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Identification and Characterization of a Potexvirus from California Barrel Cactus. S. Attathom, Department of Plant Pathology, University of California, Riverside, CA 92521; L. G. Weathers(2), and D. J. Gumpf(3). (2)(3)Department of Plant Pathology, University of California, Riverside, CA 92521. Phytopathology 68:1401-1406. Accepted for publication 24 April 1978. Copyright © 1978 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-68-1401.

A rod-shaped virus, 520 nm long was isolated from California barrel cactus plants, Ferrocactus acanthodes, showing severe external symptoms. The virus was transmitted to and maintained in Chenopodium quinoa plants for purification and characterization. The purification procedure included clarification with butanol, precipitation with polyethylene glycol, and differential centrifugation. Purified virus had a maximum ultraviolet absorption at 260 nm, a minimum at 246 nm, and an A260/280 ratio of 1.26. One infectious, single-stranded RNA species was isolated from purified virus preparations. The molar percentages of nucleotides in the viral nucleic acid were A = 26.4, C = 29.2, G = 20.8, and U = 23.6. The coat protein had 216 amino acid residues, electrophoresed as a single component in SDS-polyacrylamide gels, and its molecular weight was estimated at 22,000. The virus reacted with antisera against Chessinís isolate of cactus virus X and d-protein of potato virus X. Ultrastructure of infected C. quinoa and Amaranthus caudatus leaves revealed abundant large aggregates of flexuous virus particles. It is concluded that this virus is a strain of cactus virus X.