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.

caeoma. An aecium in the Uredinales that is not surrounded by a peridium; from the form genus Caeoma. (Pl. caeomata.) (17)

callus. A mass of thin-walled, undifferentiated plant cells, developed as the result of wounding or culture on nutrient media. (2)

canker. An imprecise term usually used for a plant disease characterized (in woody plants) by the death of cambium tissue and resulting loss and/or malformation of bark, or (in non-woody plants) by the formation of sharply delineated, dry, necrotic, localized lesions on the stem. The term "canker" may also be used to refer to the lesion itself, particularly in woody plants. (16)

capillitium. A mass of sterile fibers interspersed among spores within a sporocarp (in the Gasteromycetes and Myxomycota). (Pl. capillitia.) (15)

capitulum. In nematodes: Medial ventral sclerotization of the spicular pouch. (14)

capsid. The protein shell that surrounds the virus nucleic acid. (10)

capsule. In bacteria: A layer of material external to but contiguous with the cell wall. (16)

cardia. In nematodes: Valvular apparatus connecting the esophagus and intestine. Sometimes called the cardiac valve or esophago-intestinal valve. (14)

carlavirus. (Siglum of carnation latent virus.) Member of a group of plant viruses with slightly flexuous, rod-shaped particles containing a single molecule of linear RNA, most of which are transmitted by aphids in a noncirculative manner. (5)

carmovirus. (Siglum of carnation mottle virus.) Member of a group of plant viruses with small, isometric particles containing a single molecule of linear RNA, transmitted in nature through soil and (rarely) by an insect vector. (5)

carrier. An organism that bears an infectious agent internally but shows no marked symptoms of the disease caused by that agent. (20)

caudal. In nematodes: Pertaining to or located near the posterior region or tail. (14)

causal agent of disease. That which is capable of causing disease. (20)

cell cycle. The period from one cell division to the next. (13)

cephalic. In nematodes: Pertaining to or located near the head. (14)

cephalids. In nematodes: Two structures (posterior and anterior) situated in the cephalic region and extending in a complete circle around the body; possibly part of the nervous system. Sometimes called hypodermal commisures. (14)

cfu. Colony-forming unit. (16)

chemotherapy. The use of chemical(s) (e.g., antibiotics or fungicides) for the treatment of a disease. (16)

chlamydospore. A thick-walled, nonsexual spore; a transformed hyphal cell. (15)

chloranemia. The necrotic symptom of yellowing; a loss of chlorophyll. (20)

chlorosis. The loss of chlorophyll from the tissues of a plant, resulting from microbial infection, viral infection, the action of certain phytotoxins, the lack of light, to magnesium or iron deficiency, etc. Chlorotic tissues commonly appear yellowish. (16)

chlorotic. See chlorosis.

chord. In nematodes: A longitudinal internal thickening of the hypodermis. (14)

circulative transmission. Virus transmission characterized by a long period of acquisition of the virus by a vector, a latent period of several hours before the vector is able to transmit the virus, and retention of the virus by the vector for a long period, usually several days. (Also termed persistent transmission)

cirrhus. (Also cirrus.) 1. A mass of spores in the form of a ribbon or tendril, forced from the fruiting body of a fungus. (21) 2. A discrete group of somatic cilia (several to over 100) that act primarily as a unified locomotive organelle; the typical cirrus is conical. (16) (Pl. cirrhi or cirri.)

clamp connection. A recurving outgrowth of a cell that, at cell division, acts as a bridge to allow passage of one of the products of nuclear division into the penultimate cell, thereby assuring maintenance of the dikaryotic condition (of members of the Basidiomycotina). (15)

clavate. Club-shaped. (14)

cleistothecium. An ascocarp with the asci surrounded by fungal tissue and without regularly formed openings. (Pl. cleistothecia.) (15)

cloaca. In nematodes: A common duct or cavity in which the digestive and reproductive systems terminate in males. (14)

clone. 1. (n.) (a) A population of recombinant DNA molecules all carrying the same inserted sequence; (b) a colony of micro-organisms containing a specific DNA fragment inserted into a vector; (c) a population of cells or organisms of identical genotype. 2. (v.) (a) the use of in vitro recombination techniques to insert a particular DNA sequence into a vector; (b) the selection of a unique virus isolate from individual plaques, pocks or lesions or by limiting dilution; (c) the vegetative propagation of an organism to produce a population of identical individuals. (10)

cloning. An in vitro procedure in which a particular sequence of DNA (e.g., a gene) is reproduced in large amounts by inserting ("splicing") it into a suitable replicon, introducing the resultant recombinant (hybrid) molecule into a cell in which it can replicate, and finally growing the cells in culture. (16)

closterovirus. (from Greek kloster, "thread") Member of a group of plant viruses with very long, flexuous, rod-shaped particles containing a single molecule of linear RNA, some members of which are transmitted by whiteflies. (5)

cluster cup. Aecidium. (20)

coalesce. To merge or grow together into a similar but larger structure. (5)

coccus A spherical (or near-spherical) bacterial cell. (Pl. cocci). (16)

codon. A particular sequence of three nucleotides in mRNA coding for an amino acid. (16)

