VIEW ARTICLE

Etiology

A Carlavirus from Kalanchoë blossfeldiana. S. S. Hearon, Research plant pathologist, Agricultural Research Service, U.S. Department of Agriculture, Beltsville, MD 20705; Phytopathology 72:838-844. Accepted for publication 8 December 1981. 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, 1982.. DOI: 10.1094/Phyto-72-838.

A virus with slightly flexuous, filamentous particles was isolated from a symptomless Kalanchoë blossfeldiana ‘Rotkappchen’ plant. The virus, designated kalanchoë virus-I (KV-I), had a thermal inactivation point between 65 and 70 C, was inactivated by aging in vitro at ambient room temperature for 3–5 days, and had particles with a normal length of 600–620 nm in PTA. The experimental host range was limited to kalanchoë, several Chenopodium spp. and Tetragonia expansa. Chenopodium quinoa, grown at 20–28 C under 19,368–21,520 lux (1,800–2,000 ft-c) of supplemental fluorescent light for 16 hr/day during periods of low natural light intensities, was used for virus bioassay and propagation. The virus was purified by trituration of leaves in 0.1 M K₂HPO₄, containing 0.1% 2-mercaptoethanol, 5 mM EDTA, and 1% Triton X-100; clarification of the sap with chloroform and carbon tetrachloride; and precipitation of the virus with 4% polyethylene glycol-6000. Further purification was attempted by passage of partially purified virus preparations through a column of controlled-pore glass beads or density gradient centrifugation. The buoyant density of KV-I in cesium chloride was 1.311 g/cm³, the sedimentation coefficient was ~ 170 S, and the apparent molecular weight of the coat protein was 34,000–36,000 daltons. KV-I is distantly related to carnation latent, chrysanthemum B, lily symptomless, and potato S viruses, and is unrelated to elderberry A, hippeastrum latent, narcissus latent, potato M, or red clover vein mosaic viruses in micropreciptin tests and serologically specific electron microscopy. The properties of KV-I are typical of a carlavirus, but distinct from previously characterized members of this virus group.