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Purification, Electron Microscopy, and Serology of the Dogwood Ringspot Strain of Cherry Leafroll Virus. H. E. Waterworth, Research Plant Pathologist, ARS, USDA, U.S. Plant Introduction Station, Glenn Dale, Maryland 20769; R. H. Lawson, Research Plant Pathologist, Plant Industry Station, Beltsville, Maryland 20705. Phytopathology 63:141-146. Accepted for publication 9 August 1972. DOI: 10.1094/Phyto-63-141.

A virus was mechanically transmitted from petals of two naturally infected Cornus florida trees with chlorotic ringspot leaf symptoms to Chenopodium quinoa and then to plants in 28 of 40 genera. The virus, named dogwood ringspot (DRSV) strain of cherry leafroll virus (CLRV), incited chlorotic ringspot and vein chlorosis in mechanically inoculated dogwood seedlings. We obtained partially purified preparations of the virus by blending fresh tissue in buffer and clarifying the sap with bentonite or chloroform. Resuspended virus pellets of DRSV or CLRV alone always produced two bands 2 mm apart in sucrose gradients centrifuged 2 hr at 98,000 g. Particles of DRSV were consistently smaller than those of CLRV in all buffers tested. Particle diameters varied as much as 2 to 3 nm in populations of particles of each virus, but averaged 24 to 25 nm for DRSV and 28 to 30 nm for CLRV each in Tris [tris (hydroxymethyl) amino methane] buffer. Extracted RNA of DRSV and CLRV was infectious in concentrations as low as 2.5 µg/ml. An immunized rabbit produced antiserum with an antibody titer of 1:512. DRSV is serologically related to CLRV and golden elderberry virus, and distantly related to elm mosaic virus. DRSV and its antiserum have been deposited with the American Type Culture Collection as No. PV 142 and PV-AS-70, respectively.