Acronyms and Glossary of Rice Related Terminology Updated November 27, 2002

I Terms

I1, I2, I3, etc. Symbol used to designate the first, second, third inbred generations, etc.

ideotype. An ideal plant type used as a model for selective breeding to develop specific plant characteristics desired or required in particular ecosystems.

illite. A 2:1 layered clay in which a negative charge caused by ion substitution is neutralized by potassium ions.

imbibition. The process of absorbing or taking in water as in drinking.

immature grains. Grains with still greenish caryopsis or brown rice.

immobilization. The conversion of an element from inorganic form to organic form in microbial tissues so that the element is not readily available to plants.

immune. Completely resistant to pest or disease of the plant.

imperfect flower. Lacking a pistil or stamen.

impervious. Incapable of being penetrated. Resistant to penetration by fluids or by roots.

import permit. A document allowing a person to order and receive a thing from another country. Used in seed exchange.

improved cultivar. A rice variety that has been bred to increase production.

improved plant type. Specific morphological and physiological features of the rice plant that make it more efficient and higher yielding.

in situ. Latin: meaning, in the natural or original location.

in situ hybridization. A technique used for hybridization of cytological (chromosome) preparations with the labeled DNA probes. The method couples molecular biology, biochemistry, and cytology. Usually the expression of a gene (as RNA) or the location of target DNA (for example, in a chromosome) is detected by a molecular probe. The probe can be labeled by a variety of biochemical methods.

in vitro. Latin: meaning, outside the living cell. In a test tube or other artificial medium. Denotes the growth of explants in glass or other artificial environment.

in vitro selection. Selection for phenotypes (traits) expressed at the cellular or callus level which usually possess genetic changes that control the trait.

in vivo. Latin: meaning, in real life; in the living cell.

inbred. An individual resulting from the mating of closely related parents or selfing.

inbred line. A nearly homozygous breeding line produced by continued self-fertilization.

inbreeding. The interbreeding of closely related individuals occurring naturally (as in a closed population), or as a deliberately chosen system of breeding and serving especially to preserve and fix desirable characters of and to eliminate unfavorable characters from a suitably selected stock but tending to effect an unwanted decline (as in size, vigor, or fertility) through the fixation of undesirable and often recessive characters when the initial stock is any way defective.

inbreeding depression. Continuous breeding of genetically related individuals resulting in decrease in reproductive capacity.

incompatible. A plant that is unable to set seed or units when selfed, crossed, or grafted because of structural, physiological, or ontogenic reasons.

incomplete dominance. Two different alleles (e.g., dominant and recessive gene) producing an intermediate effect compared with effect of the dominant alleles.

incomplete fertilizer. A classification of fertilizers that contains only 1 or 2 of the major fertilizer elements N, P, and K.

incomplete tillage. The result of omitting one or more of the elements of a complete tillage system.

incorporate. To mix foreign materials, such as pesticides, fertilizers, or plant residues into the soil.

incubate. To provide (for seeds, embryos of animals, or bacteria) prescribed and usually controlled conditions (as temperature and moisture) favorable for development or hatching.

incubation period. Time after inoculation required for the symptoms of a disease to appear.

indehiscent. 1. Does not split open when ripe. 2. Does not open at maturity to discharge seeds.

independent assortment. Random assortment in which segregation for one type has no effect on any other alleles. Meiotic behavior of genes located on nonhomologous chromosomes.

independent variable. Variable that is not affected or influenced by other variables or factors.

indeterminate. When no flower bud growth ends the axis of the flower cluster on the inflorescence.

indica rice. One of the two major ecogeographical races of Oryza sativa (see also japonica). The major type of rice grown in the tropics and subtropics. It has broad to narrow, light green leaves and tall to intermediate plant stature (except for the semidwarf). Indica plants tiller profusely. Grains are long to short, slender, somewhat flat, and awnless. Indica grains shatter easily and have 23-31% amylose content. They grow mostly in the Philippines, India, Pakistan, Java, Sri Lanka, Indonesia, central and southern China, African countries, and other tropical regions.

indicator plants. Plants showing particular characteristics in response to specific soil or site conditions.

indigenous. Native to a particular area.

induced resistance. A type of pseudoresistance in which a plant temporarily acquires increased resistance from some conditions of plant or environment, such as change in soil fertility.

infest. To attack externally, e.g. by insect pests; attack on a part of a plant such as grain of rice. Also to contain the parasite.

inedible. Unpleasant, bad tasting, not possible to eat.

ineffective tillers. Tillers that do not bear panicles.

inert ingredient. Any ingredient in a formulation which has no pesticidal activity.

infect. To introduce or contaminate the plant with a pathogen or disease-producing substance. To invade and establish a parasitic relationship with the host plant.

infection. A stage in a disease cycle when the pathogen penetrates and establishes a parasitic relationship with the host.

infective insect. An insect that actually transmits a viral disease.

infestation. The presence of insects on a plant or on grain.

infiltration. The downward entry of water into the soil.

inflationary. Of, relating to, tending to cause inflation. Substantial and continuing rise in the general price level of commodities.

inflorescence. The flowering part of a plant including the bracts, flower stalks, and flowers.

influence. To modify the growth and development of a plant in any way by natural selection or research.

inherit. To receive a specific set of genes from the parents with particular traits; to transfer characteristics from parent to offspring.

inheritance. The process of genetic transmission of characters or characteristics.

inhibitory gene. A gene that inhibits the expression of other genes either in dominant or recessive form.

initial evaluation period. The first trial conducted in a program of testing to identify varieties or lines that could be retained for future trials.

