Pathogenicity

the ability to cause disease.

Penetration

initial invasion of a host by a pathogen.

Penetration Peg

a structure found in some plant parasitic fungi. The penetration peg is a specialised, narrow, hyphal strand located on the underside of an appressorium that penetrates the epidermal cell wall.

Phenotype

the visible physical characteristics of an organism determined by the interaction of its genotype with the environment.

Phloem

the food-conducting and food-storing tissue in the roots, stems, and leaves of vascular plants.

Photosynthesis

the production of carbohydrates from carbon dioxide and water in the presence of chlorophyll(s), using light energy and releasing oxygen as a by product.

Phytoalexin

a substance produced in higher plants in response to a number of stimuli (chemical, physical or biological) that inhibits the development of a microorganism.

Phytoanticipin

these are constitutive phytoalexins i.e. phytoanticipins are synthesised by the plant at a constant rate and therefore always present in the tissues of the plant, whereas phytoalexins are only produced in response to a stimulus such as a pathogenic invasion. The distinction between phytoalexins and phytoanticipins is not always clear as some compounds may be phytoalexins in one species and phytoanticipins in another species. In general, the distinction between the two compounds depends on when they are produced (either before or after infection) and the extent to which the compound is antimicrobial (phytoalexins are antimicrobial).

Phytoplasmas

phloem -dwelling prokaryotic microorganisms, transmitted by phloem-feeding insects.

Powdery Mildew

White powdery 'bloom' on the plant surface caused by the production of fungal mycelium, conidiophores and conidia by members of the Erysiphales (powdery mildew fungi).
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Primary Inoculum

inoculum that initiates disease in the field following a dormant stage in its life cycle (called overwintering or oversummering). Compare with secondary inoculum.

Propagules

any part of an organism capable of independent growth (e.g., a spore, a mycelial fragment, etc.).

Protectant

any chemical agent that interacts with a pathogen on the plant surface to prevent infection.
- Protectant fungicide: a protectant that kills or inhibits the growth of fungi. See fungicide.

Pustule

A blister-like spore mass breaking through a plant epidermis.

Pleiotropic

having multiple effects.

Proteinaceous

of or related to protein.

Q

Quarantine

legal restriction of the transport of plants and/or plant parts in order to prevent the spread of pests and pathogens. In order to accomplish this plants may be held in isolation (i.e. quarantine) for an extended period of time to ensure that they are free of pests and diseases.

R

Race

a subgroup of pathogens within a species that infect a given set of plant varieties. Races may be distinguished from each other by virulence or symptom expression but not by morphology.

Resistant

possessing qualities that prevent or impede the development of a disease.

Resistance

the power of an organism to exclude or overcome, completely or partially, the effects of a pathogen or some other damaging factor.

Respiration

an intracellular process which consists of a series of chemical reactions that make energy available through the oxidation of carbohydrates, fats and proteins. This process produces carbon dioxide and water as byproducts and is termed aerobic respiration because it uses oxygen (although the initial stages of the process are anaerobic, i.e. do not require oxygen).

Дата добавления: 2015-10-31