Pathologic race

An obsolete term meaning vertical pathotype. See also: Physiologic race. Pathology

The study of diseases. Plant diseases are studied by plant pathologists, sometimes called phytopathologists. Pathosystem

A subsystem of an ecosystem, and one that is defined by parasitism. A pathosystem normally involves the interaction between a population of one species of host, and a population of one species of parasite. In a plant pathosystem, the host species is a plant. The parasite is any species which spends a major part of its life cycle inhabiting, and drawing nutrients from, one host individual. The parasite may thus be an insect, mite, nematode, parasitic Angiosperm, fungus, bacterium, phytoplasma, virus, or viroid. However, herbivores which graze populations of plants are usually regarded as belonging to the wider concept of the ecosystem. See also: Continuous pathosystem, crop pathosystem, Discontinuous pathosystem, Heteroecious, and wild pathosystem. Pathotype

A sub-population of a parasite that is defined by a stated characteristic of parasitic ability. Thus vertical pathotype and Horizontal pathotype. See also: Pathodeme. Pattern

The basic unit of a system. A word is a pattern of letters; a molecule is a pattern of atoms, a wall is a pattern of bricks, and so on. A system is a pattern of patterns, and each pattern of patterns is called a systems level. Pea

See: Pisum sativum. Pea, pigeon

See: Cajanus cajan. Pea, winged

See: Psophocarpus tetragonobolus. Peach

See: Prunus persica.

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