Virus indexing:

• It is the process of detection of presence of virus in plants using various techniques.

Methods of virus indexing

a) Sap transmission test:

• Virus are taken from the test plant
• Grinding with a mortar or pestle
• Sap is smeared onto the leaf of an indicator plant.
• If virus present in the sap, the indicator shows symptoms of concerned virus.

b) Serological test/ ELISA test:

• Done based on antibody reaction.
• Add a drop of centrifuged sap from a test plant to a drop of antiserum
• If virus present precipitates because of presence of specific antibody in the blood.

c) DNA finger prints:

• Which exhibit no visible symptoms.

d) Visible symptoms