Plant Pathologhy

pertaining to the absence of life, as diseases not caused by living organisms

insufficient soil water for normal plant growth

injury of plant tissues burned or scorched by direct sun or or sunburn

injury of a plant part by abrasion, mutilation, or wounding

to fall over

• an element needed in relatively large quantities for plant growth, e.g.
• nitrogen (N), phosphorus (P), and potassium (K); (see micronutrient)

an essential element needed by plants for growth and required in very small amounts (see macronutrient)

transfer of pollen from anther to stigma or from a staminate cone to an ovulate cone

any air contaminant that causes undesirable effects on living organisms or materials

• air pollutant that must be chemically produced from other air pollutants,
• e.g. ozone (O3) that is a product of a photochemical reaction
• of exhaust products from combustion engines in the atmosphere

chemical reactions that require sunlight

pertaining to symptoms that develop suddenly(see chronic)

pertaining to slow-developing, persistent, or recurring symptoms (see acute)

• a secondary air pollutant formed when the exhaust of automobiles and
• other internal combustion engines is in the presence of sunlight

• a primary air pollutant produced in industrial processes and coal
• burning that causes interveinal necrosis on broadleaf plants and tip
• necrosis on conifers

primary air pollutants produced from internal combustion engines and other industrial processes

• air pollutant that is released directly into the atmosphere and is
• harmful to plants, e.g. SO2 or NOx

• precipitation (fog, rain, snow) with a low pH, due to the presence of
• nitric and sulfuric acid formed by the reaction of air pollutants (N0x and S02) with water

• combination of biotic factors (e.g. insect pests, pathogens) and
• abiotic factors (e.g. drought, air pollution) that contributes to poor
• growth and death of populations of trees

a plant hormone influencing various aspects of vegetative growth, fruit ripening, abscission of plant parts,and the senescence of flowers

• a common pollutant from volcanoes and several industries such as brick
• factories, aluminum smelters, and phosphate fertilizer factories.

a chemical used for killing plants or inhibiting plant growth, e.g. a weed or grass killer

movement of airborne particles of a spray, dust, or vapor away from the target area during or shortly after an application

indication of disease by reaction of the host, e.g. canker, leaf spot, wilt (see sign)

wilt due to insufficient soil water from which a plant can recover when water is supplied

any symptom that suggests the action of flame or fire on the affected part, often seen at the margins of leaves

elongation of stems caused by reduced light intensities

foliar necrosis, often marginal, of plants that retain their leaves in winter due to water deficiency because they cannot take up water from frozen soils

a distinguishing characteristic important for the identification of a disease or other condition

death of cells or tissue, usually accompanied by black or brown darkening

death of a seedling before or shortly after emergence due to decomposition of the root and/or lower stem; it is common to distinguish between preemergence damping-off and postemergence damping-off

movement or growth of an organism in response to changing concentration of a chemical stimulus, often in relation to food or for mating chemotherapy

a plant disease lesion typically restricted in development in the leaf after reaching a characteristic size

necrotic area of tissue irregular in form

sudden, severe, and extensive spotting, discoloration, wilting, or destruction of leaves, flowers, stems, or entire plants

disease symptom caused by fungi resulting in premature drop of needles

large populations of bacteria that exude from the cut surface of infected plant tissue when observed with a microscope

erumpent, cushionlike fruiting body bearing conidiophores, conidia, and sometimes setae

an asexual, nonmotile fungal spore that develops externally or is liberated from the cell that formed it

disease symptom characterized by non-uniform coloration, with intermingled normal, light green and yellowish patches, usually caused by a virus; often used interchangeably with mottle

disease symptom comprising light and dark areas in an irregular pattern,usually caused by a virus; often used interchangeably with mosaic

disease symptom characterized by yellowish or necrotic rings enclosing green tissue, as in some plant diseases caused by viruses

symptom of virus disease in which regions along veins are darker green than tissue between veins

a white, powdery, superficial ascomycetous fungus that is an obligate parasite and generally is found only on one or a few closely related species of plants

a plant disease in which the fungus appears as a downy growth on the host surface; caused by a member of the oomycetes

an organism that can live and multiply only on another living organism (see necrotroph)

