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Bacterial wilt of tomato

(Glossary - In order of appearance in the text)




Author: Patrice G. Champoiseau and Timur M. Momol of University of Florida
Reviewers: Caitilyn Allen of University of Wisconsin; Jeffrey B. Jones and Carrie Harmon of University of Florida
Publication date: September 12, 2008. Revised April 4, 2009
Project title: Ralstonia solanacearum race 3 biovar 2: Detection, exclusion, and analysis of a select agent pathogen
Supported by: The United States Department of Agriculture - National Research Initiative Program (2007-2010)


Solanaceous. The Solanaceae family, also known as the "nightshade" family, is a family of flowering plants, many of which are edible, while others are poisonous. The family includes the Datura or Jimson weed, eggplant, mandrake, deadly nightshade or belladonna, capsicum, potato, tobacco, tomato, and petunia.

Bacterium. A bacterium is a microscopic organism consisting of individual cells. Bacteria cause diseases in many host plants. They can survive on crop residue, seed, or in soil and water; they may be spread by plant or plant cuttings transfer, mechanical means, insects, and seeds.

Pathogens. A pathogen, or infectious agent, is a biological agent that causes disease or illness to its host. A number of different organisms can cause plant infectious disease. Among them are fungi, bacteria, viruses, nematodes or parasitic plants.

Strains. A strain is a genetic variant or subtype of a microorganism (for example virus or bacterium or fungus).

Species. A species is one of the basic units of biological classification. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. Each species is placed within a single genus.

Races. A race is formed by a group of bacterial strains that are differentiated based on the response on a set of host differentials.

Biovars. A biovar is a group of bacterial strains that are distinguishable from other strains of the same species on the basis of their physiological characteristics.

Endemic. Endemic, in a broad sense, can mean "belonging" or "native to", "characteristic of", or "prevalent in" a particular geography, area, or environment; native to an area or scope.

Symptoms. A symptom is a subjective evidence of disease or physical disturbance. It is an evident reaction by a plant to a pathogen, and is not necessarily visible. Different pathogens can induce similar symptoms.

Vascular bundles. Vascular, or conductive, bundles are responsible for long-distance transport of water and nutrients throughout the plant. Highly developed plants have two types of vascular tissues: the xylem and the phloem.

Xylem. The xylem is responsible for transportation of raw sap (water and nutrients) from roots to aerial parts of the plant. R. solanacearum is a limited xylem-invading pathogen.

Gram-negative. Bacteria have been classified as Gram-negative or Gram-positive regarding structural differences in their cell walls. Many species of Gram-negative bacteria are pathogenic. This pathogenic capability is usually associated with certain components of Gram-negative cell walls.

Aerobic. An aerobic organism requires oxygen for aerobic cellular respiration. Cellular respiration is the mechanism by which aerobic organism require oxygen to utilize substrates (for example sugars and fats) in order to obtain energy.

Bacterial colonies. On the surface of a solid growth medium, individual bacterial cells will grow and multiply to become visible bacterial colonies. All cells within the colony descend from a single ancestor and are identical. Characteristics of bacterial colonies (color, aspect, diameter or growth rate) are commonly used for bacteria identification.

Virulent. Virulence refers to the degree of pathogenicity of a microorganism, or in other words the relative ability of a microorganism to cause disease.

Selective medium. A growth or culture medium is a substance in which microorganisms, such as bacteria, or cells can grow. Selective media are used for the growth of only select microorganisms. They usually contain antibiotics to which the select microorganims is resistant to.

Variability. Variability here refers to variation of a given characteristic from one bacterial strain (or group of strains) to the other.

Species complex. R. solanacearum is considered a "species complex" as it includes individual isolates that may not be considered within a single species, as it is the case for the banana blood disease bacterium or Pseudomonas syzygii.

Carbohydrate substrates. Carbohydrates are simple organic compounds such as sugars and starch which contain carbon chains. They fill numerous roles in living organisms, such as the storage and transport of energy and structural components. Carbohydrates are differentially used as source of energy by bacteria.

Variation of DNA sequences. Comparison of DNA sequences is commonly used for classification studies of strains of microorganisms. It is basically assumed that the higher the homology is between two strains, the more closely related the strains are in terms of evolution. These types of studies are known as phylogenetic studies.

Phylotypes. A phylotype is defined as a group of strains that are closely related based on phylogenetic analysis of sequence data. Each phylotype is composed of a number of sequevars.

Sequevars. A sequevar, or sequence variant, is defined as a group of strains with a highly conserved sequence within the area sequenced.

Pathogenic. Pathogenicity is the ability of an organism to cause disease in another organism.

Root-knot nematode. Root-knot nematodes are plant-parasitic roundworms from the genus Meloidogyne. They exist in soil in areas with hot climates or short winters. There are a great many parasitic forms, including pathogens in most plants, animals, and also in humans.

Immunodiagnostic assays. These assays are based on the use of antibiotics in various test formats to detect and identify any molecules or cells (including bacteria). The most commonly used assays for bacteria detection and identification are agglutination, enzyme-linked immunosorbent assay (ELIZA), immunofluorescence, lateral flow strip tests and flow-through assays.

Antibodies. Antibodies (also known as immunoglobulins) are proteins that are used by the immune system to identify and neutralize foreign objects, such as bacteria and viruses. Due to their specificity, they are commonly used in biology for detection and identification of microorganisms.

Nucleic-acid. A nucleic acid is a molecule composed of nucleotide chains. These molecules carry genetic information. The most common nucleic acids are deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). Nucleic acids are universal in living things, as they are found in all cells and viruses.

DNA probe hybridization. DNA probe hybridization uses the ability of two complementary single-stranded nucleic acids to combine into a single molecule. Nucleotide probe of known sequence will be used to bind complementary strand of undetermined organism for identification.

Polymerase chain reaction (PCR) amplification. The polymerase chain reaction is a technique that consists of amplifying a DNA molecule exponentially.

Cultivars. A cultivar is a cultivated plant that has been selected and given a unique name because it has desirable characteristics (decorative or useful) that distinguish it from otherwise similar plants of the same species.

Biological control. Biological control is defined as the reduction of pest populations (including insects, mites, weeds and plant diseases) by natural enemies. Biological control agents of plant diseases are most often referred to as antagonists.

Suppressive soils. A suppressive soil is one that possesses some level of control of a disease forming organism. All soils have a natural level of disease suppressive activities. In most soils long term management can either reduce or increase this level of suppression.

Plant resistance inducer. Plant resistance inducers are natural or synthetic chemical compounds that apparently act by stimulating the natural defense response in the plant.


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