Each entry consists of a term (in bold), a definition of the term, and a number in parentheses (0) indicating the source of the definition. Clicking on the speaker icon will give you the pronunciation of the term. (Be sure to close the window for the sound player after each use.) The pencil icon will give you a drawing, and the camera icon will give you a photograph.

saccate. Pouch- or sac-like. (14)

saltation. A mutation occurring in the asexual state of fungal growth, especially one occurring in culture. (20)

sanitation. Principle of plant disease control involving removal and burning of infected plant parts and decontamination of tools, equipment, hands, etc. (2)

saprobe. An organism that obtains its nutrients from non-living organic matter (commonly dead and decaying plant or animal matter) by absorbing soluble organic compounds. (Also saprotroph.) (16)

saprogenesis. Survival; that phase of the life cycle of a pathogen during which it is not actively causing disease in a living suscept. (20)

saprophyte. See saprobe.

saprotroph. See saprobe.

sarcody. A hyperplastic symptom in which swellings occur above and below portions of organs that are tightly encircled. (20)

satellite virus. A defective virus requiring a helper virus to provide functions necessary for replication. It may code for its own coat protein or various other products. (10)

scab. Any of a wide range of unrelated plant diseases having a roughened, crustlike diseased area on the surface of a plant organ (e.g., apple scab, potato scab, wheat scab). (2)

scabrous. Rough with short, rigid projections. (17)

scald. A necrotic condition in which tissue is usually bleached and has the appearance of having been exposed to high temperatures. (5)

sclerotium. Hard, resistant, multicellular resting body, usually with a differentiated cortex and medulla, that under favorable conditions can germinate to produce mycelium or sexual or asexual fruiting bodies. (Pl. sclerotia.) (22)

sclerotized. In nematodes: Hardened refractive regions. (14)

scolecospore. A very long, thin spore (with a length/width ratio more than 15:1). (12)

scolecosporous. Having long, thin (filiform) spores. (17)

scorch. "Burning" of leaf margins as a result of infection or unfavorable environmental conditions. (2)

scutellum. In nematodes: An enlarged, shield-like phasmid. (Pl. scutella.) (14)

secondary cycle. Of plant disease: any cycle initiated by inoculum generated during the same season. (21)

secondary infection. Any infection caused by inoculum produced as a result of a primary or a subsequent infection; an infection caused by secondary inoculum. (2)

secondary inoculum. Inoculum produced by infections that took place during the same growing season. (2)

secondary organism. An organism that multiplies in already diseased tissue but is not the primary pathogen. (5)

secondary rot. Rot caused by a secondary organism. (5)

secondary symptom. A symptom of virus infection appearing after the first (primary) symptoms. (5)

sedentary. Staying in one place; stationary. (2)

senescence. Decline or degeneration, as with maturation, age, or disease stress. (9)

senescent. Aged, degenerate. (17)

sensu lato. In a broad sense. (7)

sensu stricto. In a narrow sense. (7)

septate. Having cross walls. (2)

septum. A cross wall in a hypha or spore. (Pl. septa.) (15)

sequence. The order of nucleotides in RNA or DNA or of amino acids in a polypeptide. (10)

sequencing. Determining a sequence of a nucleic acid or protein. (10)

serology. Branch of science dealing with properties and reactions of sera, particularly the use of antibodies in the sera to examine the properties of antigens. (10)

serotype. A subdivision of virus strains distinguished by protein or a protein component that determines its antigenic specificity. (5)

seta. 1. In nematodes: Elongated cuticular structures articulating with the cuticle; in general, tactile sensory organs usually located around the oral openings. (14) 2. In fungi: A bristle-like structure in some types of fruiting bodies. (16) (Pl. setae.)

