Problems with Interpretation of Serological Assays in a Virus Survey of Orchid Species from Puerto Rico, Ecuador, and >Florida. M. S. Elliott, Senior Biological Scientist, Plant Pathology Department, University of Florida, P.O. Box 110680, Gainesville 32611. F. W. Zettler, Professor, Plant Pathology Department, University of Florida, P.O. Box 110680, Gainesville 32611; M. T. Zimmerman, Agricultural Scientist, Plant Pathology and Physiology Department, Clemson University, Clemson, SC 29634-0377; O. W. Barnett, Jr., Professor and Chairman, Plant Pathology Department, North Carolina State University, Raleigh 27695-7616; M. D. LeGrande, Technical Assistant, Plant Pathology Department, University of Florida, P.O. Box 110680, Gainesville 32611. Plant Dis. 80:1160-1164. Accepted for publication 2 July 1996. Copyright 1996 The American Phytopathological Society. DOI: 10.1094/PD-80-1160.

Leaf samples collected in May 1990 from wild and cultivated orchids in Puerto Rico were tested for odontoglossum ringspot virus (ORSV), cymbidium mosaic virus (CymMV), tobacco mosaic virus common strain, tobacco mild green mosaic virus, two strains of cucumber mosaic virus, and cymbidium ringspot virus (CymRSV) with sodium dodecyl sulfate immunodiffusion. enzyme-linked immunosorbent assay (ELISA), and/or Western blot (immunoblot) procedures. Leaf tissue from orchids cultivated in Gainesville, FL, and from the wild in Ecuador were similarly tested. No virus was detected in the 277 wild orchids, and only ORSV, CymMV, or both ORSV and CymMV were detected in 20, 73, and 22 cultivated orchids, respectively, from Puerto Rico and Florida. Several orchid plants gave ELISA reactions greater than three times the negative control with all the virus antisera tested. Other methods did not confirm the presence of virus in these plants, however. Indeed, several preimmune sera also reacted with some of these plants. Caution must be used in interpretation of low ELISA values even when these reactions are clearly greater than those of uninfected controls. These results illustrate the need to utilize more than one diagnostic technique before discarding a valuable orchid plant.

Keyword(s): tomato ringspot virus