inland valley swamps. Small to moderate sized valley bottoms in rainforest not associated with streams, which flood perennially or intermittently with stagnant water.

inoculate. To introduce microorganisms into another organism or medium.

inoculation. The introduction of an explant (any plant part) into a suitable medium for callus formation and ultimately plant production.

inoculum. Material (as spores, bacteria, or contaminated fluids) used in or suitable for use in inoculating or inoculation, e.g., portion of a pathogen (spores, mycelium, hypha in the case of fungi) or insect (eggs, young larvae) capable of being disseminated and causing infection/infestation.

inorganic. Of mineral origin.

inorganic fertilizer. Fertilizer materials derived from minerals, atmospheric gases, water, and inert materials. Can be natural or synthetic products of chemical reactions.

input. Money or other cost of production. Products added to the soil to improve plant production. Data into a computer. Personal contribution.

insect. Members of the phylum Arthropoda ("jointed legs"); they have six legs, three distinct body regions (head, thorax, and abdomen), one pair of antennae, and usually wings.

insecticide. A chemical used for killing insects.

instar. The stage of an insect between successive molts, the first instar being the stage between hatching and the first molt.

integrated pest management (IPM). A strategy that utilizes various tactics or control methods (cultural, biological, and chemical) in a harmonious way in which control actions are based on frequent monitoring of the pest. IPM depends on multidisciplinary ecological strategies to weigh the effect of each tactic, as part of the agroecosystem, in producing the least disturbance and yield loss in the long run.

integument. Something that covers or encloses, e.g., skin, husk, rind, outer layer of an insect.

interaction. The differential response of two or more factors which is more than can be attributed to chance.

interallelic. Between two different alleles of a gene, e.g. interallellic action is one which is influenced by two different alleles.

interbreeding. The use of plants capable of gene exchange by hybridization.

intercropping. Growing two or more crops simultaneously in alternating rows or sets of rows in the same plot (See also Mixed intercropping)

interflow. Shallow and often ephemeral and perched groundwater moving laterally.

internode. The portion of a stem between two nodes.

interfluve. An area of higher ground between two rivers flowing into the same drainage system.

intermediate. 1). The characters or traits of the plant between two different levels. 2). A substance which is in a metabolic pathway between two other substances.

intermittent irrigation. A method of applying irrigation water by which the field is alternately watered and drained. The soil surface is allowed to dry prior to the next application of water.

internode. The portion of the stem between two nodes. Smooth and solid (when young) or hollow; (when mature) part of the culm.

interspecific cross. A cross between two different species of a genus.

introduction. Cultivar of rice taken from one place to another.

introgression. Incorporation of genes of one species into the gene pool of another species by hybridization and backcrossing.

intron. Intervening sequence in genes. Transcribed but not translated.

inundate. To be completely submerged, e.g.. by floodwater.

inundation. The time of onset or arrival of the floods.

invasion. When an infectious agent attacks the host plant causing a disease.

inversion. A rearrangement of a chromosome segment so that its genes are in reversed linear order. Reverse order, e.g. warm air near the ground, cool air above.

involucre. A ring of bracts subtending a flower head.

iron toxicity. Disorder that occurs when the iron concentration in the soil solution is high. The symptoms of iron toxicity are many tiny brown spots on the green leaves which start from the tips and develop into a general browning of the leaf blades followed by the death of lower leaves.

irradiance. Radiant flux density on a given surface usually expressed in watts per square centimeter or square meter.

irradiation (genetics and plant breeding). Exposure of plants or plant parts to radiation to increase mutation rates.

irrigated rice. Rice which is supplementary or fully supported with water supplied by artificial means.

irrigated riceland. Rice areas that have assured irrigation for one or more crops per year. Some areas are served only by supplemental irrigation in the wet season.

irrigation. The artificial supply of water to areas by ditches, pipes, etc. by pumping or gravitation to the soil for the purpose of growing crops.

irrigation efficiency. The ratio of the water actually consumed by crops on an irrigated area to the amount of water diverted from the source onto the area.

irrigation methods. The manner in which water is controlled and applied to an area.

isogenic. Having the same genic constitution.

isogenic lines. Lines (families) which differ by one gene only.

isolate. 1). A single spore or culture and the subculture derived from it. Also used to indicate collections of a pathogen made at different times and/or space. 2). To remove or separate an individual sample from a given sample population.

isolation (barrier). 1). The growing into pure culture in artificial/synthetic medium of pathogenic microorganisms. 2). The separation of one group of plants from another so that fertilization between or among groups is prevented. Separation between two hybrid seed production plots can be provided by topographic surface features or artificial/natural barriers, to the height of at least 2.5 m., in the case of rice.

isolation (time) The separation can also be provided by growing two groups at different times of the crop season so that one group is already mature (stopped providing pollen) when the other group comes to flowering. Generally a 21-day difference in flowering is sufficient in the case of rice.

isoplasmic. CMS or restorer lines differing in nuclear genetic constitution but having a common cytoplasm.

isozyme. Also called allozyme. An enzyme which exists in multiple electrophoretic forms either because of allelic variation within one polypeptide or multimeric associations of variant forms. Similar or identical catalytic activities occur within the same organism.

ITCZ . intertropical convergence zone, or ITD, intertropical discontinuity; a broad trough of low pressure at the confluence of the trade winds which moves north and south roughly parallel to the equator with the seasonal change in the winds.

itinerary of techniques. The logical and well-ordered combination of techniques applied to a crop by the farmer to achieve a given production objective in a given environment.