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Etiology

Association of Tomato Ringspot Virus with a Chlorotic Leaf Streak of Cymbidium Orchids. L. M. Goff, Graduate Assistant, Botany Department, University of Maryland, College Park, MD 20742; M. K. Corbett, Professor, Botany Department, University of Maryland, College Park, MD 20742. Phytopathology 67:1096-1100. Accepted for publication 28 February 1977. Copyright © 1977 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-67-1096.

An isolate of tomato ringspot virus was obtained from plants of Cymbidium Snowbird ‘Jayhurst’ that exhibited faint chlorotic leaf streaks. The virus infected a wide range of herbaceous plants and induced symptoms characteristic of viruses of the ringspot group. In crude sap the dilution end point of the virus was between 1:100 and 1:1,000, thermal inactivation was 50-60 C for 10 min, and infectivity persisted for 48 hr at 25 C. Electron microscopy of shadowed leaf-dip preparations and negatively stained purified virus preparations revealed the presence of isometric particles having a diameter of 28 nm. Two light-scattering zones, with estimated sedimentation coefficients of 120 S and 126 S, were obtained after sucrose density-gradient centrifugation of partially purified virus preparations. Infectivity was associated with the light-scattering zones. A third, noninfectious zone, with an estimated sedimentation coefficient of 57 S, was observed in some preparations. Gel double-diffusion serological tests showed that the isolate reacted with antisera to strains of tomato ringspot virus, but not with antisera to tobacco ringspot virus, cucumber mosaic virus, cymbidium ringspot virus, or cherry leaf roll virus.