setose. Bristly; beset with bristles. (17)

sexual dimorphism. A pronounced difference in the morphologies of the two sexes within a species. (14)

serum. The fluid fraction of coagulated (clotted) blood. (16)

shock symptoms. The severe, often necrotic symptoms produced on the first new growth following infection with some viruses. Also called acute symptoms. (2)

shot hole. A symptom in which small, diseased fragments of leaves fall off, leaving small holes in their place. (2)

sieve plate. Perforated wall area between two phloem sieve cells through which they are connected. (2)

sieve tube. A series of phloem cells forming a long cellular tube through which food materials are transported. (2)

sigmoid. Doubly curved in opposite directions, like the Greek letter sigma. (17)

sign. A visible manifestation of a causal agent of plant disease (e.g., fungal spores or other fungal structures, bacterial ooze). (3)

slime mold. A member of a category of eukaryotic organisms that typically have some fungal-like attributes and some animal-like attributes. (16)

smut. Any of a number of plant diseases caused by the smut fungi (Ustilaginales); characterized by masses of dark, powdery, and sometimes odorous spores (e.g., stinking smut of wheat, common smut of maize). (16)

smut spore. A dark, thick-walled resting spore of a smut fungus; may germinate to produce a promycelium; often improperly termed a chlamydospore. (20)

somatic cell hybridization. Production of hybrid cells by fusion of two protoplasts with different genetic makeup. (2)

somaclonal variation. Variability in clones generated from a single mother plant, leaf, etc. by tissue culture. (2)

sooty mold. A fungus of the family Capnodiaceae and of certain other families of the order Dothideales. The organisms grow epiphytically, utilizing honeydew, and form dark, spongy, hyphal mats on the surfaces of certain plants. (16)

sorus. A cluster or mass of spores or sporangia. (Pl. sori.) (15)

Southern blotting. Procedure for transferring denatured DNA from an agarose gel to a nitrocellulose filter where it can be hybridized with a complementary nucleic acid. (13)

spear. See stylet. (14)

species. The basic category of biological classification, displaying a high degree of mutual similarity determined by a consensus of informed opinion; a subcategory of genus. (16)

species name. (Bot.) A Latin name consisting of two words, the generic name and the species epithet (e.g., Puccinia graminis). (22)

species epithet. (Bot.) The second word of a species name (e.g., graminis in the species Puccinia graminis). (22)

spermagonium. In certain fungi: a structure within which male reproductive cells (spermatia) are formed. In rust fungi, a spermagonium is called a pycnium. (Pl. spermagonia.) (16)

spermatheca. In nematodes: An enlarged portion of the female gonad between the oviduct and the uterus functioning in the storage of the sperm. (14)

spermatium. 1. A non-motile male reproductive cell that can function in spermatization. (16) 2. The male gamete of the rust fungi. See pycniospore. (2) (Pl. spermatia.)

spermatization. In certain higher fungi: the union of a spermatium with a female reproductive structure. (16)

spermatocyte. In nematodes: A cell giving rise to spermatozoa or spermatozooids. (18)

spicate. Having the form of a spike. (14)

spicule. Male copulatory organ. Sometimes called spiculum. (14)

spiroplasma. A member of a group of pleomorphic, wall-less prokaryotes occurring as epiphytes or as intracellular or extracellular parasites or pathogens in a range of invertebrates and plants. (2)

sporangiophore. A modified hypha that supports the sporangium. (15)

sporangiospore. An asexual spore produced within a sporangium. (15)

sporangium. A sac that bears endogenous, asexual spores (sporangiospores) (Pl. sporangia.) (15)

spore. A discrete sexual or asexual reproductive unit, usually enclosed by a rigid wall, capable of being disseminated. (15)

sporidiole. A little spore. (Also sporidiolum.) (17)

sporidiolum. See sporidiole.

sporidium. 1. A basidiospore formed by the rust or smut fungi. 2. In smut fungi: a spore formed in germination by repetition. (Pl. sporidia.) (16)

sporocarp. A fruit body that produces spores. (21)

sporodochium. A cluster of conidiophores arising from a stroma or mass of hyphae. (Pl. sporodochia.) (15)

sporophore. A spore-producing or spore-bearing structure such as a conidiophore, ascocarp, or basidiocarp. (15)

sporulate. To produce spores. (2)

sporulation. The process of producing spores. (20)

spot. A symptom of disease characterized by a limited necrotic area, as on leaves, flowers, and stems. (20)

spreader. A substance added to fungicide or bactericide preparations to improve contact between the spray and the sprayed surface; a surfactant. (11)

squamous. Covered with or consisting of scales. (14)

squamule. A small scale or lobe. (16)

staurospore. A non-septate or septate spore with more than one axis. (7)

staurosporous. Possessing staurospores. (17)

stem-pitting. A symptom of some viral diseases characterized by depressions on the stem of the plant. (2)