sexual spore borne in an ascus

non-motile, asexual spore that is borne in a sporangium

saclike fungal structure in which the entire contents are converted into an indefinite number of asexual spores

a disease caused by a specialized group of basidiomycetes that often produces spores of a rusty color

one of two kinds of plant on which a parasitic fungus (e.g. rust) must develop to complete its life cycle

a rust fungus that typically exhibits all five stages of the rust life cycle (see demicyclic, microcyclic)

a rust fungus that lacks the urediniospore (repeating) stage (e.g. many species of Gymnosporangium) (see macrocyclic, microcyclic)

describing a rust fungus that produces only teliospores and basidiospores (see demicyclic, macrocyclic)

in reference to rust fungi, producing all spore forms on one species of host plant (see heteroecious)

common name usually used for diseases caused by oomycetes in the genus Albugo

a disease caused by a smut fungus (Ustilaginales) in the Basidiomycota or the fungus itself; it is characterized by masses of dark brown or black, dusty to greasy masses of teliospores that generally accumulate in black, powdery sori

a xylem disease that disrupts normal uptake of water and minerals, resulting in wilting and yellowing of foliage

isolated, wilted or necrotic branch with dead leaves attached

in reference to prokaryotic organisms, having special growth and nutritional requirements

plant-parasitic pleomorphic mollicute (prokaryote with no cell wall) found in phloem tissue; cannot yet be grown on artificial nutrient media

a plant disease characterized (in woody plants) by the death of cambium tissue and loss and/or malformation of bark, or (in non-woody plants) by the formation of sharply delineated, dry, necrotic, localized lesions on the stem; "canker" may also be used to refer to the lesion itself, particularly in woody plants

to circle and cut through a stem or the bark and outer few rings of wood, disrupting the phloem and xylem

abnormal swelling or localized outgrowth, often roughly spherical, produced by a plant as a result of attack by a fungus, bacterium, nematode, insect, or other organism

abnormal increase in the size of cells in a tissue or organ, often resulting in the formation of galls or tumors

abnormal increase in the number of cells, often resulting in the formation of galls or tumors

a circular, self-replicating hereditary element that is not part of a chromosome; plasmids are used in recombinant DNA experiments as acceptors and vectors of foreign DNA

fungal development primarily over the root surface

type of wood decay resulting from enzymatic action of fungi; it degrades all components of wood, including lignin, leaving the wood light-colored and spongy

wood decay resulting from selective removal of cellulose and hemicellulose, leaving a brown amorphous residue that usually cracks into cubical blocks and consists largely of slightly modified lignin

poisonous compound produced by a fungus

chemical byproduct from Aspergillus flavus and A. parasiticus harmful to humans and other animals

a vegetative resting body of a fungus, composed of a compact mass of hyphae with or without host tissue, usually with a darkened rind

process in which an organism enters, invades, or penetrates and establishes a parasitic relationship with a host plant

to attack as a pest (used especially of insects and nematodes); to contaminate, as with microorganisms; to be present in large numbers

an organism that maintains its population in soil over a period of time

an organism whose population in soil diminishes in several months to years

site in or on a host plant where infection can occur

structure composed of two guard cells and the opening between them in the epidermis of a leaf or stem, functioning in gas exchange

epidermal leaf structure specialized for secretion or exudation of water; leaf opening at terminus of vein

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

injuries to plant tissues that often breach barriers (cuticle, bark, cell walls) that might otherwise exclude pathogens; some pathogens (e.g. viruses) can enter plants only through a wound; wounds may occur from natural growth processes, physical and chemical agents, animals (especially insects), and many human agricultural activities, such as pruning

leaf surface

the calm layer of air on surfaces below the layer of more turbulent air

microenvironment in the soil, immediately around plant roots

process used to free soil of selected harmful microorganisms using heat

a living organism (e.g., insect, mite, bird, higher animal, nematode, parasitic plant, human) able to carry and transmit a pathogen and disseminate disease; (in genetic engineering) a vector or cloning vehicle is a self-replicating DNA molecule, such as a plasmid or virus, used to introduce a fragment of foreign DNA into a host cell

the departure of the average daily temperature from a defined base (e.g.the minimum recognized temperature for the growth of a plant species). The number of degree-days may be totaled to assess the accumulated warmth of a particular year's growing season.

