bot

ray flower: a flower head with outer ray flowers forming petallike structures surrounding the inner disc flowers (e.g., in the Asteraceae or in sunflower) bot

RCB >>> randomized complete block

rDNA >>> ribosomal DNA

rDNA-ITS >>> ribosomal DNA internal transcribed spacers

reading frame: the mechanism that moves a ribosome, one codon at a time, from a designated start sequence during genetic translation; a shift in the reading frame by any number of nucleotides other than three or multiples of three will cause an entirely new sequence of codons gene

reading mistake: the placement of an incorrect amino acid into a polypeptide chain during protein synthesis gene >>> reading frame

reagent: a substance that, because of the reactions it causes, is used in analysis and synthesis meth chem

realized genetic gain: it refers to the observed difference between the mean phenotypic value of the offspring of the selected parents and the phenotypic value of the parental generation before selection meth

realized heritability: it refers to heritability measured by a response to selection; it is the ratio of the single-generation progress of selection to the selection differential of the parents stat

reaper: a machine for cutting standing grain agr

reaper-binder: an implement that cuts and ties hay into bundles agr

rearrangement: all chromosome mutations that result in modified karyotypes cyto >>> translocation >>> interchange >>> chromosome mutation

reassociation >>> anneal

rebloom: in ornamental plants, a valuable characteristic in which a plant blooms at its normal period and then, after a period of rest, produces a second set of flowers hort

recalcitrant seed: seed that does not survive drying and freezing; in particular, seed that cannot withstand either drying or temperatures of less than +10°C and, therefore, cannot be stored for long periods, as compared to orthodox seeds seed

receptacle: the part of the stem from which all parts of the flower arise; in Compositae, the flattened tip of the stem that bears the bracts and florets bot

receptaculum >>> receptacle

receptor site: in molecular genetics, a set of reactive chemical groups in the cell wall of a bacterium that are complementary to a similar set in the tailpiece of bacteriophage gene

recessive: a gene and/or allele whose phenotypic effect is expressed in the homozygous state but masked in the presence of the dominant allele; usually the dominant gene and/or allele produces a functional product whereas the recessive gene and/or allele does not; both one and two doses per nucleus of the dominant allele may lead to expression of its phenotypes, whereas the recessive allele is observed only in the complete absence of the dominant allele gene >>> Table 6

recessive allele >>> recessive

recessive epistasis: the effect of a recessive allele of a gene suppressing the phenotype manifestation of another gene gene >>> Table 6

recessiveness >>> recessive

recipient: one that receives; receiver gene meth

recipient cell >>> recipient

reciprocal cross: one of a pair of crosses in which the two opposite mating types are each coupled with each of two different genotypes and mated with the reciprocal combination; for example, male of genotype A x female of genotype B (first cross) and male of genotype B x female of genotype A (reciprocal cross); such crosses are used (1) to detect sex linkage, (2) maternal inheritance, or (3) cytoplasmic inheritance meth

reciprocal full-sib selection: a method of interpopulation improvement for species in which the commercial product is hybrid seed; a cycle of selection is completed in the fewest number of seasons by use of plants from which both selfed and hybrid seed can be obtained meth

reciprocal genes: nonallelic genes that reciprocate or complement one another gene

reciprocal half-sib selection >>> reciprocal recurrent selection

reciprocal recurrent selection: a breeding method used to achieve an accumulation of genes that are valuable for specific traits but also for combining ability; in practice, two populations form the basis of selection; reciprocally, one population serves as a tester for the investigation of the selections deriving from the other population; from the first population, usually a greater number of plants is selfed and at the same time crossed with several plants of the second population; the same procedure is realized with the second population; during the second year, the progenies of the test-crosses are subjected to performance trials; the progenies of the cross of one female parent, derived from population 1, are combined with several male parents from population 2; based on the performance testing, progenies from selfed seed, produced by best plants, are grown during the third year; in the same year, the best progenies of selfings are crossed in many combinations; seeds obtained from those crosses form the improved populations for growing during the fourth year; within such populations individual plants may be selfed again and crossed for utilization in a new cycle meth >>> recurrent selection >>> Figure 21

