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A Necrotic Strain of Citrus Ringspot Virus and Its Relationship to Citrus Psorosis Virus. L. W. Timmer, Associate Professor, Texas A&I University Citrus Center, Weslaco, Texas 78596; Phytopathology 64:389-394. Accepted for publication 9 October 1973. DOI: 10.1094/Phyto-64-389.

A necrotic strain of citrus ringspot virus (CRSV-NS) was found in nucellar grapefruit trees (Citrus paradisi) in South Texas. Field symptoms observed were: flecking of young leaves, shoot necrosis, chlorotic flecks, spots, blotches, and distortion on older leaves. Mature leaf symptoms and twig lesions similar to those produced by psorosis were observed on some trees infected with CRSV-NS. Graft inoculation of seedlings of many citrus species and cultivars produced symptoms similar to those observed in the field. Graft inoculation of the peduncles of young grapefruit with rampant psorosis induced gum-impregnated spots surrounded by halos, but inoculation with CRSV-NS caused sunken chlorotic spots. Previous inoculation of ‘Key’ lime seedlings (C. aurantifolia) with psorosis virus protected them against the severe symptoms normally induced by CRSV-NS. Graft inoculation of seedlings with bark from some nucellar grapefruit trees with rampant psorosis bark lesions induced symptoms similar to those of CRSV-NS. CRSV-NS is probably a strain of the citrus psorosis virus complex.