wart. A small, blunt-tipped, rounded outgrowth.
water control. To control the amount and depth of water in the ricefield during the required time necessary for crop growth.
waterlogged field. A field which continuously has standing water and cannot be drained. The water level may not be deep.
waterlogging. Impeded drainage; or soil saturated with water but not necessarily with standing water.
watershed. The total area from which a single river collects surface water runoff; the catchment or drainage area of a river system.
watershed degradation. A marked deterioration in the hydrological behavior of a river system which reduces the potential of land and water by causing a water flow of inferior quality, quantity and timing.
water table. The upper surface of ground water and the level below it where the soil is saturated with water.
water use efficiency. 1). Expressed in terms of dry matter or harvested portion of the crop produced per unit of water consumed. 2). Ratio of the water used for evapotranspiration, seepage, and percolation to the sum of rainfall and irrigation supply.
waxy (glutinous) rice. Milled rice with negligible or no amylose in the grain.
waxy endosperm. Glutinous or waxy type of starchy endosperm, in which the starch fraction is composed of nearly 100 % amylopectin, 0-2% amylose, stains reddish brown with weak potassium iodide-iodine solution.
weed control. Prevention or eradication of weeds by physical removal (hand weeding) or limiting their growth by mechanical or chemical means.
weed. Any unwanted plant that is injurious to the crop.
weedicide. A term used for chemicals that control weeds.
weeding. Removing unwanted plants by hand from a crop, or tillage action which lightly cultivates the soil for the purpose of destroying the weeds.
weevil. The adult form of a certain coleopterous species.
well puddled. Said of muddy, very wet ricefield ready for sowing.
western hybridization. Also called western blotting. Method to detect protein by use of an antibody directed against it.
wetbed method. Raising seedlings on a seedbed where land is prepared and puddled.
wetbed seeding. Planting of pregerminated seed or small seedlings into a wet seedbed.
wetland. 1). Pertaining to soils flooded for at least several weeks each year, or to crops growing in such soils. 2). Land of which the rooting zone can be kept saturated for a substantial part of the growing season, where necessary, by encouraging accumulation of water on the soil through puddling and the use of bunds or levees.
wettable powder (WP). A pesticide formulation consisting of talc or clay and a wetting agent mixed with the pesticide. When water is mixed with the formulation, a suspension is formed and is used to spray on the target pest.
wetland tillage. Preparing the soil by plowing of lowland fields and harrowing the soil in a saturated or flooded condition.
wetting agent. A substance that renders a surface non-repellent to a wetting liquid.
wheel track planting. A practice of planting in which the seed is planted in tracks formed by wheels rolling immediately ahead of the planter.
white belly. A chalky white spot in the lateral part of the endosperm.
white center. The chalky area in the center of the endosperm of the milled nonglutinous rice.
white stem borer. It lays its eggs in batches of about 100 which are covered with silky grayish hairs. Incubation period is about 8 days. The larva is similar to yellow borer larva, except that it is white and reaches full growth in about 30 days. Pupation is completed in about 8 days. The adult lives for about 7 days. It is white and slender. It resembles the yellow rice borer, but does not have a black spot on the forewing. The abdominal tip of the female is pink. The life cycle of the white stem borer is completed in about 53 days. Scientific name: Scirpophaga innotata.
white tip. A disease of rice caused by the nematode Aphelencoides besseyi, with symptoms consisting of chlorosis of the leaf tips which become brownish and tattered. The infected plants are stunted and produce a few, small spikelets/panicles.
whitehead. White, empty panicles resulting from the attack of stem borers that cut the lower portion of the stem. Whitehead can also be caused by drought, dry wind, or desiccation.
whiteness. Measured with a Kett Whiteness Meter Model C-3 (Malaysia, IRRI).
whole kernel (white rice). The unbroken kernel of rice that has been milled.
whorl. 1). A ring of similar organs arising from a node. 2). The arrangement of leaves in a circle.
whorl maggot. Hydrellia philippina, the larva of which feeds on leaves in the whorl.
wide cross. Cross between two distantly related species.
wide hybridization. Hybridization between plants belonging to different species or genera. It is also referred to as interspecific, intergeneric, remote or distant hybridization.
wild rice. Species of Oryza that are not cultivated.
wilt. A characteristic of the plant indicated by drooping, folding, rolling, or collapsing leaves due to an unfavorable water balance.
wilting. The loss of turgidity in plant tissue where the intake of water is insufficient to replace that lost by transpiration or other means, causing a deflation of the plant cells.
wilting coefficient. The percentage of water necessary for a plant that has begun to wilt to recover, if that water is supplied.
wilting point. Reached when the soil cannot supply enough water to balance the plant's losses by transpiration.
windbreak. A planting of trees, shrubs, or other vegetation, usually perpendicular or nearly so, to the principal wind direction, to protect soil, crops, homesteads, roads, etc., against the effects of winds, such as wind erosion and the drifting of soil and snow.
woody. Hard in texture.
working collection. A sizable number of evaluated accessions that is stored, documented, and frequently used in breeding research.
world collection. A comprehensive collection of samples from different geographic areas of the world which is documented and stored. These are kept in storage as a genetic stock, and available to all for breeding purposes or reestablishment of a variety in a given location. Only segments of the world collection are of immediate practical value and thus find their way into the working collection.