Rapid Diagnosis of Citrus Tristeza Virus Infections by Sodium Dodecyl Sulfate-Immunodiffusion Procedures

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Abstract
An antiserum to sodium dodecyl sulfate (SDS)-degraded citrus tristeza virus (CTV) coat protein was efficiently produced by toe-pad injection of a rabbit. This serum reacted in SDS agar gel double-diffusion tests to extracts of citrus hosts infected with biologically different CTV isolates. The serum did not react to extracts of healthy citrus or extracts of citrus infected with other viruses. Purified CTV could be detected at concentrations as low as 1-2 .mu.g/ml. Detectable amounts of CTV were found in most phloem-containing vegetative tissues, but the highest titer was consistently found in young shoot bark. Virus titer was highest in young tissues and declined, often quite rapidly under warm conditions, as tissues matured. Virus could be concentrated from aqueous extracts by precipitation with 6% polyethylene glycol 6000 and centrifugation. Tissue could be stored frozen, lyophilized, or air dried for testing. Results obtained from SDS-immunodiffusion tests of 120 field trees correlated well with indexing results obtained from graft inoculation of Citrus aurantifolia ''Mexican'' lime indicators. The SDS-immunodiffusion procedure provides a simple, rapid approach to CTV identification applicable to both research and practical needs.