Terminologies of plant pathology

Terminologies of
pathology
Kru’s biology

Plant Disease: A physiological disorder or structural abnormality that
is harmful to the plant or only it’s parts or products that reduced the
economic value.
Disorder: Non-infectious plant diseases due to abiotic causes such as
adverse soil and environmental conditions are termed disorders.
Disease Incidence : the number of plants affected by a disease within a
population. E.g. soil borne diseases, nematodes
Disease Severity : the measure of damage done by a disease. OR
Amount of disease present in a population. E.g. Leaf, stem, seed
diseases

Hypha (pl. Hyphae) : a single tubular thread-like filament of a fungal
mycelium. The hypha is the basic structural unit of a fungus.
Hyphae
Mycelium (pl. Mycelia) : a mass of hyphae that forms the body (thallus) of a
fungus.
Mycellium

Spore: a specialized reproductive body in fungi (and
some other organisms), containing one or more cells,
capable of developing into an adult.
Biotroph: an organism that can live and reproduce only
on another living organism. A biotroph is completely
dependent on the host organism as a source of nutrients,
i.e. it is an obligate parasite.

Necrotroph : an organism (parasite) that causes the death of host tissues as it grows through
them, obtaining its energy from the dead cells.
Saprophyte : an organism that obtains nourishment from non-living organic matter (usually
dead and decaying plant or animal matter) by absorbing soluble organic compounds.
Pathogenicity: The capacity of a pathogen to cause disease.
Pathogenesis : is the chain of events that lead to development of disease in the host (or)
sequence of progress in disease development from the initial contact between the pathogen
and its host to the completion of the syndrome.

Sign Symptom Syndrome
Sign: The pathogen or its parts or products seen on a host plant.
Symptom: The external or internal reactions or alterations of a plant as a result of a
disease.
Syndrome: The set of varying symptoms characterizing a disease are collectively
called a syndrome. OR The series of symptoms of a disease collectively known as
syndrome.

Virulence: The degree of pathogenicity of a given pathogen.
Virulent: Capable of causing a severe disease; strongly pathogenic.
Avirulent (non-virulent): Non-pathogenic or lacking virulence.
Infection: The establishment of a parasite within a host plant.
Latent Infection : where the host is infected with a pathogen but
does not show any symptoms.

Infectious disease: A disease that is caused by a pathogen which can
spread or transfer from a diseased to a healthy plant.
Non-infectious disease: A disease that is caused by an abiotic agent, that
is, by an environmental factor, not by a pathogen.
Inoculum: The pathogen or its parts that can cause infection. That portion
of individual pathogens that are brought into contact with the host.
Inoculum potential: Which consists of the number of propagules and their
capacity to cause infection.
Inoculate: To bring a pathogen into contact with a host plant or plant
organ.
Inoculation: The arrival or transfer of a pathogen onto a host.

Isolation: The separation of a pathogen from its host and its culture on a
nutrient medium.
Isolate: A single spore or culture and the subcultures derived from it.
Microscopic: Very small; can be seen only with the aid/use of a
microscope.
Penetration: The initial invasion of a host by a pathogen.
Primary infection: The first infection of a plant by the overwintering or
oversummering pathogen.
Primary inoculum: The overwintering or oversummering pathogen, or
its spores that cause primary infection.

Secondary infection: Any infection caused by inoculum produced as a
result of a primary or a subsequent infection. OR An infection caused
by secondary inoculum.
Secondary inoculum: Inoculum produced by infections that took place
during the same growing season.
Transmission: The transfer or spread of a pathogen from one plant to
another.
Culture: To artificially grow micro-organisms on a prepared food
material.
Immune: Cannot be infected by a given pathogen.
Resistant: Possessing qualities that hinder the development of a given
pathogen. OR Infected little or not at all.