reciprocal translocation: a translocation that involves an exchange of chromosomes segments between two nonhomologous chromosomes cyto >>> translocation >>> Robertsonian translocation >>> chromosome mutation

recognition sequence (site): a nucleotide sequence composed typically of 4, 6, or 8 nucleotides; it is recognized by a restriction endonuclease; so-called type II enzymes cut (and their corresponding modification enzymes methylate) within or very near the recognition sequence biot gene

recombinant: an individual or cell with a genotype produced by recombination (i.e., with combinations of genes other than those carried in the parents); they result from independent assortment or crossing over gene

recombinant DNA molecule: DNA molecule created by ligating together two not normally contiguous DNA molecules biot

recombinant DNA technology: DNA molecules constructed by joining, outside the cell, natural or synthetic DNA segments to DNA molecules capable of replication in living cells biot >>> biotechnology

recombinant inbred line(s) (RILs): a population of fully homozygous individuals that is obtained through the repeated selfing of an F 1 hybrid, and that comprises 50 % of each parental genome in different combinations; they derive from multiple inbred strains (either by selfing or by full-sib mating) and can serve as a powerful resource for the genetic dissection of complex traits; however, the use of such multiple-strain requires a detailed knowledge of the haplotype structure in such lines gene meth stat biot

recombinant protein: a protein synthesized from a cloned gene biot

recombinant type: an association of genetic markers, found among the progeny of a cross, that is different from any association of markers present in the parents gene

recombination: the process whereby new combinations of parental characters may arise in the progeny, caused by exchange of genetic material of different parental lines gene >>> Figure 24 >>> Table 22

recombination counting and ordering method (RECORD): a method for the ordering of loci on genetic linkage maps; it minimizes the total number of recombination events; the search algorithm is a heuristic procedure, combining elements of branch-and-bound with local reshuffling; it does not require intensive calculations; the algorithm rapidly produces an optimal ordering as well as a series of near-optimal ones; the latter provides insight into the local certainty of ordering along the genetic map; compared to “JoinMap” RECORD is much faster and less sensitive to missing observations and scoring errors, since the optimization criterion is less dependent on the position of the erroneous markers; RECORD performs better in regions of the map with high marker density stat meth

recombination frequency: the number of recombinants divided by the total number of progeny, expressed as a percentage or fraction; such frequencies indicate relative distances between loci on a genetic map gene >>> mapping >>> Table 22

recombination nodule: swellings along DNA strands and associated proteins during prophase pairing of chromosomes; the nodules can be identified under the electron microscope; it is suggested that recombination nodules are the sites of genetic crossing over cyto

recombination system: all factors that mediate and control the process of genetic recombination gene

recombination unit >>> MORGAN unit

recon: the smallest unit of DNA capable of recombination gene

RECORD >>> recombination counting and ordering method

recurrent full-sib selection: a method of intrapopulation improvement that involves the testing of paired-plant crosses; it is the only method of recurrent selection in which the seeds from two individuals, rather than one, are used for testing and to form the new population meth

recurrent half-sib selection - wiederholte Halbgeschwisterauslese f: a method of intrapopulation improvement that includes the evaluation of individuals through the use of their half-sib progeny; the general procedure for a cycle of selection is (1) to cross the plants being evaluated to a common tester, (2) evaluate the half-sib progeny from each plant, and (3) intercross the elected individuals to form a new population meth

recurrent mass selection - wiederholte Massenauslese f: a breeding method designed to increase the levels of desirable qualities, which are quantitative variables, by changing the frequency of polygenes;in each screening generation, the best individuals are selected, and they become the parents of the next screening generation; the process is repeated for as many generations as necessary, but the rate of progress declines dramatically after a few generations meth

recurrent parent: the parent to which a hybrid is crossed in a backcross; it replaces the dragged alleles step by step with the alleles of the original variety meth

recurrent (backcross) parent >>> recurrent parent

recurrent reciprocal selection: a recurrent selection breeding system in which genetically different groups are maintained and, in each selection cycle, individuals are mated from the different groups to test for combining ability meth >>> recurrent selection >>> Figure 21

