Disease Note.

The Occurrence of Tomato Ringspot Virus in Ponthieva racemosa . J. M. Yao, Department of Plant Pathology, North Carolina Slate University, Raleigh 27695. F. H. Tainter, Department of Forest Resources, and M. T. Zimmerman, Plant Pathology and Physiology, Clemson University, Clemson, SC 29634 and O. W. Barnett, Department of Plant Pathology, North Carolina Slate University, Raleigh 27695. Plant Dis. 78:925. Accepted for publication 27 May 1994. Copyright 1994 The American Phytopathological Society. DOI: 10.1094/PD-78-0925E.

A tomato ringspot virus (ToRSV) was isolated from a terrestrial orchid plant, Ponthieva racemosa (Walter) Mohr, collected in the Guajataca Forest Reserve in Puerto Rico. Its host range was like that of the Cymbidium isolate (1). Sap extracted from infected P. racemosa leaves and purified virus reacted strongly with ToRSV antiserum in repeated double antibody sandwich enzyme-linked immunosorbent assays (DAS-ELISAs) (healthy P. racemosa as control). No reaction was observed between this orchid isolate and antisera to 10 other viruses, including tobacco ringspot. The virus particles sedimented as three components in glycerol gradients. A mechanically inoculated mixture of bottom and middle components caused shoot necrosis after 7 days and plant death after 20 days in P. racemosa, and severe necrotic local lesions and apical necrosis on Chenopodium quinoa. One polypeptide with a molecular weight of 59,000 ± 500 Da was associated with the virus. Virus particles were isometric and 27.2 nm in diameter. This is the first report of ToRSV in P. racemosa and only the second report in orchids.