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Disease Note.

Occurrence of Tobravirus Infections in Peperomia, Hosta, and Phlox in the Midwestern U.S. B. E. Lockhart, Department of Plant Pathology, University of Minnesota, St. Paul 55108 Gaia Morelli, St. Paul Academy, St. Paul, MN 55105 . J. Westendorp, Walters Gardens, Inc., Zeeland, MI 49464. Plant Dis. 79:1249. Accepted for publication 16 October 1995. Copyright 1995 The American Phytopathological Society. DOI: 10.1094/PD-79-1249D.

Tobraviruses were detected in three perennial ornamentals, Peperomia, Hosta, and Phlox in the midwestern U.S. states of Minnesota, Michigan, and Illinois. Tobravirus infection was associated with vein-clearing in Peperomia caperata Yunck. in commercial greenhouses in Minnesota, with marginal leaf necrosis in Hosta spp. in Minnesota and Illinois, and with foliar mosaic of Phlox divaricata L. in Michigan. Virus particles negatively stained with sodium phosphotungstate (PTA, pH 6.8) were 22 nm wide in all three cases. The viruses in Peperomia, Hosta, and Phlox had modal particle lengths of 90 and 180 nm, 85, 115, and 230 nm, and 45, 70, 150, and 230 nm, respectively. All three virus isolates reacted positively in immunosorbent electron microscopic tests with antisera to tobacco rattle (TRV, American Type Culture Collection PVAS 75) and pea early-browning (Moroccan isolate) (1) tobraviruses. None of the virus isolates infected Dwarf Gray Sugar pea systemically. The tobraviruses from Peperomia and Phlox readily infected Chenopodium quinoa Willd., Nicotiana clevelandii Gray, and N. benthamiana Domin., producing symptoms typical of TRV, but the Hosta tobraviruses were not transmitted by mechanical inoculation to any of these host plants. Tobraviruses occur commonly in Europe, but in North America TRV has previously been reported to occur only in California and Oregon. The occurrence of tobraviruses in ornamental species that move freely in international commerce suggests a need for more stringent monitoring of virus infection in these crops.

Reference: (1) B. E. L. Lockhart and H. U. Fischer. Phytopathology 66:1391, 1976.