recurrent selection - wiederholte Auslese f: a method designed to concentrate favorable genes scattered among a number of individuals; it is performed by repeated selection in each generation among the progeny produced by matings inter se of the selected individuals of the previous generation; in practice, plants from a population are selfed and, after the yield of the selfed seeds, the progenies of the phenotypically best individuals are grown in the second year; the best progenies are then crossed in as many combinations as possible and the seeds received hereby are grown in the third year as a population; within the already improved population, selection and selfing can be carried out again; with this population a second cycle of recurrent selection can be started meth >>> facilitated recurrent selection >>> Figures 4, 20, 21

recurved: used to describe how the tips of some flower petals curl under hort

rediploidization: in anther culture, the haploidization of the genome by culturing pollen grains to haploid plantlets and its rediploidization after spontaneous or induced doubling of the chromosome set biot >>> Figures 17, 26 >>> Table 7

reducers: one of three basic types of organisms called producers, reducers, and consumers; reducers break down the organic chemicals of dead organisms, and they make these nutrients available for re-use by other organisms evol

reductase: an enzyme responsible for reduction in an oxidation-reduction reaction chem phys

reduction division: the two nuclear divisions in meiosis that produce daughter nuclei, each of which has half as many chromosomes as the parental nucleus bot >>> meiosis

reductional division >>> reduction division >>> meiosis

redundant DNA: DNA that does not appear to be genetically active and hence is not translated or transcribed; it often consists of repeated sequences gene

redundant gene: a gene that is present in many functional copies, so that one copy can complement the loss of another copy gene

re-encounter parasite: it happens when a >>> crop >>> host is taken to another part of the world, some of its parasites may be left behind in the area of origin, e.g., tropical rust, when >>> maize was taken from the New World to Africa; if the parasite arrives in the new area at a later date, it is described as a re-encounter parasite, usually very damaging because the crop host tends to lose >>> horizontal resistance during the absence of that parasite phyt

referee plant breeder: a plant breeder recognized by an official organization  to make decisions on varietal identification of crops agr seed

regeneration cut: a timber harvest designed to promote and enhance natural establishment of trees; even-aged stands are perpetuated by seed tree, shelterwood, and clearcuts; >>> uneven-aged stands are perpetuated by selection of individual or small groups of trees fore

release: to free trees from competition by cutting or otherwise removing or killing nearby vegetation and branches; usually applied to young stands fore

REML >>> restricted maximum likelihood


.... more on CD

repair grafting >>> bridge grafting

repeated block(s): an incidence structure of points and blocks has repeated blocks if there are two blocks incident with exactly the same points stat

.... more on CD

replicate estimate: an estimate of the population quantity based on the replicate subsample using the same estimation methods used to compute the full sample estimate stat

replicate sample: one of a set of subsamples, each obtained by deleting a number of observations in the original sample for the purpose of computing the appropriate variance based on the complex design of the survey stat

replication error: any modification that prevents or disturbs the DNA replication process gene

replication number: the replication number of a treatment in a >>> block design is the number of times the treatment occurs in the design; in the case of a binary design, this is equal to the number of blocks in which the treatment occurs; in a resolvable design, it is equal to the number of replicates or parallel classes in a resolution stat

replication unit >>> replicon

replicon: a structural gene that controls the synthesis of a specific initiator along with a replicator locus upon which the corresponding initiator acts gene

reporter gene: in DNA or gene transfer experiments, the linkage of a gene that (transient) expression can easily be detected with a target DNA sequence or gene biot

repressor: a protein produced by a regulatory gene that inhibits the activity of an operator gene, and hence switches off an operon gene

repressor gene >>> repressor

reproduce: to create another individual of the parental type that will in turn produce another meth >>> reproduction >>> Table 35

reproducible >>> reproduction

reproduction: the process of forming new individuals of a species by sexual or asexual ways bot gene; in forestry, the process by which the forest is replaced or renewed, either artificial reproduction, by means of seeding or planting or natural reproduction, from natural seeding or sprouting fore >>> Table 35

reproductive isolating mechanism: any biological property of an organism that interferes with its interbreeding with organisms of other species gene eco >>> Table 35

