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Identification of Sugarcane Striate Mosaic-Associated Virus by Partial Characterization of Its Double-Stranded RNA

First author: Department of Plant Pathology, University of California, Riverside 92521-0122; second author: Bureau of Sugar Experiment Stations, Old Cove Road, Woodford, Queensland 4514, Australia; and third author: Department of Applied and Molecular Ecology, University of Adelaide, Waite Campus, Glen Osmond, SA 5064, Australia

Sugarcane striate mosaic (ScSM)-affected sugarcane leaves contain a disease-associated 9-kilobase (kb) double-stranded RNA (dsRNA), usually together with 6- and 2.6-kb dsRNAs. The purified 9-kb dsRNA was amplified by the randomly primed polymerase chain reaction (PCR) and cloned. The nucleotide sequences of three separate regions, representing about 2.55 kb (28%) of the dsRNA sequence, were found to have significant similarities to viruses in the genera Capillo-, Carla-, Fovea-, Potex-, Poty-, Tricho-, and Tymovirus. Greatest overall similarity was found to apple stem pitting virus, with less similarity to blueberry scorch virus and potato virus M. A standard virus purification procedure was used to identify slightly flexuous filamentous particles that copurified with the disease-associated RNA. Particle modal lengths were approximately 950 and 1,900 nm with a diameter of 15 nm. Preparations contained a 51-kDa putative capsid protein and a 9-kb single-stranded RNA with a probable 3′ polyadenylate tract. These ScSM-associated virus particles differ physically from viruses in existing genera because of their relative rigidity, length, and putative coat protein size. Reverse-transcription PCR with a primer pair designed from the sequenced segments amplified a 820-base pair fragment from ScSM-affected but not healthy sugarcane plants.

Additional keywords: AMV, CF11, CMV, microgranular cellulose, phytoplasma, PSbMV, TMV.