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Discrepancies in the Intracellular Behavior of Three Strains of Tobacco Mosaic Virus, Two of which are Serologically Indistinguishable. A. L. Granett, Department of Plant Pathology, University of California, Davis 95616, Present address of senior author: Department of Plant Pathology, New York State Agricultural Experiment Station, Cornell University, Geneva, New York 14456; T. A. Shalla, Department of Plant Pathology, University of California, Davis 95616. Phytopathology 60:419-425. Accepted for publication 1 October 1969. DOI: 10.1094/Phyto-60-419.

Attempts were made to distinguish two common strains of tobacco mosaic virus, U-1 (D) and U-1 (SB), and the U-5 strain by symptomatology, serology, and light and electron microscopy. In cells of Turkish tobacco (Nicotiana tabacum), the size, shape, and fine structure of the intracellular virus crystals formed by both U-1 (D) and U-1 (SB) were identical, but they were distinct from those formed by U-5. Also, the two common strains were indistinguishable from each other and different from U-5 on the basis of symptoms in various plants and in serological tests. The common strains appeared distinguishable only in differing tendencies to produce amorphous inclusions (X-bodies) and in the frequency with which the virus occurred in chloroplasts. The U-1(SB) strain was more effective than U-1(D) or U-5 in causing the formation of X-bodies. The chloroplasts frequently contained virions of either U-1(SB) or U-5, but only rarely U-1(D).