reproductive isolation: the absence of interbreeding between members of different species eco

reproductive meristem >>> generative meristem

reproductive organ: usually, it refers to the sexual organ bot

repulsion: the linkage phase of a double heterozygote for two linked gene pairs, which has received one dominant factor from each parent and the alternative recessive factor from each parent (e.g., for genes and/or alleles A, a and B, b the repulsion heterozygote receives Ab from one parent and aB from the other, where A and B are dominant, and a and b are recessive) gene

reselection >>> backward selection

residue seed method >>> method of overstored seeds

resilience: the ability of a population to persist in a given environment despite disturbance or reduced population size; based upon the ability of individuals within the population to survive (fitness) and reproduce (fecundity) in a changed environment gene eco

resin: an exudate of tree wood or bark, liquid but becoming solid on exposure to air, consisting of a complex of terpenes and similar compounds bot

resistance: inherent capacity of a host plant to prevent or retard the development of an infectious disease; there are different types of resistance: (1) hypersensitivity (infection by the pathogen is prevented by the plant), (2) specific resistance (specific races of the pathogen cannot infect the plant), (3) nonuniform resistance (the host prevents the establishment of certain races), (4) major gene resistance (races of the pathogen are controlled by major genes in the host), (5) vertical resistance (host resistance controls one or a certain number of races), (6) field resistance (severe injury in the laboratory, but resistance under normal field conditions), (7) general resistance (the host is able to resist the development of all races of the pathogen), (8) nonspecific resistance (host resistance is not limited to specific races of the pathogen), (9) uniform resistance (host resistance is comparable for all races of the pathogen, rather than being good for some races), (10) minor gene resistance (host resistance is controlled by a number of genes with small effects), (11) horizontal resistance (variation in host resistance is primarily due to differences between varieties and between isolates, rather than to specific variety x isolate interactions) phyt >>> biological control >>> Table 33

resistance breeding: special crossing and selection methods in order to improve the inherent capacity of a crop plant to prevent or retard the development of an infectious disease phyt meth >>> resistance >>> Table 33

resistant >>> resistance

resistant rootstock(s) - resistente Unterlage f: some vegetatively propagated tree crops have superb agricultural or horticultural characteristics but are susceptible to various soil-borne parasites; they are then grafted on to resistant rootstocks, e.g., the grafting of classic, European, wine grapes on to American rootstocks to control >>> Phylloxera; many fruit trees (e.g., stone and pome fruits, citrus) and other high-yielding clones (e.g., rubber) are grafted on to resistant rootstocks for this reason phyt hort meth

resolution: the smallest distance by which two objects can be separated and still be resolved as separate objects micr

resolving power >>> resolution

respiration: oxidative reactions in cellular metabolism involving the sequential degradation of food substances and the use of molecular oxygen as a final hydrogen acceptor phys

responsible plant breeder: the plant breeder or breeding organization that is officially recognized as the maintainer of breeder seed reference samples and production for a variety seed

rest: a condition of a plant in which growth cannot occur, even though temperatures and other environmental factors are favorable for growth phys >>> dormancy

rest period >>> rest >>> dormancy

resting bud >>> hibernaculum

resting spore: a spore germinating after a resting period (frequently after overwintering), as does an oospore or a teliospore phyt

restitution nucleus: a nucleus with an unreduced chromosome number cyto

restorer: an inbred line that permits restoration of fertility to the progeny of male sterile lines to which it is crossed seed >>> Figure 23

restorer gene: a gene and/or allele that is able to restore fertility of a sterile genotype; while genes for sterility frequently belong to the mitochondrial genome (i.e., cytoplasmic), the restorer genes are very often found to belong to the nuclear complement; they are used in hybrid variety production gene >>> Figure 2

restorer line (R line): a pollen parent line; it contains the restorer gene or genes, which restores cytoplasmic male sterile plants to pollen fertility; it is crossed with an A line in the production of hybrid seeds seed >>> Figures 2, 23

restoring gene >>> restorer gene

restricted maximum likelihood (REML): a multi-trait (co)variance estimation stat

restriction analysis: determination of the number and size of the DNA fragments produced when a particular DNA molecule is cut with restriction endonucleases biot >>> restriction enzyme

