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Etiology

An Antigenically Distinct Strain of Cassava Common Mosaic Virus Infecting Cnidoscolus aconitifolius. F. W. Zettler, Professor, Department of Plant Pathology, University of Florida, Gainesville 32611; M. S. Elliott, biological scientist I, Department of Plant Pathology, University of Florida, Gainesville 32611. Phytopathology 76:632-638. Accepted for publication 12 August 1985. Copyright 1986 The American Phytopathological Society. DOI: 10.1094/Phyto-76-632.

A strain of cassava common mosaic virus (CCMV-Ch) was detected in plants of chaya (Cnidoscolus aconitifolius) grown in Florida. The virus induced systemic mosaic symptoms in manually inoculated plants of chaya, cassava (Manihot esculenta), Ricinus communis, Euphorbia spp., Jatropha spp., and Nicotiana benthamiana. Local lesions were induced in Cassia occidentalis, Chenopodium amaranticolor, Chenopodium quinoa, Datura stramonium, and Gomphrena globosa. Of 140 flexuous rod-shaped virus particles measured in negatively stained leaf extracts of Nicotiana benthamiana, 77% were 473-543 nm long, with a main maximum at 520 nm. Cytoplasmic inclusions seen by light and electron microscopy in infected leaves of chaya and Nicotiana benthamiana were similar to those previously described for cassava common mosaic and other potexviruses. Up to 1.67 mg of purified CCMV-Ch per gram of infected leaf tissue of Nicotiana benthamiana was obtained by clarification in n-butanol and chloroform, two precipitations with 8% (final concentration) polyethylene glycol 6,000, and differential centrifugation. Maximum CCMV-Ch antigen titers of 1/256, 1/16, and 1/8 occurred in leaf extracts of Nicotiana benthamiana, cassava, and chaya, respectively, when subjected to double diffusion tests (0.8% Noble agar, 0.5% sodium dodecyl sulfate, 1.0% NaN₃). Reciprocal sodium dodecyl sulfate immunodiffusion and unilateral double antibody sandwich enzyme-linked immunosorbent assay tests showed that CCMV-Ch is serologically related to, but distinct from, nine cassava isolates of CCMV from Brazil, Colombia, and Taiwan. CCMV-Ch could not be serologically distinguished from a chaya CCMV isolate from Yucatan, Mexico.