*University of Agricultural Sciences, Hebbal, Bangalore-560 024.
Indian Institute of Horticultural Research, Bangalore-560080.
Contribution No. 711 of Indian Institute of Horticultural Research, 255, Upjwr Palace Orchards, Eangalore-560 080.
Symptom observation together with that of back indexing tests revealed the normal behaviour of mild strains (M1 = Very mild; M2 = mild) on acid lime Citrus aurantifolia) trees under field condition for a period of over 5 years. Seedlings preimmunized with mild strains showed only mild leaf flecking symptoms on field trees and mild reactions on indexed acid lime seedlings. The severe strain continued its severe reactions both in the field and back indexed seedlings. While, trees previously inoculated with mild strain and later after 8 weeks challenge inoculated with severe strain showed only mild vein flecks on field trees and on acid lime indicator plants. Out of 8 uninoculated plants three each got severe and mild strains respectively, while two plants showed both mild and severe strains on the same plant but on different branches.
