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Etiology

Partial Characterization of a Virus Associated with Citrus Ringspot. K. S. Derrick, University of Florida, Institute of Food and Agricultural Sciences, Citrus Research and Education Center, Lake Alfred 33850; R. H. Brlansky(2), J. V. da Graca(3), R. F. Lee(4), L. W. Timmer(5), and T. K. Nguyen(6). (2)(4)(5)(6)University of Florida, Institute of Food and Agricultural Sciences, Citrus Research and Education Center, Lake Alfred 33850; (3)University of Natal, Pietermaritzburg, South Africa. Phytopathology 78:1298-1301. Accepted for publication 28 April 1988. Copyright 1988 The American Phytopathological Society. DOI: 10.1094/Phyto-78-1298.

Infectivity of citrus ringspot virus (CRSV) was associated with two components that were readily separated by sucrose density gradient centrifugation. An antiserum, prepared to a partially purified preparation of the virus, was used to assay gradient fractions and crude extracts by serologically specific electron microscopy (SSEM). A mixture of short (300500 nm) and long (1,500-2,500 nm), extremely flexible, filamentous particles was observed in extracts of infected tissue. Examination of the top and bottom fractions from gradient centrifugation that contained the infectious components revealed the short particles were concentrated in the top fractions, and the long particles were in the bottom fractions. The short and long particles were approximately 10 nm in diameter and appeared identical, except for difference in length; conceivably, they each contain a portion of the CRSV genome. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of preparations of CRSV, partially purified by gradient centrifugation and agarose gel electrophoresis, were found to contain a protein with a molecular mass of about 48 kilodaltons (kd) that was not found in comparable preparations from noninfected leaves. Because the 48-kd protein was associated with fractions that contained the infectious components and the short and long particles and was not present in preparations of healthy tissue, it appears to be viral and may function as a coat protein.