You may find the following list of terms and definitions helpful if used to complement the glossary in your text on pages 607-618. Note that most plurals are formed by the addition of an "s" however, other plurals are shown in the list in parentheses after the term. Cross-references to similar or related terms in the list are shown by italics at the end of the definition.

Micheli - Observed in 1729 that spores of Rhizopus were associated with soft rot of melons - the spores were not considered to "cause" the disease.

Dr C. Montagne - French physician in Napoleon's army who identified and described the late blight fungus Phytophthora infestans.

Rev. M.J. Berkeley - First person to postulate that the late blight epidemic of 1845/1846 was caused by a fungus and the conducive weather conditions. Bitterly attacked by the "established" botanists of the day, who believed in the paradigm that fungi such as P. infestans were the product rather than the cause of plant disease and decay.

Anton de Bary - The Father of Plant Pathology. He was the first to determine and prove conclusively that P. infestans caused the Irish potato famine in 1861.

Alexis Millardet - The name of the man who, in 1885, developed/discovered the first fungicide - Bordeaux Mixture. (see Bordeaux Mixture)

Abiotic disease- disease or disorders caused by a non-living or non replicable entity, such as water or nutrient stress, wind, frost or hail. (see Biotic)

Acervulus (pl. Acervuli) - a cushion-like structure bearing asexual conidia of fungi in the Deuteromycete Order Melanconiales. Larger and more organized than a sporodochium, formed most commonly embedded in host tissue. (see Deuteromycete, Sporodochium, Conidium)

Acropetal - spore produced at the top of a chain of spores. (See Basipetal).

Aeciospore - dikaryotic spore produced by rust fungi that infects the alternate host species in heteroecious rust species; produced in a structure called an aecium (pl. aecia). (see heteroecious, basidiospore, teliospore, uredospore, spermatia).

Aflatoxin - a highly toxic mycotoxin produced by Aspergillus fumigatus on peanuts and other crops. (See Mycotoxin)

Alternate host - a second host REQUIRED for the completion of the life cycle of a plant pathogen (eg. Rust fungi). (see Alternative host)

Alternative host - a secondary host (often one of many) that may be colonized by a plant pathogen to complete part of the disease cycle (eg. weeds as overwintering hosts for viruses). Not required for completion of the life cycle! (see Alternate host)

Anamorph - asexual stage of Ascomycete fungi associated with production of conidia; classified in the Deuteromycetes. (see Ascomycete, Deuteromycete, Conidium, Teleomorph, Holomorph)

Antheridium - male gametangium of many fungi. (see Gametangium)

Apothecium (pl. Apothecia) - often large, fleshy, stalked disc or cup shaped fruiting body of the ascomycetes bearing asci and ascospores which are actively discharged and dispersed aerially. (see Ascus, Ascospores, Cleistothecium, Perithecium, Pseudothecium, Ascomycete)

Aseptate - Hyphae with no cross walls; coenocytic; typical of lower fungi (see Coenocytic, Septum)

Ascomycete - fungi that produces septate haploid mycelium, and sexual spores in an eight-spored sac-like ascus (ascospores) and asexual conidia. (see Ascospore, Conidia)

Ascospore - sexual spores of the ascomycetes produced after one meiotic and one mitotic cell division of a diploid zygote nucleus. Usually produced in groups of 8 inside an ascus. (see Ascus, Ascomycete)

Ascus (pl. asci) - sac-like structure containing (usually) eight ascospores. Characteristic of the ascomycetes. (see Ascomycete, Ascospore)

Autoecious - rust fungi that complete their life cycle on one host. (see Heteroecious, Microcyclic)

Basidiomycete - fungi with septa, often dikaryotic, mycelium that produce sexual haploid basidiospores. (see Basidiospore, basidium)

Basidiospore - sexual haploid spores of basidiomycetes produced on a club-shaped basidium after one meiotic division of a diploid zygote nucleus. (see Basidiomycete, Basidium)

Basidium (pl. basidia) - club-shaped cell that contains the diploid zygote nucleus of the basidiomycetes and which gives rise to four haploid basidiospores after a single meiotic division. (see Basidiomycete, Basidiospore)

Basipetal - spore produced at the bottom of a chain of spores (see Acropetal)

Biotroph - A parasite that requires living host tissue as a source of nutrients. (see Obligate parasite, Necrotroph)

Blight - Complete necrosis of above-ground plant parts (see Symptom, Necrosis).