inhibition of fungal growth, sporulation, or spore germination but not death; used to describe the nonspecific phenomenon in natural soils where spore germination is inhibited and often overcome by rhizosphere nutrients

swollen, flattened portion of a fungal filament that adheres to the surface of a higher plant, providing anchorage for invasion by a fungus

the specialized, narrow, hyphal strand on the underside of an appressorium that penetrates host cells

the specialized, narrow, hyphal strand on the underside of an appressorium that penetrates host cells

stalked, thick-walled, lobed cells that stick to plant surfaces; sometimes used to describe the infection structures produced by ectotrophic hyphae of certain root-infecting fungi such as Gaeumannomyces (take-all pathogen)

specialized branch of a parasite formed inside host cells to absorb nutrients

penetration of plant tissues by a pathogen through barriers such as leaf cuticle by chemical and physical means (e.g. penetration peg)

penetration of plant tissues by a pathogen through natural openings (e.g. stomata) or wounds

the time between penetration of a host by a pathogen and the first appearance of disease symptoms; the time during which microorganisms inoculated onto a medium are allowed to grow

the time between infection and the production of new inoculum; the time after a vector has acquired a pathogen and before it can be transmitted

protein that catalyzes a specific biochemical reaction

outside a cell

carbohydrate polysaccharide composed of glucose units; major component of plant primary cell wall

a methylated polymer of galacturonic acid found in the middle lamella and the primary cell wall of plants; jelly-forming substance found in fruit

a chemical substance produced in one part of an organism and transported in minute quantities to induce a growth response in another part, e.g. in plants, auxins, cytokinins, and gibberellins

plant hormone (growth regulator) influencing growth through cell elongation

plant hormones (growth regulators) that control cell division and are important for shoot stimulation of callus in tissue culture

plant hormones (growth regulators) that affect stem elongation

a plant hormone influencing various aspects of vegetative growth, fruit ripening, abscission of plant parts, and the senescence of flowers

the shedding of leaves or other plant parts as the result of physical weakness in a specialized layer of cells (the abscission layer) that develops at the base of the structure

a compound produced in microbes (e.g., mycotoxins, syringomycins) or plants (e.g., caffeine or nicotine) that is not necessary for normal growth and development

produced in response to a stimulus

nipple-like projection; used to describe the tip of some sporangia and the localized wall thickenings on the inner surface of plant cell walls at sites penetrated by fungi

amorphous, hardened carbohydrate constituent of plant cell walls, commonly developing upon injury

balloonlike extrusions of parenchyma cells into lumina of contiguous vessels that partially or completely block them

gelatinous, sugary aggregate that is synthesized and exuded by plant tissues

external protective tissue of a stem or root, impermeable to water and gasses; the primary component of bark

symptom in which small lesions fall out of leaves, giving the leaf the appearance of being hit by buckshot

substance produced in higher plants in response to a number of chemical,physical, and biological stimuli that inhibits the growth of certain micro-organisms

rapid and localized cell death at the site of infection in resistant interactions between plants and pathogens

reduced disease symptoms on a portion of a plant distant from the area where the inducing agent is active, caused by the triggering of active plant defenses against a variety of pathogens; used to describe increased resistance in plants induced by certain rhizobacteria

a molecule produced by the host (or pathogen) that induces a response by the pathogen (or host)

possessing properties that prevent or impede disease development (see susceptible)

prone to develop disease when infected by a pathogen (see resistance)

degree or measure of pathogenicity; relative capacity to cause disease

the hypothesis that corresponding genes for resistance and virulence exist in the host and pathogen, respectively

resistance which is effective against some biotypes or races of the pathogen, but not others, usually inherited monogenically and expressed qualitatively.

determined by a single gene

resistance which is effective against some biotypes or races of the pathogen, but not others, usually inherited monogenically and expressed qualitatively

resistance which is effective against all biotypes of the pathogen

the process whereby a normally susceptible host is infected with a less virulent pathogen (usually a virus) and thereby becomes resistant to infection by a second, usually related, more virulent pathogen

living cell exclusive of a wall

the development of genetically modified organisms through the use of modern technology and processes, including genetic engineering

organism possessing a gene from another species; used to describe the organisms that have been the subject of genetic engineering