Glossary

Ability of an otherwise susceptible variety of plant to escape infection because of the way it grows (e.g., early-maturing plants escape late-season diseases).

Present but not manifest or visible, as a symptomless infection.

a natural opening in the surface of a fruit, root, stem, or tuber for gas exchange.

A local injury or delimited diseased area.

The death or disintegration of cells and tissues in a localized area of an organ.

Visible to the naked eye, without the aid of a microscope.

the retention of dead plant organs, such as leaves, which normally are shed. Several trees, including certain oaks, normally have marcescent leaves.

a plant tissue characterized by frequent cell division, producing cells that become differentiated into specialized tissues.

A millionth of a meter (or, a thousandth of a millimeter).

Visible only with the aid of magnification.

nematodes that feed from outside roots, moving from cell to cell and piercing them to feed without entering root tissue. (Examples: dagger nematodes, Xiphinema spp.)

nematodes that feed inside roots,
tunneling inside and moving back into soil and to new roots at will. (Examples: root-lesion nematodes, Pratylenchus spp.)

Having only one flagellum.

Disease symptom characterized by nonuniform foliage coloration, with a more or less distinct intermingling of normal and light green or yellowish patches. Usually caused by a virus.

An irregular pattern of light and dark areas.

The drying up and shriveling of fruits and other plant parts.

A dried and shriveled fruit partially or completely replaced with fungal structures

A conspicuous fleshy fungus fruiting body.

The mass of interwoven threads
(hyphae) making up the vegetative body of a fungus.

Degenerate bacteria that do not have cell walls. Mycoplasmas are smaller than bacteria but larger than viruses. They cause animal and human diseases.

See Phytoplasma.

A symbiotic association of a fungus with the roots of a plant.

The death or disintegration of cells and tissue accompanied by darkening to black or brown.

A chemical or physical agent that kills, inhibits, or protects against nematodes.

Generally microscopic tubular worms, usually
living free in moist soil, water, and decaying matter, or as
parasites of plants and animals.

Necessary; obliged. An obligate parasite is an
organism that can live only on living tissue.

a swelling or blistering on leaves and other plant parts under conditions of high moisture and restricted transpiration (see also edema).

Female egg cell of oomycete fungi.

A group of fungi that produce oospores such as
Pythium, Phytophthora, and Aphanomyces.

Thick-walled, sexually-derived resting spore of
oomycete fungi.

a pore; opening in the papilla or neck of a perithecium, pseudothecium, or pycnidium through which spores are released.

To survive over the winter period.

An organism that lives within or upon another living organism from which it derives nourishment and in which it may cause various degrees of injury.

The phenomenon of the growth of one organism, the parasite, at the expense of another, the host.

An entity capable of producing disease.

An entity's capacity for producing a disease.

a subdivision of a plant-pathogenic bacterial species defined by host range; pathovar for bacteria is equivalent to forma specialis for fungi.

The enzyme that breaks down pectic substances to simple carbohydrates.

A round to flask-shaped, thick-walled spore-case with an ostiole (pore) and containing asci.

Having flagella all over the outside of the cell.