Susceptible: Lacking the inherent ability to resist disease or attack by a
given pathogen; non-immune.
Tolerance: The ability of a plant to sustain the effects of a disease
without dying or suffering serious injury or crop loss.
Disinfectant: A physical or chemical agent that frees a plant, organ or
tissue from infection.
Disinfestant: The chemical agent that kills or suppress or inactivates
pathogens in the environment or on the surface of a plant or plant organ
before infection takes place.
Fungicide: Chemicals used to kill fungi OR A compound toxic to fungi.
Nematicides: A chemical compound that kills nematodes.

Bactericide: A chemical compound that kills bacteria.
Mycology: The study of fungi is called mycology. OR It is the science
which deals with the study of fungi is known as mycology.
Nematology: It is the science which deals with the study of nematodes.
Virology: It is the science which deals with the study of viruses.
Bacteriology: It is the science which deals with the study of bacteria.
Eradication : the control of plant disease by eliminating the pathogen after
it is established or by eliminating all of the plants that carry the pathogen.
Exclusion : a method of disease prevention in which the pathogen or
infected plant material is excluded from crop production areas. See
quarantine.

Quarantine : legal restriction of the transport of plants and/or plant
parts in order to prevent the spread of pests and pathogens.
Race : a subgroup of pathogens within a species that infect a given set
of plant varieties. Races may be distinguished from each other by
virulence or symptom expression but not by morphology.
Systemic : (1) pertaining to a disease in which the pathogen spreads
generally throughout the plant OR The growth of pathogen from the
point of entry to varying extents without showing adverse effect on
tissues through which it passes.; (2) pertaining to a chemical absorbed
into the plant through root or foliage and transported internally
throughout the plant.
Systemic fungicide: a chemical agent that spreads internally through
the plant and eradicates established fungal infections.

Vector: any living organism (e.g., insect, mite, bird, nematode, parasitic
plant, human, etc.) that transmits a pathogen from an infected organism
to an uninfected one.
Virus : a submicroscopic, non-cellular structure consisting of a core of
infectious nucleic acid (either RNA or DNA) within a protein coat.
Necrosis: Death of tissue, cells or organ is known as necrosis.
Phyllody: Floral part converted into leafy structure is called as
phyllody.
Hypertrophy: Excessive growth of host tissues due to increase in size
of affected organs or cells of a particular tissues.

• Necrosis Phyllody Hypertrophy

Hyperplasia: It is the abnormal increase in the size of a plant organ due
to increase in number of cells of which the organ is composed.
Appressorium: The swollen tip of a hypha or germ tube that facilitates
attachment and penetration of the host by the fungus.
Disease cycle: The chain of events as the transmission of pathogen,
attack on the host, infection, invasion of tissues and development and
reproduction of pathogen on the host to completing the process of
pathogenesis.
Antagonism: Injury, killing or inhibition of the growth of one species
of microorganism to another microorganism.
Antagonists: An organism having the capacity or ability to inhibit the
growth or interfere with the activity of another microorganism.

Antibiosis: Inhibition or destruction of one microorganism by a
metabolic products of another microorganism.
Competition: The ability of one organism to utilize a substrate more
efficiently than another microorganism.
Hyper parasitism: The parasitism of a parasite by another parasite.
(Rhizoctonia solani on Pythium spp., Fusarium maxima on Rust fungi).
Hypersensitivity: Excessive sensitivity of plant tissue to certain
pathogens. Affected cells are killed quickly blocking the advancement
of obligate parasite.
Adjuvants: The inert materials added to a fungicide to improve the
physical characteristics of the toxicant and its carrier. Most of them are
surface active agents and cause variations in surface tension.

Antibiosis Hyper parasitism
Competition Hypersensitivity

Compatibility: It is a combining ability of a chemical with each other
without any adverse effect.
Phytotoxicity: The capacity of a compound to produce injury to plant.
Tenacity: It is an ability of chemicals/pesticides for holding them on
plant surface.

Terminologies of plant pathology

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Terminologies of plant pathology