restriction endonuclease >>> restriction enzyme

restriction enzyme: an enzyme that functions in a bacterial modification-restriction system and recognizes specific nucleotide sequences and breaks the DNA chain at these sites; there is a great number of them, each with different recognition and/or cutting sites; they are intensively used as a tool in molecular genetics and also in producing chromosomal banding patterns in cytogenetics gene >>> restriction analysis

restriction-enzyme-mediated integration (REMI): a method of transformation that generates tagged mutations biot

restriction fragment length polymorphism (RFLP): a comparative study (in individuals, populations, or species) of the DNA fragment lengths produced by particular restriction enzymes; by using a DNA hybridization technique, restriction fragments can be identified if they are complementary to a specific DNA probe; each mutation that produces or eliminates a restriction site in a homologous region leads to a change of length of the restriction fragment, which has to be detected; it is used to infer genomic relationships; RFLPs represent an important tool in detecting variability; they are free of secondary effects due to pleiotropic action and they are frequently associated with the segregation of alleles affecting morpho-physiological traits; the advantages are as follows: (1) they are everywhere present in the genome and in living organisms, (2) they show Mendelian inheritance, (3) they show codominant expression, (4) they have no pleiotropic effects, (5) they are independent of environmental effects, (6) they are available at each developmental and/or physiological stage, (7) different loci within the genome can be identified by one DNA probe, (8) heterologous genes may also be used as probes, (9) any number of DNA probes can be established, (10) probes are available for coding and silent genes (DNA sequences), (11) probes show also the variability of flanking DNA sequences, and (12) several traits can be screened in the same experimental sample meth >>> Table 29

restriction map: representation of DNA with the position of restriction sites indicated gene >>> restriction analysis

restriction site: a certain nucleotide sequence within the double-stranded DNA; it is recognized by a restriction endonuclease; the enzyme cuts the double strand within the recognition sequence; the restriction sites are usually composed of four to six base pairs and are bilaterally symmetric; both strands are cut either on exactly opposite positions (blunt ends) or alternated ones (sticky ends); the type of cutting depends on the enzyme used gene

resynthesis: the artificial production of autopolyploids or allopolyploids of naturally occurring autopolyploid or allopolyploid plants by utilization of the presumable parental species (e.g., it was done in wheat and rapeseed) meth

retrotransposon: retrotransposons are a ubiquitous and major component of plant genomes; those with long terminal DNA repeats (LTRs, Ty1-copia-like family) are widely distributed over the chromosomes of many plant species gene


reverse genetics: using linkage analysis and polymorphic markers to isolate a disease gene in the absence of a known metabolic defect, then using the DNA sequence of the cloned gene to predict the amino acid sequence of its encoded protein; in general, a technology aiming at isolating mutants of a given sequence; it is also applied for identification of gene function gene biot

reverse mutation: the production by further mutation of a premutation gene from a mutant gene; it restores the ability of the gene to produce a functional protein; strictly, reversion is the correction of a mutation (i.e., it occurs at the same site) gene

reverse transcriptase: an enzyme from retroviruses for the synthesis of a DNA complementary to a RNA molecule (i.e., cDNA); it is used for (1) filling-in reactions, (2) for DNA sequencing, and (3) for cDNA synthesis biot

reversion >>> reverse mutation

revertant: an allele that undergoes reverse mutation or a plant bearing such an allele gene >>> reverse mutation

RFLP >>> restriction fragment length polymorphism

rheogameon: it refers to species composed of segments with marked morphological divergence but gene exchange takes place between them tax gene

rhizoid: it refers to hair-like filamentous anchorage or absorbing organ bot

rhizome: a horizontally creeping underground stem that bears roots and leaves and usually persists from season to season bot


rhizosphere: the soil near a living root agr

rhodanese: the enzyme is defined biochemically by its ability to transfer sulfur from thiosulfate to cyanide, yielding thiocyanate; it is found in plants, animals, and bacteria phys

