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Physiology and Biochemistry

Comparison of Two Strains of Kalanchoe Latent Virus, Carlavirus Group. S. S. Hearon, Research plant pathologist, Florist and Nursery Crops Laboratory, USDA, ARS, BARC-West, Beltsville, MD 20705; Phytopathology 74:670-676. Accepted for publication 4 February 1984. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1984. DOI: 10.1094/Phyto-74-670.

A carlavirus isolated from Kalanchoe blossfeldiana ' Texas Sunset' and designated KV-2 was compared with a previously characterized carlavirus isolated from cultivar Rotkappchen and designated KV-1. The isolates had similar host ranges, thermal inactivations (~75 C), buoyant densities (1.30 g/cc), and capsid protein molecular masses (33,000- 34,000 daltons). KV-2 was distinguished from KV-1 in that KV-2: systemically infected Chenopodium spp. that were only locally infected by KV-1; had a normal length that was about 30 nm longer than that of KV-1; and was degraded by reagents such as 1% Triton X-100, 5 mM EDTA, and chloroform-carbon tetrachloride that did not degrade KV-1. KV-2 was purified from C. quinoa by clarification of phosphate-buffered crude sap extracts with 1,1,2-trichloro-1,2,2-trifluoroethane (Freon), precipitation with 6% polyethylene glycol, and centrifugation on 10- 40% linear CsCl density gradients. SDS-degraded KV-1 and KV-2 formed lines of partial fusion in Ouchterlony gel double diffusion tests. Isolate-specific antibodies were found in each homologous antiserum in intragel cross-absorption tests. Both isolates reacted in indirect ELISA with antisera to carnation latent, chrysanthemum B, lily symptomless, and potato S viruses, but not to elderberry A, hippeastrum latent, red clover vein mosaic, or narcissus latent viruses. Since only minor differences were found in most of the properties of the two viruses, KV-1 and KV-2 are concluded to be strains of the same carlavirus, here designated kalanchoe latent virus.