Two Isometric Viruses in Poinsettias. Renate Koenig, Plant Virologist, Institut für Viruskrankheiten der Pflanzen der Biologischen Bundesanstalt, Messeweg 11, 3300 Braunschweig, Federal Republic of Germany. D.-E. Lesemann, Plant Virologist, Institut für Viruskrankheiten der Pflanzen der Biologischen Bundesanstalt, Messeweg 11, 3300 Braunschweig, Federal Republic of Germany. Plant Dis. 64:782-784. Copyright 1980 American Phytopathological Society. DOI: 10.1094/PD-64-782.

Two isometric viruses were found to be common in commercially grown poinsettias: Fulton’s poinsettia mosaic virus (PoiMV) and a new virus tentatively named poinsettia cryptic virus (PoiCV). We were unable to transmit the two viruses mechanically to common indicator plants, and they did not react with each other’s antisera or antisera to 52 other isometric viruses. PoiMV sedimented as two components with sedimentation velocities (S_rel) of about 53 and 115. After negative staining with uranyl acetate, the two components had average particle diameters of 25 and 31 nm. PoiCV sedimented as one component with S_rel of about 120 and average particle diameter of 28 nm. The two viruses also differed in electrophoretic mobility. PoiMV was detected more reliably in infected plants with enzyme-linked immunosorbent assay or the Derrick method of immunoelectron microscopy than with the agar gel double diffusion test. The latter test usually failed with PoiCV.