Glossary of phytopathology

Phytopathology is the study of plant diseases. It is a multi-disciplinary science since prerequisites for disease development are the presence of a susceptible host species, a pathogen and the appropriate environmental conditions. This is known as the disease triangle. Because of this interaction, the terminology used in phytopathology often comes from other disciplines including those dealing with the host species ( botany / plant science, plant physiology), the pathogen (bacteriology, mycology, nematology, virology), the environment and disease management practices (agronomy, soil science, meteorology, environmental science, ecology, plant breeding, pesticides, entomology), and areas of study that apply to both the host and pathogen (molecular biology, genetics, molecular genetics). The result is that most phytopathological glossary include terms from these other disciplines in addition to terms (disease incidence, horizontal resistance, gene-for-gene relationship, blast, scab and so on) that are specific to, or which have a unique meaning in phytopathology. This glossary is no exception. However, for the sake of brevity, it has, for the most part, restricted terms from other disciplines to those that pertain to the pathogen. At some point, these terms should be moved to other glossaries (e.g. glossary of mycology, glossary of nematology, and so on).

The Actinobacteria or Actinomycetes are a group of Gram-positive bacteria.
The Division Basidiomycota is a large taxon within the Kingdom Fungi that includes those species that produce spores in a club-shaped structure called a basidium.
A chlamydospore is the thick-walled big resting spore of several kinds of fungi.
Diploid (2x) cells have two copies (homologs) of each chromosome, usually one from the mother and one from the father.
The epidemic condition of a disease, in a plant population. Compare with enphytotic

general resistance (syn. horizontal resistance, race non-specific resistance)
Gram-negative bacteria are those that do not retain crystal violet dye in the Gram staining protocol.
Gram-positive bacteria are classified as bacteria that retain a crystal violet dye during the Gram stain process.

horizontal resistance (syn. general resistance, race non-specific resistance)
hypovirulence is reduced virulence of a pathogen. Hypovirulence in fungi can be caused by a virus within the fungus. The virus reduces virulence and sporulation. A hypovirus-fungus can be used in biological control.
Mycelium is the vegetative part of a fungus consisting of a mass of branching, threadlike hyphae that exists below the ground or within another substrate.
A nematicide is a type of chemical pesticide used to kill parasitic nematodes.
Nematodes are unsegmented, bilaterally symmetric and triploblastic protostomes with a complete digestive system.

race non-specific resistance (syn. general resistance, horizontal resistance)
A saprotroph (or saprobe) is an organism that obtains its nutrients from non-living organic matter, usually dead and decaying plant or animal matter, by absorbing soluble organic compounds.
A sclerotium is a compact mass of hardened mycelium (as an ergot) stored with reserve food material that in some higher fungi becomes detached and remains dormant until a favorable opportunity for growth occurs.

spiroplasma - helical, motile, cell wall-less bacterium; member of genus Spiroplasma in class Mollicutes
Teliospore (sometimes called teleutospore) is the thick-walled resting spore of some fungi (rusts and smuts), from which the basidium arises.
A virus is a microscopic particle (ranging in size from 20 - 300 nm) that can infect the cells of a biological organism.
A zoospore is a motile asexual spore utilizing a flagellum for locomotion.
A zygospore is a sexual part of a fungus, a chlamydospore that is created by the nuclear fusion of haploid hyphae of different mating types.