Morphology of Cauliflower Mosaic Virus

Abstract

In a previous paper (Ann. Phytopath. Soc. Japan 25: 187, 1960), the writer reported a virus obtained from cabbage and rape plants showing mosaic symptom, and identified it as cauliflower mosaic virus (CAMV) described by Tompkins (1937). Electron microscopic examination of partially-purified virus preparations revealed two kinds of spherical particles differing in size, about 10∼13mμ and about 50mμ in diameter, respectively. As the larger particles were thought to be the aggregates of the smaller particles, the virus was reported to be spherical particle of about 10∼13mμ in diameter. In the same year, however, Day and Venables (1960) and Pirone et al. (1960) reported that CAMV was a spherical particle of about 50mμ in diameter. As it seemed likely that the writer's former conclusion was in error, re-examination using more purified preparation was made.Preparation made by the purification method already reported was further purified by sucrose density gradient centrifugation after Day and Venables and Pirone et al. Examination of the tube after density gradient centrifugation showed a distinct opalescent band in the middle and a barely discernible opalescent band near the top. The band at the top contained only smaller particles and was noninfectious. In inoculation tests, the middle band showed high infectivity, and electrom microscopic examination revealed the presence of uniformly-sized spherical particles of approximately 50mμ in diameter. The virus was therefore considered to be the spherical particles of about 50mμ, and the writer corrects his mistake in identification of the virus particles reported in his previous paper.