Virus Indexing - It may be emphasized that all the plants obtained through meristem culture, with or without chemo or thermotherapy, are not virus-free. Therefore, such plants have to be tested for the presence of the concerned virus (es); this is called virus indexing.

(1) The simplest method for virus indexing is to score the plants for the presence of specific symptoms produced by the relevant virus. However, the development of visible symptoms may take considerable time.

(2) Alternatively, the saps from test plants may be used to inoculate highly sensitive and healthy indicator plants. An indicator plant for a virus is that plant species or variety, which is highly susceptible to the virus and readily develops the symptoms.