Disease Severity

the measure of damage done by a disease.

Dominant

a gene is said to be dominant if it expresses its phenotype (physical characteristic) even when contributed by only one of the parents.

Downy Mildew

white or grey 'bloom' on leaves and stems caused by production of sporangiophores and sporangia by members of the Peronosporales (downy mildew fungi).

E

Ectodesmata

Ectodesmata are pits in the outer wall of epidermal cells, which connect to valleys in the cuticle surface, exposing the plasma membrane. Plant metabolites leak from the ectodesmata and accumulate in the valleys on the leaf surface, providing nutrients for pathogens and saprophytes.

Ectoparasite

a parasite that lives and feeds from the exterior of its host's cells or tissues. Compare with endoparasite.

Elicitor

a molecule produced by the host which induces a response by the pathogen. Conversely, an elicitor can be produced by a pathogen, eliciting a response in the host.

Endoparasite

a parasitic organism that lives and feeds within the cells or tissues of its host. Compare with ectoparasite.

Endobiotic

describes an organism living within the cells or tissues of a host organism. Endobiotic organisms are endoparasites.

Enzyme

a protein produced by living cells that can speed up (catalyse) specific biochemical reactions but which itself remains unaltered in the process.

Epiphytic

living on the surface of a plant, but not as a parasite and without causing infection.

Eradication

the control of plant disease by eliminating the pathogen after it is established or by eliminating all of the plants that carry the pathogen.

Exclusion

a method of disease prevention in which the pathogen or infected plant material is excluded from crop production areas. See quarantine.

Extracellular

outside a cell.

TF

Fungicide

a substance (chemical or physical) that kills or inhibits the growth of fungi.

G

Gall

an abnormal growth or swelling produced as a result of pathogenic invasion.
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Gene Expression

conversion of the information encoded in a gene via transcription and translation, resulting in the production of a protein and the appearance of the phenotype determined by that gene.

Genotype

the genetic makeup of an individual or group.

Gum

gelatinous, sugary substance that is synthesized and secreted by plant tissues.

H

Haustorium (pl. Haustoria)

a specialized branch of a fungal hypha formed inside a living cell of the host plant in order to obtain nutrients.
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Hemibiotroph

a parasite that initially forms an association with living cells of the host, much like a biotroph, and then in the later stages of infection it becomes necrotrophic, actively killing host cells.

Host

an organism harbouring a parasite or pathogen.

Host Range

the range of plants on which an organism feeds, particularly a parasite; the range of plants in which a pathogen is capable of causing disease.

Hydathode

a specialized epidermal leaf structure with one or more openings through which water is discharged from the leaf interior to its surface.
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