Blueberry scorch disease, caused by the carlavirus Blueberry scorch virus(BlScV), is a serious disease of highbush blueberry (Vaccinium corymbosum L.) in North America and Europe. Symptoms of BlScV infection in highbush blueberry include necrosis of flower blossoms and young leaves, shoot blight, and chlorosis. In June 2003, BlScV was detected for the first time in cranberry (Vaccinium macrocarpon L.) in Abbotsford, British Columbia, Canada using double antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA). Ten uprights were sampled from different locations in the bog, seven of which tested positive using DAS-ELISA. To confirm infection, total nucleic acid was extracted from infected cranberry leaf tissue according to an established protocol (2). Primers were developed against the published NJ-2 sequence of BlScV (GenBank Accession No. NC_003499). The forward primer, BS4586F (5′-CTTCAGGATGAGTGGTGCAA-3′), and the reverse primer, BS5164R (5′-CGCGTGCTGGAAGCATACAA-3′), were used in reverse-transcription polymerase chain reaction (RT-PCR) to amplify a portion of the RNA-dependent RNA polymerase gene of BlScV. The amplicons of the expected size were sequenced and the nucleotide sequence of the product showed 82% homology, and the predicted amino acid sequence had 91% homology with the published NJ-2 sequence. A random survey for BlScV in cranberry bogs in the Pacific Northwest Region of North America was conducted. Testing revealed the presence of BlScV in 7 of 42 bogs in British Columbia, Canada, 2 of 12 bogs in Oregon, and 3 of 18 bogs in Washington. Nucleotide sequencing of RT-PCR products of BlScV from a Washington bog showed 87 and 96% homology at the nucleotide and predicted amino acid level, respectively, in the methyltransferase of the NJ-2 strain using forward primer, BS276F (5′-CCGTCTGCAAGACATTAGAG-3′), and reverse primer, BS743R (5′-TCTTCTTCACCTCGTACTCG-3′). Several bogs had a high incidence of BlScV infection, with over 70% of the sampled uprights testing positive. Some infected cranberry bogs were adjacent to infected blueberry fields, while others were isolated. Transmission of the virus is likely to have occurred by aphids, which are known to be vectors of BlScV (1). Presently, BlScV appears to be asymptomatic in cranberry. To our knowledge, this is the first report of BlScV infecting cranberry. The potential for infection of other Vaccinium spp., such as lowbush blueberry (V. angustifolium Aiton), rabbiteye blueberry (V. ashei Reade), native Pacific Northwest species (V. membranaceum Douglas ex Torrey, V. ovatum Pursh, and V. parvifolium Smith), and ornamental Vaccinium spp. needs to be investigated.
References: (1) P. R. Bristow et al. Phytopathology 90:474, 2000. (2) D. W. Hughes and G. Galau. Plant Mol. Biol. Rep. 6:253, 1988.