Glossary

A - B - C - D - E - F - G - H - I-K - L - M - N-O - P-Q - R - S - T - U - V - W-Z

A


Aeciospore - a spore produced in the aecidium
Aecidium - in rust fungi a cup-shaped structure containing chains of spores
Alternate host - a second host (of a different plant species) required by some pathogens in order to complete their life cycle
Anamorph - the imperfect or asexual stage of a fungus
Apothecium - a cup- or saucer-like ascocarp
Asexual - without sex organs or sex spores: vegetative
Ascocarp - a fruiting body which bears asci
Ascospores - sexually produced spores contained within an ascus
Ascus (pl. asci) - a sac-like cell which contains the products of the sexual stage (teleomorph) as

 

B


Basidiocarp - a fruiting body which bears basidia
Basidiospores - (sexually produced) spores borne on the outside of a basidium
Basidium - a cell or organ from which the sexually produced basidiospores (generally 4) are formed
Biotroph - an organism entirely dependent upon another living organism (the host) as a source of nutrients
Boot - characteristic swelling in the stem of a cereal plant, produced as the developing ear moves up the stem
Break crop - a crop (e.g. oilseed rape) grown in rotation with other crops (e.g. wheat) to improve the growing conditions of the following crop

 

C


Chlamydospore - an asexual spore arising from a hyphal segment, a resting stage
Chlorosis - the yellowing of normally green plant tissue
Cleistothecia - the closed spherical ascocarp of the powdery mildews
Coalesce - to unite or come together in one body or mass
Coleoptile - protective sheath surrounding the emerging shoot of a cereal
Conidia - asexual fungal spores formed from the end of a conidiophore
Conidiophore - a specialised hypha on which one or more conidia are produced
Cortex - the layer of cells between the epidermis and the vascular bundles
Cotyledon - part of the embryo that forms the primary leaf
Crown roots - the roots which emerge from the base of the stem of the plant rather than the seed

 

D


Damping-off - disease of plant seedlings caused by seed- or soil-borne fungi
Dicotyledon - a flowering plant whose embryo has two cotyledons (seed leaves)
Dieback - necrosis of a shoot beginning at the apex and spreading towards the older tissue, stem death may occur
Direct drilling - the drilling of seed into ground which has received minimal cultivation

 

E


Ear blight - infection of cereal ears resulting in bleaching of parts of the ear or discolouration of the glumes and grains
Ear primordial - original formation of the ear
Endosperm - nutritive tissue in a seed
Epidemic - a widespread increase in the incidence of an infectious disease
Epidermis - the outermost layer of cells of an organ, usually only one cell thick
Ergot - the fruiting structure (sclerotium) of Claviceps spp.

 

F


Flag leaf - the final leaf to emerge in a cereal plant
Focus (pl. foci) - a site of local concentration of diseased plants, usually about a primary source of infection or coinciding with an area originally favourable to disease establishment
Forma specialis (f. sp) - a group within a pathogen species that can only infect particular hosts

 

G


Glume - an outer and lowermost bract of a grass (including cereals) spikelet (inflorescence)

 

H


Honeydew (fungal) - a sticky secretion containing conidia produced during the lifecycle ofClaviceps purpurea (Ergot)
Host - a living organism harbouring a pathogen
Host specific - pertaining to a particular host, generally species specific
Hybrid - cross between two varieties or species of plant or animal
Hypha - one of the filaments of a mycelium

 

I - K

Immune - cannot be infected by a given pathogen
Inoculum - micro-organisms or virus particles which act as a source of infection
Inflorescence - the group or arrangement in which flowers are borne on a plant
Internode - part of a plant stem between two successive nodes

 

L


Leaf sheath - the lower part of the leaf which surrounds the stem more or less completely
Lesion - a localised area of diseased tissue
Lodging - when a standing crop is caused to lean or bend due to adverse weather or soil conditions

 

M

Minimal cultivation - a reduced form of cultivation
Morphology - the form and structure of an organism
Mosaic - a pattern of disease symptoms on a plant apparent as green/yellow or dark/light areas, usually referring to virus infections
Mycotoxin - a toxin produced by a fungus
Mycelium - the mass of hyphae forming the body of a fungus

 

N-O


Necrotroph - micro-organism feeding only on dead organic tissue
Node - the level of a stem at which one or more leaves arise
Ovary - the core of the carpel of a flower, in which seeds are produced

 

P-Q


Pathogen - an organism which causes disease
Perithecium - an ascocarp shaped like a flask containing asci
Primary inoculum - spores or fragments of mycelium capable of initiating disease
Pseudothecia - a peritheca-like structure with a single cavity containing ascospores
Pustule - a spore mass developing below the epidermis and then breaking through at maturity
Pycnidium - flask shaped fruiting body with an apical pore lined internally with pycnidiospores
Pycnidiospores - spores from within a pycnidium

 

R


Rachis - the main axis of the inflorescence, or spike, of wheat and other cereals, to which the spikelets are attached
Resistance - the inherent capacity of a host plant to prevent or reduce the development of a disease

 

S


Saprophyte - an organism deriving its nutrients from dead or decaying tissue of another organism
Sclerotia - compact mass of fungal hyphae e.g. ergot, capable of being dormant for long periods, and giving rise to fruiting bodies or mycellium
Seminal roots - the roots developing directly from the seed
Senescence - the dying process of a plant or plant part
Sporangiophore - a hypha or fruiting structure bearing spores
Sporangium - a container or case of asexual spores. In some cases it functions as a single spore
Spore - a reproductive unit in fungi
Sporulation - the period of active spore production
Susceptible - non-immune i.e. capable of becoming infected by a Pathogen

 

T


Telium - structure containing teliospores
Teliospores - sexual spores produced within a telium
Teleomorph - the sexual or so-called perfect growth stage or phase in fungi
Tolerance - the ability of a plant host to sustain the effects of a disease without dying or suffering serious injury or crop loss 
Toxic alkaloids - harmful substance found in plants which use them as defence against herbivores

 

U


Uredium - the fruiting structure of a rust fungi in which uredospores are produced
Uredospore - the asexual spore of the rust fungus

 

V


Vascular tissue - in plants, xylem and phloem.
Vector - an organism capable of transmitting inoculum
Virulence - the ability of a pathogen to produce disease

 

W-Z


White-head - prematurely ripened ears of cereals often caused by pathogens attacking the roots or stem base
Xylem - tissue within plants which conducts water and mineral salts, absorbed by roots from the soil, throughout the plant