2I.C.A.R.
Plant Virus Research Station, Agricultural College Estate, Poona-411005.
1Paper presented at First All India Seminar on Citriculture held at Nagpur (Nov. 1972).
Tristeza is spread in orchards from tree to tree by 7 species of aphids. In India 6 of these—Toxoptera citricida, T. aurantii, Aphis gossypii, A. craccivora, Myzus persicae, and Macrosiphum (Dactinotus) compositae—have been established as vectors. The virus is transmitted in a non-persistent manner and is not retained by the aphids after moulting. More than one strain of the virus exists in nature. One mild strain has been observed to afford protection to Kagzi lime plants against infection by the severe strains.
Tristeza virus particles are 2000 mμ in length and 10–12 mμ, in diameter. The virus is believed to be restricted to phloem tissue only.
Rootstock trials carried out in different regions in the country have shown that the most widely used rootstock, rough lemon (Citrus jambhiri), failed in some areas and behaved miserably in others.
Finally, suggestions have been made to avoid tristeza virus in orchards.
