ABSTRACT
The term toxin is used for a product of the pathogen, its host, or pathogen host interaction which even at very low concentration directly acts on living host protoplasm to influence disease development or symptom expression. Toxins are different from enzymes in that they do not attack structural integrity of host tissues but affect the metabolism of the host because the toxins will act on protoplast of the cell. According to the source of origin, toxins are divided into 3 broad classes namely, pathotoxins, vivotoxins and phytotoxins. A host-specific or host-selective toxin is a substance produced by a pathogenic microorganism that, at physiological concentrations, is toxic only to the hosts of that pathogen and shows little or no toxicity against nonsusceptible plants. Most host-specific toxins must be present for the producing microorganism to be able to cause disease. The primary target of the toxin seems to be the cell plasma membrane, where victorin seems to bind to several proteins.