Coelomycetes. A group of the Deuteromycetes producing pycnidia or acervuli. (22)

coenocyte. A multinucleate cell; a protoplast in which the nuclear divisions have not been followed by cytoplasmic cleavage. (17)

coenocytic. Multinucleate or without cross walls. See syncytium. (17)

coenozygote. A cell containing more than one zygote. (22)

commensalism. Symbiosis in which neither organism is injured; one or neither may be benefited. (20)

commisure. In nematodes: Connecting bands of nerve tissue. (14)

comovirus. (Siglum of cowpea mosaic virus). Member of a group of multicomponent plant viruses with small, isometric particles containing two linear RNA species, readily transmitted mechanically and by beetles. (5)

compartmentalization. In trees: the processes that result in isolation of wounded or diseased xylem from normal xylem by the formation of chemically and anatomically specialized tissue around the damaged zone. (21)

competition. A more or less active demand on the part of two organisms for some commodity (space, food, etc.) that is inadequate to provide for all organisms present. (15)

conidiogenesis. Conidium formation. (16)

conidiogenous cell. A conidium-producing cell. . (16)

conidioma A specialized, multi-hyphal structure bearing conidia. (Pl. conidiomata.) (7)

conidiophore. A hypha, often specialized in structure, that bears one or more conidia. (15)

conidium. A thin-walled, asexual spore that is borne exogenously on a conidiophore and is deciduous at maturity. (See endoconidium.) (Pl. conidia.) (15)

conjugate. To carry out conjugation. (16)

conjugation. In general, any of various sexual processes in microorganisms in which gene transfer follows the establishment of direct contact between two (or more) cells which typically show little or no morphological differentiation from vegetative cells. In bacterial conjugation, one bacterium (the "male" or donor cell) transfers DNA to another (the "female" or recipient cell) while the cells are in physical contact; a recipient that has received DNA from a donor is called a transconjugant. (16)

conk. The basidiocarp of a wood-decaying fungus, usually a polypore. (21)

context. The inner or body tissue of a fruit body which supports the hymenophore in the larger and especially the pileate species of Hymenomycetes. (17)

control. Economic reduction of crop losses caused by plant diseases. (20)

coremium. See synnema. (Pl. coremia.) (16)

cornute. Horned; horn-like. (17)

corpus. In nematodes: The anterior cylindrical part of the esophagus. The basal region of the corpus at times may be swollen to form a bulb. (14)

coryneform. 1. Essentially rod-shaped with one end thickened or bulbous. 2. A name applied, loosely, to any Gram-positive, asporogenous, pleomorphic rod-shaped bacterium; as such it covers bacteria from a range of genera. (16)

cosmid. A plasmid into which has been inserted the cos site of bacteriophage. (16)

crop rotation. The practice of growing a sequence of different crops on the same land in successive years or seasons; done to replenish the soil, curb pests, etc. (1)

cross-protection. The protection conferred on a host by infection with one strain of a virus that prevents infection by a closely-related strain. (10)

crozier. A recurved hook at the tip of an ascogenous hypha, the penultimate cell of which will become the ascus. (15)

crozier formation. Process of ascus development from coiled tips of ascigerous hyphae. (20)

crustaformeria. In nematodes: Glandular region of the distal part of uterus that may play a role in the formation of the egg envelope; sometimes called the quadricolumella. (14)

cucumovirus. (Siglum of cucumber mosaic virus). Member of a group of multicomponent plant viruses with isometric (icosahedral) particles consisting of three linear RNA species (RNAs 1, 2, and 3), transmitted by sap and in nature by aphids in a noncirculative manner. (5)

cultivar. A cultivated plant variety or cultural selection. (5)

culture. 1. To grow an organism. 2. the resulting growth. Usually on artificial medium. (15)

culture collection. A repository of cultures of characterized viruses, bacteria, and other organisms. Used for reference and comparison with new isolates. (10)

cupulate. Cup-shaped. (5)

cuticle. 1. A thin, waxy layer on the outer wall of epidermal cells consisting primarily of wax and cutin. (2). 2. Noncellular exterior covering of nematodes. (14)

cutin. An insoluble polymer that, embedded in waxes, forms the cuticle covering the epidermal cell walls in the aerial parts of higher plants. (16)

cutinolytic. Of certain enzymes: able to digest cutin. (21)

cutis. Of basidiocarps of certain wood-decaying fungi: the outer layer consisting of compressed hyphae parallel to the surface, sometimes with varnishlike incrustation. (21)

cv. Cultivar. (5)

cylindrical. Of the stipe, spores, etc.: Of the same diameter throughout the length. (17)

cyst. In fungi: An encysted zoospore. In nematodes: the egg-containing carcass of dead adult females of the genus Heterodera or Globodera. (2)

cystidium A sterile cell occurring among basidia and often projecting beyond the hymenium, differing morphologically from the basidium. (Pl. cystidia.) (15)

cytokinins. Phytohormones that stimulate metabolism and cell division. (16)