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Factors Affecting Purification of Maize Dwarf Mosaic Virus from Corn. R. K. Jones, Instructor, Department of Plant Pathology and Physiology, Virginia Polytechnic Institute and State University, Blacksburg 24061, Present address of senior author: Plant Pathology Department, North Carolina State University, Raleigh 27607; S. A. Tolin, Assistant Professor, Department of Plant Pathology and Physiology, Virginia Polytechnic Institute and State University, Blacksburg 24061. Phytopathology 62:812-816. Accepted for publication 4 February 1972. DOI: 10.1094/Phyto-62-812.

Maize dwarf mosaic virus (MDMV) was extracted from corn leaves by homogenization in 0.1 M sodium citrate plus 0.5% mercaptoethanol, and was clarified with chloroform and one cycle of differential centrifugation. Pellets were resuspended in 0.005 M sodium citrate, pH 7.0. Purified virus was obtained from sucrose density-gradient columns prepared with the same buffer, and was concentrated by centrifugation. Purified MDMV had an absorption spectrum typical for filamentous viruses containing 5% RNA, showed birefringence, and sedimented at 160-162 S. The concentration of virus after each purification step was measured by analytical density-gradient centrifugation or by serological and infectivity assays. Typical final yields of 9.6-23.6 µg/g fresh wt represented a total recovery of only 25% of the initial virus concentration in the clarified sap. Variations in the purification procedure failed to improve the recovery of virus nucleoprotein. Systemic infectivity assays on corn, analyzed by maximum likelihood and loglog transformation, demonstrated that less than 0.5% of the infectivity of the crude sap was recovered in the purified virus.