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Purification, Partial Characterization, and Serological Comparison of Soybean Mosaic Virus and its Coat Protein. M. M. Soong, Contribution from the Plant Pathology Department and Agriculture Experiment Station, College of Agriculture, University of Illinois, Urbana, 61801; G. M. Milbrath, Contribution from the Plant Pathology Department and Agriculture Experiment Station, College of Agriculture, University of Illinois, Urbana, 61801, Current address of junior author: State Department of Agriculture, Salem, OR 97302. Phytopathology 70:388-391. Accepted for publication 16 October 1979. Copyright 1980 The American Phytopathological Society. DOI: 10.1094/Phyto-70-388.

An Illinois isolate of soybean mosaic virus (SMV-IL) was purified from cultivar Kanrich soybean leaves, 1618 days after inoculation by chloroform-butanol clarification, followed by polyethylene glycol (PEG) precipitation and ultracentrifugation, first through a 30% sucrose solution and then to density equilibrium in cesium chloride. The purified virus absorbed maximally between 258263 nm and minimally at 244 nm. The ratio of absorption at 260 and 280 nm (A260/A280) of purified virus (not corrected for light scattering) was 0.79. Viewed in the electron microscope, SMV appeared to be homogeneous, unaggregated, and to have a most frequent length of 675750 nm. Infectious SMV RNA was separated from protein by disruption of virus in 2 M lithium chloride (LiCl). Purified SMV protein migrated as a single band in SDS-polyacrylamide gels (SDS-PAGE) with a molecular weight of 32,150 420 for SMV-IL and 33,075 1,889 for PV-94-ATCC. The antigenic specificity of protein from degraded SMV was not identical to that of intact virus particles. The SMV is identical to SMV-PV-94-ATCC based on serological titer, cross-absorption studies, coat protein molecular weight estimation on SDS-PAGE, and ultraviolet absorption spectra.