Rht gene >>> short-straw mutant

rhytidome >>> bark

rhytmicity >>> periodicity

rib: a primary or prominent vein of a leaf bot

ribonuclease >>> RNase

ribonucleic acid (RNA): a polymer composed of nucleotides that contain the sugar ribose and one of the four bases adenine, cytosine, guanine, and uracil gene

ribonucleoprotein: a protein composed of pre-rRNAs and ribosomal as well as nonribosomal protein components; one of the nonribosomal proteins, the nucleolin, is considered to play a key role in regulation of rDNA transcription, perisomal synthesis, ribosomal assembly, and maturation phys

ribosomal DNA internal transcribed spacers (rDNA-ITS): a multigene family with nuclear copies in eukaryotes that are arranged in tandem arrays in nucleolar organizer regions (>>> NORs) generally at more than one chromosomal location; each unit within a single array consists of genes coding for small (18S) and large (28S) rRNA subunits; the 5.8 S nuclear rDNA gene lies embedded between these genes but separated by two internal transcribed spacers ITS1 and ITS2; for example, the copy numbers of 18S-5.8S-28S rRNA genes in diploid genomes of Quercus cerris, Q. ilex, Q. petraea, Q. pubescens and Q. robur are estimated to be in the number of 1300-4000; the small subunit is highly conserved and has been used for relationship between Archaebacteria and Eubacteria, while more conserved domains within the 28S region have been used to cover evolutionary time through the Paleozoic and Mesozoic eras; the faster evolving ITS regions has been employed for population and congeneric phylogenies; internal transcribed spacers represent bi-parental nuclear mode of inheritance through several loci with several alleles per locus, are co-dominant, exhibit high level of variability even within a single individual and composed of non-coding sequences biot

ribosomal RNA: the RNA molecules that are structural parts of ribosomes (i.e., 5S, 16S, and 23S RNAs in prokaryotes and 5S, 18S, and 28S RNAs in eukaryotes) gene

ribosome: one of the ribonucleoprotein particles, which are the sites of translation; it consists of two unequal units bound together by magnesium ions gene

riboswitch:a part of an >>> mRNA molecule that can directly bind a small target molecule, and whose binding of the target affects the gene's activity, an mRNA that contains a riboswitch is directly involved in regulating its own activity, in response to the concentrations of its target molecule; the discovery that modern organisms use >>> RNA to bind small molecules, and discriminate against closely related analogs, significantly expanded the known natural repertoire of RNA beyond its ability to code for proteins or to bind other RNA or protein macromolecules; most known riboswitches occur in bacteria, but functional riboswitches of one type (the TPP riboswitch) have been discovered in plants and certain fungi; the original definition of the term "riboswitch" specified that they directly sense small-molecule metabolite concentrations; although this definition remains in common use, sometimes a broader definition that includes other cis-regulatory RNAs is applied biot meth

rice-Azolla-fish culture: a farming system originally developed in China in which rice, Azolla and fish grow in the same field; Azolla serves as the feed for fish; this system improves both fish and rice yield agr

rice grassy stunt 1 and 2 virus: causal agents are rice grassy stunt virus 1 (RGSV1) and rice grassy stunt virus 2 (RGSV2); the symptoms of RGSV1 are severe stunting, excessive tillering, pale green to yellow and narrow leaves with small rusty spots; RGSV2 causes severe stunting, excessive tillering, yellow to orange and narrow leaves with small rusty spots phyt

rice hoja blanca disease: symptoms are cream colored to yellow spots, elongating and coalescing to form longitudinal yellowish green to pale green striations; streaks may coalesce to cover the whole leaf; brown and sterile glumes with typical "parrot beak" shape of deformation phyt

rice ragged stunt virus: causal agent is rice ragged stunt virus (RRSV); symptoms are plants are stunted but remain dark green; leaves are ragged and twisted; vein swelling on leaf collar, leaf blades and leaf sheaths phyt

rice tungro virus: causal agent is rice tungro bacilliform virus (RTBV) and rice tungro spherical virus (RTSV); the disease is transmitted by the green leafhopper Nephotettix spp.; symptoms are yellow-to-yellow orange leaves, stunting and slightly reduced tillering phyt

