Koch's postulates

German physician and bacteriologist Robert Koch in 1890 postulated a set of four criteria to determine the etiology of pathogenic diseases, so-called "Koch's postulates". Koch's postulates were based on the idea of Jakob Henle. Koch's postulates serve as a basic tool to test whether a pathogen is responsible for causing a disease. This is equally useful in testing the disease caused by culturable bacteria as well fungi.

Four criteria of Koch's postulates

  1. A microorganism must be present in the diseased plant, but not found in the healthy one.
  2. The microorganism must be isolated from the diseased plant and grown in pure culture.
  3. Inoculation of healthy plants with the cultured microorganism must develop the same disease.
  4. The microorganisms must be re-isolated and grown from the inoculated diseased plant and must be similar with the original microorganism.

Application of Koch's postulates

Being relatively simple, Koch's postulates have been serving the pathological laboratory since its formulation. In every laboratory dealing with plant pathology, Koch's postulates is one of the most important experiments being performed. Within three weeks a pathologist is able to identify the etiology and pathogenesis of the diseases in the plant. The isolated and re-isolated pathogen can be further utilized for developing its method of control.

Limitations of Koch's postulates

Koch's postulates have a major limitation as it can not be applied on unculturable microorganisms (biotrophs) including viruses and asymptomatic diseases.

Content first created on 28-04-2021
last updated on 18-08-2023