Copy of `Introductory Plant Pathology`

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Introductory Plant Pathology Category: Sciences > Biology Date & country: 05/06/2008, CA Words: 61

Avirulence genes
avirulence genes are believed to govern the production of elicitors ligands which can be recognized by receptors encoded by host resistance genes and cause a plant pathogen or pest to elicit a resistance response in a host plant.

Avirulent
lacking virulence.

Biotroph
an organism that can live and multiply only on another living organism.

Conjugation
it occurs when two compatible bacteria come in contact with one another and a small portion of the chromosome or plasmid from one bacterium is transferred to the other through a conjugation bridge or pilus.

Cork layerperiderm
An external, secondary tissue impermeable to water and gases. It is often formed in response to wounding or infection

Cytoplasmic resistance
Corn cytoplasmic resistance against the southern corn leaf blight.

Disease Escape
the failure of a host to become diseased because of separation, in space or time, of susceptible host tissues and the infective units of the pathogen.

Disease Stages-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.

Disease triangle
a concept describing the simultaneous occurrence of a pathogen, a susceptible host, and a favorable environment such that a disease may develop.

Elicitors
compounds of the pathogen that the plant senses to initiate defense reactions; elicitors can be divided into enzymes and compounds without catalytic activity

Facultative parasite
an organism that is usually saprophytic but may become parasite.

Facultative saprophyte
an organism that is usually parasitic but may live as a saprophyte having the ability to be a parasite.

Free radicals
Active oxygen species (AOS), a collective term for radicals and other nonradical but reactive species derived from oxygen, including O-, HO- and H2O2.

Hemibiotrophic
a microorganism that parasites in living tissues for a period and continues its life cycle on dead tissues.

Heterokaryosis
the condition of being a heterokaryon Gr. heteros=different from, karyon=nucleus, -- a cell that contains genetically different nuclei or a thallus made up of such cell. Cf. dikaryon, homokaryon

Heteropoidy
a condition in which a cell, tissue, or organism that contains more or few chromosomes per nucleus than the normal 1N or 2N for that organism.

Host
a living organism from which parasites or pathogens obtain nutrients.

Host range
the various kinds of host plant that may be attacked by a pathogen.

Host recognition
Recognition determines the specificity of host-parasite interaction, following by a compatible or incompatible relationship.

Hypersensitive reaction
Excessive sensitivity of plant tissues to certain pathogens. Affected cells are killed quickly, blocking the advance of obligate parasites

Incubation period
the time interval between inoculation and appearance of disease symptoms.

Induced resistance
(Acquired resistance) Induced resistance develops after a primary infection (or treatment with certain chemicals) and its effective against a second infection. This phenomenon resembles acquired immunity in animals.

Infection
the establishment of parasite within a host plant.

Inoculation
The arrival or transfer of a pathogen onto a host.

Inoculum
the pathogen or its parts that come in contact with a host and can cause disease.

InvasionColonization
The spread of a pathogen into the host.

Latent infection
the state in which a host is infected with a pathogen but does not show any symptoms.

Life cycle
the stage of successive stages in the growth and development of an organism that that occur between the appearance and reappearance of the same stage of organism.

Local infection
infection involves a single cell, afew cells, or a small area of the plant.

Mutation
a change in the nucleotide sequence of DNA; the ultimate source of genetic diversity.

Necrosis
most commonly defined as cell death that does not require the active participation of the cell in its own demise.

Necrotroph
a microorganism feeding only on dead organic tissue.

Non-Host Resistance
inability of a pathogen to infect a plant because the plant is not a host f the pathogen due to lack of something in the plant that the pathogen needs or to the presence of substances incompatible with the pathogen plants are outside the host range of pathogens.

Obligate parasite
a parasite that in nature can grow and multiply only on or in living organisms.

Papilla
A nipple-like structure deposited beneath the cell wall on the inside of a cell being attacked by a fungus, apparently serving as a defense mechanism against infection.

Parasite
an organism or virus that lives on or in another living organism and obtains food from that organism.

Pathogenesis
the sequence of processes in disease development from the time of infection to the final reaction in the host; production and development of disease.

Pathogenicity
the capability of a pathogen to cause disease.

Penetration
In relation to diseases, the initial invasion of a host by a pathogen.

Phytoalexins
low molecular weight antimicrobial compounds that are both synthesized by and accumulated in plants which have been exposed to microorganisms

PR-1
unknown [Rauscher M, Adam AL, Wirtz S, Guggenheim R, Mendgen K, Deising HB., 1999. PR-1 protein inhibits the differentiation of rust infection hyphae in leaves of acquired resistant broad bean.

PR-2
beta-1,3-glucanase

PR-3
chitinase

PR-5
thaumatin-like protein [Ibeas JI, Lee H, Damsz B, Prasad DT, Pardo JM, Hasegawa PM, Bressan RA, Narasimhan ML, 2000. Fungal cell wall phosphomannans facilitate the toxic activity of a plant PR-5 protein.

Prepenetration phenomena
attachment, germination and differentiation.

Primary infection
infection caused by primary inoculum.

Primary inoculum
the overwintering or oversummering pathogen, or its spores that cause primary infection.

Programmed Cell Death
(PCD) activation of genetically regulated cell suicide machinery.

Saprophyte
an organism that can obtain nutrients from dead organic material.

Secondary infection
infection caused by secondary inoculum.

Secondary inoculum
inoculum produced by infections that took place during the same growing season.

Species L. spcies= a kind
Of sexually reproducing organisms, one or more natural populations in which individuals are interbreeding and are reproductively isolated from other such groups.

Symbiosis
a mutually beneficial association of two or more different kinds of organisms.

Systemic infection
A plant pathogen occurs throughout the plant.

The Gene-for-Gene Concept
A single plant-resistance gene reacts with the matching single avirulence gene of a pathogen.

Tolerance
the ability of a plant to sustain the effects of a disease without dying or suffering serious injury or crop loss. Also, the amount of toxic residue allowable in or on edible plant parts under the law.

Transduction
a bacterial virus phage transfers genetic material from the bacterium in which the phage was produced to the bacterium it infects next.

Transformation
bacterial cells are transformed genetically by absorbing and incorporating in their own cells genetic material secreted by, or released during rupture of, other bacteria.

Tylosis
An overgrowth of the protoplast of a parenchyma cell into an adjacent xylem vessel or tracheid

Virulence
the degree of pathogenicity of a given pathogen.

Virulent
capable of causing a severe disease; strong pathogenic.