VIEW ARTICLE

Cytology and Histology

Ultrastructural Cytology of Soybean Infected with Mild and Severe Strains of Soybean Mosaic Virus. P. L. Hunst, Graduate assistant, Department of Plant Pathology and Physiology, Virginia Polytechnic Institute and State University (VPI & SU), Blacksburg 24061; S. A. Tolin, associate professor, Department of Plant Pathology and Physiology, Virginia Polytechnic Institute and State University (VPI & SU), Blacksburg 24061. Phytopathology 73:615-619. Accepted for publication 17 November 1982. Copyright 1983 The American Phytopathological Society. DOI: 10.1094/Phyto-73-615.

Two soybean mosaic virus (SMV) strains from Virginia, VA/G1 and OCM/G3, and two SMV strains from Illinois, IL/G1 and IL/G3, were compared biologically and ultrastructurally in soybean (Glycine max ‘Essex’). Strain VA/G1 induced severe mosaic symptoms on soybean and abundant pinwheel inclusions in the cytoplasm of infected cells. Strains OCM/G3, IL/G3, and IL/G1 induced extremely mild symptoms with both pinwheels and cytoplasmic strands. Cytoplasmic strands contained virus particles and traversed the vacuole of infected cells. The four strains were closely related in serological tests. In a time-sequence study, pinwheels were detected in leaves infected with all of the strains 9 days after inoculation. Cytoplasmic strands were first observed at 10 days in cells infected with strain OCM/G3 or IL/G3 and at 11 days with IL/G1. No cytoplasmic strands were observed in cells infected with the severe strain, VA/G1. Production of cytoplasmic strands was concluded to be an intracellular virus localization mechanism leading to the tolerant reaction of Essex soybean to the three mild strains of SMV.