Symptoms that resembled virus infection were observed on several smooth blackberry (Rubus canadensis L.) plants in the Great Smoky Mountain National Park (GSMNP) during a project carried out in the summer and fall of 2006 as part of All Taxa Biodiversity Inventory (ATBI) activities (2). Diseased specimens showed chlorosis and mottling as well as deformation of younger leaves. Symptomatic leaves were collected, and preliminary screening by double-antibody sandwich (DAS)-ELISA did not detect Tobacco ringspot virus (TRSV), Tomato ringspot virus (ToRSV), Tomato spotted wilt virus (TSWV), Raspberry bushy dwarf virus (RBDV), or Impatiens necrotic spot virus (INSV) in these samples. Double-stranded RNA (dsRNA) extracted from symptomatic leaves of two diseased specimens (GSM-1 and GSM-2) revealed two bands with sizes estimated at 7.5 and 6.5 kb. Purified dsRNAs from specimen GSM-1 were used as a template to generate random-primed cDNA clones. Several clones were sequenced and analysis of approximately 3 kb of contiguous sequence (GenBank Accession No. EU419645) revealed the presence of a single open reading frame encoding a protein containing the complete proteinase and partial polymerase domains. BLAST analysis showed that the virus from R. canadensis shared 77 and 87% nucleotide and amino acid sequence identity, respectively, with the recently described putative sadwavirus Black raspberry necrosis virus (BRNV) (GenBank Accession No. NC_008182) (1), suggesting that this virus is a distinct isolate of BRNV. The virus shared a lower degree of identity with the analogous sequences of other viruses belonging to the genus Sadwavirus, with only 48 and 37% identity with Strawberry mottle virus (GenBank Accession No. NC_003445) and Satsuma dwarf virus (GenBank Accession No. NC_003785), respectively. To our knowledge, this is the first report of BRNV in GSMNP and Tennessee, indicating that it may be widespread in native Rubus spp. through the southeastern United States.
References: (1) A. Halgren et al. Phytopathology 97:44, 2007. (2) M. J. Sharkey. Fla. Entomol. 84:556, 2001.
