Cross-Protection Studies with Strains of Concave Gum and Psorosis Viruses

Abstract

Cross-Protection Studies with Strains o f Concave G u m and Psorosis Virusesphenomena in sweet orange seedlings infected with various California strains of psorosis virus, including concave gum, were first reported by Wallace ( 16, 17), who pointed out that in some instances protection was only partial. The cross-protection or virusstrain-interference reaction has sometimes been useful in diagnosing psorosis in cases where leaves of sweet orange seedlings failed to show definitive symptoms.I n 1960 an indexing test in the quarantine greenhouse used for the University of California Citrus Variety Improvement Program (9, 10, 18) revealed a faint oak-leaf pattern on leaves of King mandarin (Citrus nobilis Loureiro) inoculated with budwood of PI (Plant Introduction, U. S. Department of Agriculture) 209532, a sweet orange [C. sinensis

Elimination of Citrus psorosis virus using shoot tip grafting and electrotherapy techniques

“…PsA protects against a challenge from the more severe bark lesions induced by the more aggressive psorosis (PsB) (Wallace, 1957). Citrus psorosis disease is worldwide in many parts of the world, including South America and the Mediterranean areas (Roistacher, 1993). In Egypt, some investigators isolated and identified CPsV (Nour-Eldin, 1956;Nour-Eldin, 1957;Fahmy et al, 2002).…”

“…In addition, RT-PCR, the alternative detection method was applied by using several primers (Martin et al, 2004). Biological indexing could be performed for CPsV detection by graft-inoculating citrus in sensitive indicator plants such as sweet orange and then testing for cross-protection with severe isolate (PsB) (Roistacher and Calavan, 1965;Roistacher, 1993). A new method of biological indexing was organized for diagnosis of Citrus viruses and viroids by using indicator cutting as an alternative to seedlings (ElBacki et al, 2005;El Sayed, 2005;D'nghia et al, 2009).…”