sterigma. A spike-like structure that supports a basidiospore on the basidium. (Pl. sterigmata.) (15)

sterile. 1. Unable to reproduce sexually. 2. To be free from living microorganisms. (20)

sterile fungus. A fungus that is not known to produce any kind of spores. (2)

sterilization. The elimination of pathogens and other living organisms from soil, containers, etc. by means of heat, chemicals, or radiation. (2)

sterilized. Free from living microorganisms. (20)

sticker. Added to fungicide or bactericide preparations to improve the adhesion of the spray to the sprayed surface. (11)

stipe. The stalk-like portion of some larger ascocarps or basidiocarps; any spore-bearing stalk. (15)

stoma. 1. In plants: Aperture in the epidermis of a leaf, stem, or fruit, bound by two guard cells and functioning in gas exchange. (4) 2. In nematodes: Buccal capsule. (14) (Pl. stomata.)

strain. A sub-species group of organisms distinguishable from the rest of the species by a heritable characteristic that the individuals in the group have in common. (3)

stomatostylet. See stylet. (16)

striae. In nematodes: Superficial grooves or clefts on the cuticle; when present, striae may be seen encircling lips or body. (14)

striate. Marked with delicate lines, grooves, or ridges. (7)

stroma. A compact mass of vegetative tissue, sometimes intermixed with host tissue, often bearing sporocarps either within or upon its surface. (Pl. stromata.) (15)

stylet. In nematodes: Hollow protrusible spear used to puncture plants or animal prey. (14)

stylet knob. One of the (usually three) basal protuberances of the stylet. (14)

stylospore. A spore borne on a filament or hypha. (17)

suberized. Of cell walls: Hardened by their conversion to cork (suberin). (20)

subsp.. Subspecies. (21)

subspecies. An infraspecific population defined on the basis of one or more characters (morphologic for most organisms) that distinguish its members from typical representatives of the species. (21)

substrate. 1. The material or substance on which a microorganism feeds and develops. 2. a substance acted upon by an enzyme. (2)

superinfection. Attempt to infect a host with a second virus, usually a different strain of the first infecting virus. (10)

supernatant. The material remaining above the pellet after centrifugation of a suspension. (10)

supplements. In nematodes: Preanal genital papillae on the ventral side of males; derived from cuticle, but may be provided with glands. Function during copulation. Sometimes called supplementary organs. (14)

suppression. A hypoplastic symptom characterized by the failure of plant organs or substances to develop. (20)

suppressive soil. A soil in which certain disease(s) fail to develop because of the presence in the soil of microorganisms antagonistic to the pathogen . (2)

suscept. Any plant that can be attacked by a given pathogen; a host. (2)

susceptible. Lacking the inherent ability to resist disease or attack by a given pathogen; not immune. (2)

susceptibility. The inability of a plant to resist the effect of a pathogen or other damaging factor. (2)

suspensor. A specialized hyphal tip that supports a gametangium and eventually a zygosporangium (in the Mucorales). (15)

swarmspore. Zoospore. (20)

symbiont. One member of a symbiotic relationship. (20)

symbiosis. A mutually beneficial association of two or more different kinds of organisms. (2)

symbiote. Symbiont. (20)

symptom. A visible abnormality in a plant that results from disease. (3)

symptomatology. The study of symptoms of disease and signs of pathogens for the purpose of diagnosis. (20)

symptomless carrier. A plant that, although infected with a pathogen (usually a virus), produces no obvious symptoms. (2)

synanamorph. Any one of the two or more anamorphs that are formed by the same fungus. (7)

syncytium. A multinucleate cell. (Pl. syncytia.) (14)

synergism. The concurrent parasitism of a host by two pathogens in which the symptoms or other effects produced are of greater magnitude than the sum of the effects of each pathogen acting alone. (2)

synnema. A fascicle of conidiophores, usually upright; a coremium. (Pl. synnemata.) (15)

syntype. One of a number of specimens of equal nomenclatural rank that formed all or part of the material the original author had in cases in which the author did not designate or indicate a holotype. (14)

systemic. Of a chemical or a pathogen: Spreading internally throughout the plant body. (2)

systemic infection. In virology, an infection resulting from the spread of virus from the site of infection to all or most cells of an organism. (10)