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Improved Purification of Two Potato Carlaviruses. S. M. Tavantzis, Assistant professor, Department of Botany and Plant Pathology, University of Maine, Orono 04469; Phytopathology 73:190-194. Accepted for publication 22 July 1982. Copyright 1983 The American Phytopathological Society. DOI: 10.1094/Phyto-73-190.

Electron microscopic examinations of potato virus M (PVM), and potato virus S (PVS), purified by procedures employing clarification with organic solvents, revealed that virus preparations were unsuitable for characterization studies because of extensive fragmentation of the particles. Considerably higher virus yields and percentages of intact particles were obtained by a new purification scheme that entailed sap clarification with calcium phosphate, polyethylene glycol precipitation, two cycles of differential centrifugation using sucrose cushions, rate zonal centrifugation in sucrose, and equilibrium centrifugation in Cs2SO4. The estimated yield of PVM, obtained from equilibrium density gradient zones, was 46 ± 9 μg of virus per gram of tissue, whereas that of PVS was 31 ± 6 μg of virus per gram of tissue. Purified PVM or PVS behaved as homogeneous systems in sedimentation-velocity experiments.