Bordeaux Mixture - The name of the first fungicide discovered, by chance, to control downy mildew of grapes in 1885. (see Alexis Millardet)

Chlamydospore - Asexual, thick-walled, single-celled, overseasoning spore. (see Sclerotium)

Chlorosis - yellowing of host tissue. (see Symptom)

Chytridiomycete - simple fungi consisting of little more than a sporangium and sexual spores and restricted aseptate mycelium. Produce motile zoospores, cause several root rot diseases and act as virus vectors. (see aseptate, mycelium)

Clamp Connections - "clamp-like" fingers joining adjacent cells in Basidomycete hyphae to maintain the dikaryotic nature of the cells in the mycelium (see Basidomycete, Hypha, Dikaryon)

Cleistothecium (pl. Cleistothecia) - closed, sexual fruiting body of the Ascomycetes containing asci and ascospores adapted as overwintering structure. (eg Powdery mildews). (see Ascus, Ascospores, Apothecium, Perithecium, Pseudothecium, Ascomycete)

Coenocytic - Hyphae with no cross walls; aseptate; typical of lower fungi (see Aseptate, Septum)

Deuteromycete - fungi with septate mycelium bearing only asexual spores produced by mitosis (conidia), often asexual stages of Ascomycetes. (see Conidium, Ascomycete)

Dikaryon - Somatic cells of a fungus that contain two nuclei. (see Soma)

Disease Cycle - sequential stages of disease due to the different life stages of the pathogen and responses of the host to disease. (see Life Cycle)

Epinasty - downward bending of leaves and petioles without loss of turgor. (see Symptom)

Facultative Parasite - Organism able to survive indefinitely as saprophyte but capable of causing plant disease (e.g. Fusarium) (see Facultative saprophytes).

Facultative Saprophyte - Organisms which cause plant disease but with the ability to survive indefinitely as saprophytes (eg. Venturia inaequalis). (see Facultative parasite)

Haustorium (pl. Haustoria) - specialized feeding organ formed by many biotrophic fungi that invaginates the host plasma membrane and forms an intimate interface between the host and pathogen through which nutrients pass. (see biotroph)

Heteroecious - rust fungi that require two alternate hosts to complete their life cycle. (see Alternate host, Autoecious, Macrocyclic)

Heterothallic - two mating types required for sexual reproduction. Self-sterile or self incompatible individuals. (see Homothallic)

Holomorph - The totality of all stages of the life cycle of an Ascomycete fungus including all sexual and asexual spore stages; classified in the Ascomycetes and takes the same name as the teleomorph. (See Ascomycete, Deuteromycete, Anamorph, Teleomorph)

Homothallic - self-fertile individuals; sexual reproduction occurs on the same thallus. (see Heterothallic, Thallus)

Hyperplasia - abnormal increase in cell division. (see Hypertrophy)

Hypertrophy - abnormal cell enlargement. (see Hyperplasia)

Hypha (pl. hyphae)- filamentous, vegetative body of a fungus. (see Soma, Mycelium)

Indirect germination - germination of a sporangium by zoospores. (see Sporangium, Zoospore)

Karyogamy - fusion of two nuclei. (see Plasmogamy)

Latent Infection - Asymptomatic infection of a host until symptom expression is triggered by a specific physiological event such as ripening (Colletotrichum musae on banana).

