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Molecular Plant Pathology

The Biological Properties of a Distinct Tospovirus and Sequence Analysis of Its S RNA. Sheng- Zhi Pang, Department of Plant Pathology, Cornell University, NYSAES, Geneva, NY 14456; Jerry L. Slightom(2), and Dennis Gonsalves(3). (2)Molecular Biology Research, Unit 7242, The Upjohn Company, Kalamazoo, MI 49007; (3)Department of Plant Pathology, Cornell University, NYSAES, Geneva, NY 14456. Phytopathology 83:728-733. Accepted for publication 20 February 1993. Copyright 1993 The American Phytopathological Society. DOI: 10.1094/Phyto-83-728.

A tospovirus isolate from Brazil, designated TSWV-B, was first identified as a unique isolate based on our observation that transgenic plants expressing the N gene of the lettuce strain of tomato spotted wilt virus (TSWV-BL) were susceptible to TSWV-B but showed resistance to both TSWV (L type) and impatiens necrotic spot virus (INSV). TSWV-B was serologically distinct from TSWV and INSV. TSWV-B generally incited symptoms resembling those caused by other TSWV isolates, except TSWV-B systemically infected Petunia hybrida, which is a local-lesion host of TSWV. Unlike the cucurbit isolate TSWV-W, TSWV-B did not infect Cucumis sativus and only occasionally induced systemic infections on C. metuliferus. The complete nucleotide sequence of the S RNA of TSWV-B was determined with cDNA clones to be 3,049 nucleotides long. The genome organization of this S RNA was similar to those of TSWV and INSV. The alignment of the S RNA nucleotide and deduced amino acid sequences with the homologous sequences of TSWV (isolates CNPH1, L3, and BL) and INSV revealed that TSWV-B was related more closely to all the TSWV isolates than to INSV. There was a higher degree of identity among the TSWV isolates than with TSWV-B. Thus, TSWV-B appears to be a distinct tospovirus; however, a precise classification requires additional biological and molecular information on this isolate as well as comparison to other tospovirus isolates.