ABSTRACT
For an effective disease management, the correct diagnosis of a disease based on the identification of its causal agent is very essential. The assessment of symptoms from the sample containing all the plant parts showing disease symptoms is stressed and described. Microscopic examination of diseased plants is given as it is extremely helpful for establishing bacterial nature of a disease because the bacterial streaming is found in almost all the bacterial diseases except the crown gall. Koch’s postulates are described to prove the pathogenicity of the causal agent.
The methods of isolation of bacteria and their identification based on morphological, physiological, and biochemical characteristics is given. The other techniques like serological techniques, namely, monoclonal antibodies, enzyme-linked immunosorbent assay, and flow cytometry; genomic techniques, namely, polymerase chain reaction, real-time (TaqMan®) PCR, DNA/RNA (dot/slot-blot) hybridization, and fluorescent in situ hybridization (FISH) using rRNA (rDNA) oligonucleotide probes; enrichment techniques, and use of bacteriophages, which are helpful in the identification of bacteria are also described. The importance of pathogenicity test is stressed as it is the most important step in the fulfillment of Koch’s postulates. The method to prepare the diagnostic report is given.
