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Purification of Maize Dwarf Mosaic Virus by Continuous-Flow Centrifugation. Donald T. Gordon, Associate Professor, Department of Plant Pathology, Ohio Agricultural Research and Development Center, Wooster 44691; Roy E. Gingery, Research Chemist, Agricultural Research Service, U.S. Department of Agriculture, Wooster 44691. Phytopathology 63:1386-1392. Accepted for publication 27 April 1973. DOI: 10.1094/Phyto-63-1386.

Continuous-flow centrifugation with equilibrium-zonal banding was used in the purification of maize dwarf mosaic virus (MDMV). Alterations in conventional techniques of continuous-flow centrifugation were required. The efficiency of the continuous-flow rotor (Beckman B16) was greatest at high flow rates at which only a fraction of the virus sedimented into the gradient during a single passage of extract. Multiple passages through the rotor allowed nearly complete removal (94%) of virus. An average of 89% of virus sedimenting into the rotor was recovered in the virus band from the gradient. Further purification was achieved by isopycnic-zonal centrifugation in CsCl gradients. No detectable impurities were present in final virus preparations as judged by sedimentation properties and serology. Yields of 5-30 µg of purified virus/g of infected corn leaves were obtained. The isopycnic density of MDMV-A depended on the composition of the gradient. In CsCl-water gradients the density was 1.300 g/ml; in CsCl gradients containing 0.5 M potassium phosphate, 1 M urea, pH 7.0, it was 1.285 g/ml. The isopycnic density in sucrose was 1.266 g/ml.