Life cycle - the morphological stage or stages of an organism, each serving one or many ecological functions, which appear sequentially as the organisms grows, develops and reproduces. (see Disease Cycle)

Macroconidium (pl. Macrocondia) - large multicelled conidia produced by Deuteromycete fungi that produce more than one type of conidia. (see Microconidium, Deuteromycete)

Macrocyclic - rust fungus disease cycle which includes two alternate hosts. (see Alternate host, Heteroecious)

Meiosis - The "reduction " division, whereby a diploid or polyploid cell undergoes a sequence of two divisions that results in the daughter cell having (usually) half the number of chromosomes of the mother cell. Often associated with sexual reproduction (see Mitosis)

Microconidium (pl. Microconidia) - small, usually single-celled, conidia produced by Deuteromycete fungi that produce more than one type of conidia. (see Macroconidium, Deuteromycete)

Microcyclic - rust fungus disease cycle which includes only one host. (see Alternate host, Autoecious)

Mitosis - A vegetative cell division that results in daughter cells that are clones (ie. identical ) to the mother cell. Both mother and daughter cells have the same number of chromosomes. (See Meiosis)

Monocyclic - Disease epidemic caused by pathogens that complete only one disease cycle in one year (e.g. smuts, soilborne pathogens, vascular wilt pathogens). (see Polycyclic)

Mycelium (pl. Mycelia) - filamentous, vegetative body of a fungus consisting of many hyphae. (see Soma, Hypha)

Necrosis - death of host cells due to biotic or abiotic factors pathogen resulting in collapse and discoloration of tissue. (see Symptom)

Necrotroph - A parasite that lives on dead host tissue after killing the tissue with enzymes and toxins (see Biotroph).

Obligate parasite - A parasite that requires living host tissue as a source of nutrients. (see Biotroph)

Oogamy - Oogamous fertilization in which a large female gametangium (oogonium or egg cell) is fertilized by a small male gametangium (antheridium). (see oogonium, antheridium)

Oogonium - female gametangium of the oomycetes. (see Oomycete, Gametangium)

Oomycete - alga-like fungi that have diploid, aseptate hyphae, reproduce sexually by oospores and have asexual sporangia often containing motile zoospores. (see Oospore, aseptate, hypha, sporangia, zoospore)

Oospore - sexual, overwintering, spore of Oomycete fungi. Product of oogamous fertilization. (see Oomycete, Oogamy)

Ostiole - opening or pore in wall of closed fruiting bodies of Ascomycetes (Perithecium) and Deuteromycetes (Pycnidium) which allows active or passive dispersal of conidia from the fruiting body under suitable conditions. Breakdown of the fruiting body is not required for dispersal of spores. (see Perithecium, Pycnidium)

Parasite - An organism living in or on another living organism and obtaining nutrients from it, without necessarily giving benefit to, or causing damage to the host (see Pathogen, Symbiont, Saprophyte).

Pathogen - an organism or other replicable entity that damages a host plant thereby causing disease. (see Disease)

Pathogenicity - qualitative ability of a plant pathogen to cause disease. (see Virulence)

Perithecium (pl. Perithecia) - closed, ostiolate fruiting body of the Ascomycetes bearing asci and ascospores. Ascospores are active and passively dispersed by water and wind. (see Ostiole, Asci, Ascospores, Apothecium, Cleistothecium, Pseudothecium, Ascomycete)

Plasmogamy - fusion of two cells. (see Karyogamy)

Polycyclic - Disease epidemic caused by pathogens that complete many disease cycles in one year, often as a result of secondary inoculum (e.g. rusts, powdery mildews, downy mildews, Rhizopus). (see Monocyclic)

Primary inoculum - Type of inoculum that survives adverse conditions, overwinter or oversummer, and causes the first infections in the next growing season. (see Secondary Inoculum)

Propagule - a spore or other germinable structure, such as a sclerotium that can serve to propagate a pathogen (See Sclerotium).

Pseudothecium (pl. Pseudothecia) - closed ostiolate, stromatic fruiting body of the Ascomycetes bearing asci and ascospores. Ascospores are dispersed actively and passively by wind and water. (see Stroma, Ostiole, Asci, Ascospores, Apothecium, Cleistothecium, Perithecium, Ascomycete)

Pycnidium (pl. Pycnidia) - asexual, closed, ostiolate fruiting body of the Deuteromycetes, specialized for overseasoning and dispersal of conidia by water and wind. (see Deuteromycetes, Ostiole)

Saprophyte - an organism that obtains its nutrients from dead organic matter. (see Parasite)

Secondary inoculum - typically asexual spores of a pathogen acting as inoculum responsible for in-season and in-field spread of a disease after it has been established by the primary inoculum. (see Polycyclic, Primary inoculum) Inoculum responsible for polycyclic disease epidemics.

