Alternate host                         

A second host (of a different plant species) that is required by some pathogens 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 that bears asci

Ascospores

Sexually produced spores contained within an ascus

Ascus (pl. asci)                       

A sac-like cell that contains the products of the sexual stage (teleomorph) as ascospores (usually eight)

Basidiocarp

A fruiting body that 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 four) are formed

Biotroph

An organism entirely dependent upon another living organism (the host) as a source of nutrients

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

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 (chasmothecia) mildews

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

Cotyledon

Part of the embryo that forms the primary leaf

Crown roots

Roots that emerge from the base of the stem of the plant rather than the seed

Damping off

Disease of plant seedlings caused by seedborne or soilborne fungi

Dicotyledon

A flowering plant that has an embryo with two cotyledons (seed leaves)

Die-back

Necrosis of a shoot, beginning at the apex and spreading towards the older tissue; stem death may occur

Direct drilling

Drilling seed into ground with minimal cultivation

Ear blight

Infection of cereal ears resulting in bleaching of parts of the ear or discolouration of the glumes and grains

Endosperm

Nutritive tissue in a seed

Epidemic

The widespread incidence of an infectious disease in a population

Epidermis

The outermost layer of cells of an organ, usually only one cell thick

Ergot

The fruiting structure (sclerotium) of Claviceps spp.

Flag leaf

The final leaf to emerge in a cereal plant

Focus (pl. foci)

A concentrated area of diseased plants, usually around a primary source of infection, or coinciding with an area particularly favourable to disease

Forma specialis (f. sp.)

A group within a pathogen species that can only infect particular hosts

Glume

The outermost and lowermost bract of a grass (including cereals) spikelet (inflorescence)

Honeydew

A general term to describe a sticky secretion produced by some organisms, such as aphids or the pathogen Claviceps purpurea. Honeydew of the latter, which causes ergot, contains conidia.

Host

A living organism that harbours another (e.g. a pathogen)

Host-specific

Pertaining to a particular host; usually species-specific

Hypha

One of the filaments of a mycelium

Immune               

Cannot be infected by a given pathogen

Inoculum

Microorganisms or virus particles that 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

Leaf sheath

The lower part of the leaf that more or less completely surrounds the stem

Lesion

A localised area of diseased tissue

Lodging

When a standing crop leans or bends; for example, because of adverse weather or soil conditions

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

Necrotroph

A microorganism that feeds only on dead organic tissue

Node

The level of a stem from which one or more leaves arise

Pathogen

An organism that causes disease

Perithecium

A flask-shaped ascocarp, containing asci          

Primary inoculum

Spores or fragments of mycelium capable of initiating disease

Pseudothecia

Perithecium-like structures, each with a single cavity containing ascospores

Pustule

A spore mass that develops below the epidermis and breaks through at maturity

Pycnidium

Flask-shaped fruiting body, with an apical pore lined internally with pycnidiospores

Pycnidiospores

Spores from within a pycnidium

Rachis

The main axis of the inflorescence, or spike, of cereals to which the spikelets are attached

Resistance

The inherent capacity of a host plant to prevent or reduce the development of a disease

Saprophyte

An organism that derives its nutrients from dead or decaying tissue of another organism

Sclerotia

Compact masses of fungal hyphae (e.g. ergots), capable of remaining dormant for long periods and giving rise to fruiting bodies or mycelium

Seminal roots

Roots that develop 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

Species

Organisms in which the members have similar characteristics to each other and can breed with each other. Plural abbreviated as spp.          

Susceptible

A host plant unable to prevent or reduce the development of a disease

Telium

Structure containing teliospores

Teliospores

Sexual spores produced within a telium

Teleomorph

In fungi, the sexual, or so-called 'perfect', stage or phase of growth

Tolerance

The ability of a plant host to sustain the effects of a disease without dying or suffering serious injury or crop loss

Uredium

The fruiting structure of a rust fungus in which uredospores are produced

Uredospore

The asexual spore of the rust fungus

Vector

An organism capable of transmitting inoculum

Virulence

The ability of a pathogen to produce disease

White heads (bleached ears)

Prematurely ripened ears of cereals, often caused by pathogen damage of the roots or stem base