Glossary

A

abiotic: non-living, or a condition caused by a non-living agent (e.g. cold temperature, nutrient deficiency)

ascospore: a sexually-produced fungal spore; specific to the fungal lineage Ascomycota

asexual: lacking sexual characteristics, or reproduction without the union of male and female gametes (or two distinct organisms)

B

bacterium (pl. bacteria): microscopic, single-celled organisms lacking a nucleus or membrane-bound organelles and reproducing asexually; morphology usually spherical, spiral, or rod shaped; ubiquitous in every habitat on Earth, including soil, water, organic matter, and in/on the bodies of plants and animals

bud: a.) a small lateral or terminal projection on the stem of a plant, often enclosed by protective scales, from which shoots, leaves, or flowers develop b.) an undeveloped shoot, leaf, or flower c.) an outgrowth from an organism that creates a new individual (asexual reproduction)

C

chlorophyll: a group of green pigments found in all plants that are vital for the process of photosythesis, allowing plants to obtain energy from light

chlorosis: an abnormal yellowing or whitening in green plant tissue due to insufficient chlorophyll production

chlorotic tissue: plant tissue that has lost its normal green coloration

columella: Any small columnlike structure in various plants and animals, often forming the central axis of development for the organism or an anatomical structure.

conidia (singular: conidium): asexual, non-motile, fungal spores; when dispersed, they develop into organisms genetically identical to the parent (clone)

conidiophore: a specialized fungal hypha that produces conidia.

cultivar: deliberately selected variants within a cultivated species that are grown for horticultural and/or agricultural advantages

D

dieback: progressive death of shoots, branches, and roots that generally begins at the tip and works back to the main body of the plant

disease cycle: the chain of events involved in disease development, including the stages of development of the pathogen and the effect of the disease on the host

F

fruiting body: a reproductive structure produced by some fungi that is distinct in size, shape, and coloration for each species and contains spore-producing structures; part of the sexual phase of a fungal life cycle (also known as a sporocarp)

G

gum: complex polysaccharidal substances formed by plant cells in reaction to wounding or infection

H

host: an organism that is infected with or fed upon by a pathogenic or parasitic organism

host range: the various species or cell types that can act as a host to a particular parasite or pathogen

hyphae (sing. hypha): the fine, branching tubes which make up the body (or mycelium) of a multicellular fungus.

I

inoculum: a.) the pathogen or its part that causes infection of the host b.) small amount of a microorganism that is transferred to a substrate or a culture medium in order to propagate it

L

latent infection: a state in which a host is infected with a pathogen but does not show any symptoms

lesion: any defined area of living tissue that has been structurally modified as a result of a disease or damaging process

M

mottle: an irregular pattern of indistinct light and dark areas

mutation: a change in any portion of the genetic material that causes a permanent structural alteration of the DNA, frequently resulting in the appearance of a new characteristic in an individual; usually detrimental, but may be beneficial or neutral

mycelium: mass of hyphae that constitutes the vegetative parts of a fungus (the conspicuous part in most cases is the fruiting body of fungi).

N

necrotic: a cell, group of cells, or tissue that has suffered a rapid destruction and quick death; typically localized and may be caused by injury, radiation, chemicals, toxic substances, or microbiological interactions

O

oil gland: special glands of the leaf and fruit that produce essential oils

P

parasite: an organism that lives on or in another organism (the host), obtaining nourishment and shelter from the host; the host is often harmed and never benefits from the presence of the parasite, but is rarely killed

pathogen: an organism, usually a microorganism, which causes disease by intimate association with its host

pathovar (pv.): bacterial strain or set of strains with the same or similar characteristics, but differing in the species they infect or symptoms they produce; pathovars are below the species rank taxonomically

phialide: an open-ended, tubular or flask-like conidiophore that produces phialoconidia.

phialoconidia: (sing. phialoconidium): a conidium that develops from a phialide.

phloem: the plant vascular tissue that conducts products of photosynthesis and other organic molecules such as hormones throughout the plant body

pycnidium (pl. pycnidia): asexual fruiting body of certain fungi, generally spherical or inversely pearshaped, with an internal cavity containing conidia

R

rootstock: a living plant, sometimes just the stump, with a healthy, established root system, used for grafting a cutting or budding from another plant; the grafted portion is called the scion

S

scab: rough, crust-like, diseased or injured area on the surface of a plant

scion: young shoot or twig of a plant that is grafted onto the rootstock of another plant, usually a related species

shot-hole: symptom in which small diseased fragments of leaf tissue, usually dead, drop out of the lesion, leaving small holes in their place

spore: a.) small, walled reproductive body produced by non-flowing plants, algae, fungi and some protozoans; usually microscopic and resistant to desiccation and heat b.) dormant, nonreproductive body formed by certain unicellular organisms, especially bacteria, in response to harsh environmental conditions

systemic: spreading internally throughout the plant body; may refer to a pathogen or chemical

T

tolerance: ability of a plant to sustain the effects of a disease or damaging agent without dying or suffering serious injury or crop loss

V

variety: a taxonomic category, a subdivision of species, consisting of naturally occurring or selectively bred populations or individuals that differ from others of the same species in certain minor but heritable traits

vector: an organism that does not cause diseases itself but which carries the disease-causing microorganism from one host to another

W

witches' broom: the broom-like growth or massed proliferation formed by the dense clustering of branches of woody plants

X

xylem: the plant vascular tissue that conducts water and dissolved minerals upwards from the roots to the rest of the plant