Septum (pl. septa) - Specialized cross walls in hyphae of higher fungi, separating hyphae into cells. (see aseptate, coenocytic)

Sclerotium - Asexual, thickwalled, multicelled, overseasoning structure. (see Chlamydospore)

Sign - The name given to the appearance of fruiting bodies and soma of the pathogen itself on the surface of a diseased plant (see Soma, Symptoms).

Soil Inhabitant - an organism that grows and reproduces in the soil environment (see Soil invader)

Soil Invader - an organism that exists in the soil only as a resting overseasoning propagule and does not grow or reproduce in the soil (See Soil Inhabitant, Propagule)

Soma (pl. Soma) - vegetative body of fungi; mycelium; hyphae. (see Mycelium, Hyphae)

Spermatia (sing. spermatium) - haploid spore produced in a spermogonium (pl. spermogonia) which fertilizes the receptive hyphae in a compatible spermogonium and leads to the production of dikaryotic hyphae. (see teliospore, uredospore, aeciospore)

Sporangiospore - asexual spores produced inside a specialized cell (sporangium). (see Sporangium)

Sporangium (pl. Sporangia) - Sack-like structure containing asexual spores (Sporangiospores) of lower fungi. (see Sporangiospore)

Sporodochium (pl. Sporodochia) - asexual, cushion-like fruiting body of Deuteromycete subclass Hyphomycetidae, adapted for water or splash dispersal of spores. Smaller and less organized than acervuli. (see Deuteromycete, Acervulus)

Sterigma (pl. Sterigmata) - short projection or hyphal branch which supports, and subtends, a sporangium, conidium or basidiospore. (see Sporangium, Conidium, Basidiospore)

Stroma - dense, tissue-like, fungal material often associated with fruiting bodies such as pseudothecia. (see Pseudothecium)

Symbiont - an organism living on or in another organism from which both organisms derive mutual benefit. (see Parasite)

Symptom - outward expression of disease by tissues of the host. (see Sign, Wilt, Chlorosis, Necrosis, Blight, Epinasty)

Synemma (pl. Synemmata) - asexual fruiting body, bearing conidia, that consists of an aggregation of hyphae forming a long stalk which raises the sporogenous head well above the substrata for dispersal of conidia by wind, water and insects. (see Conidium, Sporodochium, Acervulus, Pycnidium, Deuteromycete)

Teleomorph - stage of an Ascomycete fungus that represents the sexual stage; Classified in the Ascomycetes. (see Holomorph, Anamorph, Ascomycete)

Teliospore - the specialized probasidium (immature basidium) of rust fungi adapted specifically for overseasoning and which germinates by producing a club-shaped metabasidium (mature basidium) bearing four haploid basidiospores. (see basidium, basidiospores)

Thallus - vegetative body of a fungus; mycelium; hyphae; soma. (see Mycelium, Hypha, Soma)

Urediniospore - see Uredospore

Uredospore - the dikaryotic, asexual "summer" spore of rust fungi. Acts as secondary inoculum of the rust fungi and is often a rusty-orange color. Produced in the structure called a uredium (pl. uredia). Capable of reinfecting the host on which it is produced. (see Secondary inoculum, teliospore, aeciospore, spermatia)

Virulence - The degree of pathogenicity of a given pathogen. Often a quantitative term when comparing isolates in a given population. Quantitative term. (see Pathogenicity)

Witches' Broom - excessive proliferation of weak shoots or roots, rather like a straw-broom, arising from a bud or other meristematic region caused by fungi, mites, viruses or Mycoplasmas. (see Symptom)

Wilt - loss of turgor resulting in flaccidity of host tissue. (see Symptom)

Zoospore - asexual, motile spore of lower fungi. (see Oomycete, Chytridiomycete, Myxomycete, Plasmodiophoromycete)

Zygomycete - fungi with aseptate mycelium which produce sexual zygospores and asexual sporangiospores in sporangia. (see zygospore, sporangium, sporangiospore)

Zygospore - Sexual, overwintering, spore of zygomycetes resulting from fusion of two gametangia. (see Zygomycete)

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