rice whorl maggot disease: causal agentis Hydrellia philippina; symptoms are leaf margin feeding causes conspicuous damage and sometimes stunting of plants phyt

ridge tillage: a type of soil conserving tillage in which the soil is formed into ridges and the seeds are planted on the tops of the ridges; the soil and the crop residue between the rows remain largely undisturbed; the practice offers opportunities to reduce crop production costs by banding fertilizers and pesticides and reducing the need for field trips agr

rifamycin(s): a group of antibiotics that inhibit initiation of transcription in bacteria biot phys

rind: a thick and firm outer coat or covering (e.g., in watermelon, orange, etc. or the bark of a tree) bot

ring bivalent: an association of two chromosomes with terminal chiasmata on both arms cyto >>> Figure 15

ring chromosome: a (sometimes aberrant) chromosome with no ends (e.g., the chromosome of bacteria); an isochromosome may also form a ring in MI of meiosis cyto

RINGER solution: a physiological saline containing sodium, potassium, and calcium chlorides used in physiological experiments for temporarily maintaining cells or organs alive in vitro phys

ripe >>> mature

RNA >>> ribonucleic acid

RNAi >>> RNA interference

RNA interference (RNAi): the use of double stranded RNA to interfere with gene expression; RNAi is usually mediated by approximately 21-nt small interfering RNAs meth biot

RNA interference (RNAi) technology: a mechanism that inhibits gene expression by inhibiting >>> translation, causing the degradation of specific RNA molecules or hindering the >>> transcription of specific genes; RNAi targets include RNA from viruses and transposons and also plays a role in regulating development and genome maintenance; small interfering RNA strands are key to the RNAi process, and have complementary nucleotide sequences to the targeted RNA strand; specific RNAi pathway proteins are guided by the small interfering RNA to the targeted messenger RNA, where they "cleave" the target, breaking it down into smaller portions that can no longer be translated into protein; the RNAi pathway is initiated by the enzyme dicer, which cleaves long, double-stranded RNA molecules into short fragments of 20-25 base pairs; one of the two strands of each fragment, known as the guide strand, is then incorporated into the RNA-induced silencing complex and pairs with complementary sequences; the outcome of this recognition event is post-transcriptional >>> gene silencing biot meth

RNA transcriptase: the enzyme responsible for transcribing the information encoded in DNA into RNA; it is also called transcriptase or RNA polymerase biot

RNase: an enzyme hydrolyzing RNA gene

Robertsonian translocation: a chromosomal mutation due to centric fusion or centric fission (i.e., a reciprocal translocation with breakpoints within the centromeric regions); in wheat, Robertsonian translocations arise from centric misdivision of univalents at anaphase/telophase I, followed by segregation of the derived telocentric chromosomes to the same nucleus, and fusion of the broken ends during the ensuing interkinesis cyto >>> translocation

rod (rd): equals 5.03 m

rogue: to remove individuals that have an undesirable phenotype, or that have been shown through progeny tests to have a less desirable genotype from a seed orchard, seed production area, or nursery bed meth >>> genetic thinning

rolled paper toweling: adjusted filter paper or paper towels are used for this method in order to germinate seeds inside and/or between the layers of paper; after germination and growth the viability and/or germability are determined seed

roller: a device that compacts the soil to produce a firm seedbed, like a packer agr >>> packer

root: the lower part of a plant, usually underground, by which the plant is anchored and through which water and minerals enter the plant bot


root ball: the roots and soil or soil mix that they are growing in when lifted from the open ground hort

root cap: a cap of cells covering the apex of the growing point of a root and protecting it as it is forced through soil bot

root crop: a crop, such as beets, turnips, or sweet potatoes, grown for its large, edible roots agr

root culture: the in vitro growth of roots (e.g., root tips or root meristem on a synthetic medium) biot

root cuttings: root cuttings are made by cutting off pieces of root and planting them under suitable conditions; in this way some plants species or varieties can be easily propagated meth agr hort


root grafting: the process of grafting scions (shoots) directly on a small part of the root of some appropriate stock, the grafted root then being potted hort

root hair: a tabular outgrowth of an epidermal cell of a root, which functions to absorb water and nutrients from the soil bot

