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Etiology

Evidence for a Latent Viruslike Agent in Cassava. C. J. Gabriel, Research plant pathologist, U. S. Plant Introduction Station, Glenn Dale, MD 20769; R. Walsh(2), and B. L. Nolt(3). (2)Plant pathologist, U. S. Plant Introduction Station, Glenn Dale, MD 20769; (3)Cassava virologist, Centro Internacional de Agricultura Tropical (CIAT), Apartado Aereo 6713, Cali, Colombia. Phytopathology 77:92-95. Accepted for publication 19 June 1986. 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, 1987.. DOI: 10.1094/Phyto-77-92.

Several species of double-stranded RNA (dsRNA) were found to occur in the cassava (Manihot esculenta) clone Secundina, which was thought to be virus-free. A large dsRNA molecule (6.6 106 Mr = relative molecular mass)(L-dsRNA) was shown to be graft, but not mechanically transmitted and occurred primarily in a nuclear-rich fraction isolated from dsRNA containing Secundina plants. Viruslike particles were not detected in plants containing the L-dsRNA using a variety of purification procedures. L-dsRNA was also found in two non-Secundina M. esculenta introductions. Smaller dsRNAs (S-dsRNAs), ranging mainly between 0.61 and 0.41 106 Mr, were also detected in some Secundina plants containing the L-dsRNA. The S-dsRNAs were not transmissible by mechanical inoculation or grafting. All dsRNAs could be eliminated by meristem-tip culture of infected plants. DsRNA analysis is recommended for indexing cassava for this latent viruslike agent.