rooting: the natural or induced process of root formation phys bot

rooting compound: a powdery substance into which fresh cuttings are dipped before inserting in soil or medium, containing hormones, such as kinetins, to encourage root growth meth prep hort

root nodule: a small, gall-like growth on the roots of certain types of plants (legumes); the nodules develop as a result of infection of the root by bacteria bio agr

root pruning: cutting the roots of large plants, mainly trees and shrubs, to force more vigorous growth or to prepare the plant for transplantation or transportation meth hort

rootstock: synonymous with “rhizome”; in horticulture, the bottom or supporting root used to receive a scion in grafting hort >>> rhizome

rootstock variety: in horticulture, there are special (fruit) tree varieties (often of wild-type character) that serve as rootstock for graftings; usually they show good root formation, resistance traits, and compatibility with the scion hort

root sucker: a shoot arising adventitiously from a root of a plant; mostly at some distance from the main trunk bot

rosarium: since Roman times, a rose garden and breeding site of roses hort

rosel(l)ate >>> rosette

rosette: an arrangement of leaves radiating from a root crown near the earth bot

rosette plant >>> rosette

rosular >>> rosette

rot: to deteriorate, disintegrate, fall, or become weak due to decay agr

rotary hoe: an implement that breaks the soil with a circular motion agr

rotation >>> crop rotation

rotation age: the age at which the stand is considered ready for harvesting under the adopted plan of management fore

rotation of crops >>> crop rotation

rotenone: a natural >>> insecticide extracted from the roots of Derris elliptica of Southeast Asia, where it is used to control body lice, and from Lonchocarpus in South America; these plants are cultivated in a number of tropical countries and improved cultivars are available; no >>> resistance to rotenone has ever been known to develop in any species of insect phyt

rouge: a noun referring to an off-type plant; when used as a verb it refers to the act of removing, to uproot or destroy such plants that do not conform to a desired standard or are diseased seed

rouging: a manual removal of infected or inferior specimens from an otherwise healthy crop of plants seed

round-dance neighbor design: a >>> neighbor design in which blocks are complete (each treatment occurs once in each block) and have a circular structure so that each pair of elements occurs as neighbors in a circle exactly once stat

row-column design - zweifache Blockanlage mit vollständiger kreuzklassifizierter Blockstruktur f: an experimental design in which the set of plots has the structure of a rectangle, in which two plots may be in the same row, or in the same column, or neither stat

row-complete Latin square: a >>> Latin square is row-complete if each ordered pair of distinct symbols occurs precisely once in consecutive positions in a row of the square stat

row-quasi-complete Latin square: a >>> Latin square if each unordered pair of distinct symbols occurs precisely twice in consecutive positions in a row of the square stat

row spacing: the distance between rows of crop plants; it depends on needs for optimal plant growth, plant density, weed control, and harvest technology agr

rRNA >>> ribosomal RNA

rub >>> rubbing

rubbed seeds >>> rubbing

rubbing: smooth the surface of multigerm seed of sugarbeet seed

rubisco: a CO2-fixing enzyme; the key enzyme in photosynthesis; it is the most frequent protein on earth; it has a unique double function of being both a carboxylase and an oxygenase; when acting as an oxygenase, it catalyzes the light-dependent uptake of O2 and the formation of CO2 in a complicated process (photorespiration), which takes place concomitantly in three organelles—chloroplasts, peroxisomes, and mitochondria; there are projects to manipulate the enzyme in order to create an artificial plant that can contribute to reduction of CO2 content in the atmosphere (i.e., decreasing the so-called greenhouse effect) phys biot

ruderal plant: a plant that is associated with human dwellings or agriculture, or one that colonizes waste ground eco

rudiment >>> rudimentary

rudimentary: incompletely developed bot

run out: separation of nucleic acid or protein molecules by gel electrophoresis prep

runner: a procumbent shoot that takes root, forming a new plant that eventually is freed from connection with the parent by decay of the runner; it serves as a vegetative propagule (e.g., in strawberry) bot >>> stolon

rush >>> reed

russet: a brownish roughened area on the skin of fruits as a result of cork formation phyt

© by R. Schlegel 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014

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