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  • Author or Editor: Mark M. Bray x
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In 2004, two surveys were conducted to assess the presence of four viruses in marketable blackberry nursery stock. The U.S. survey consisted of dormant nursery stock received from 11 nurseries in the southern, southeastern, midwestern, northeastern, and Pacific northwestern regions of the U.S. The second survey was focused only on Arkansas licensed propagating nurseries with samples collected during the growing season. Samples were tested using reverse transcription–polymerase chain reaction or enzyme-linked immunosorbent assay for the presence of Blackberry yellow vein associated virus (BYVaV), Raspberry bushy dwarf virus (RBDV), Tomato ringspot virus (ToRSV), and Tobacco ringspot virus (TRSV). Of the total samples in the U.S. survey, there were 9% that tested positive for virus infection. Ninety percent of the positives were infected with BYVaV. Forty percent of these were detected in `Triple Crown', 40% in `Chickasaw', and 20% in `Apache'. The remaining 9% of the total positive virus samples were infected with TRSV and 100% of these were in `Triple Crown'. No viruses were found on any samples of `Chester Thornless'. In the Arkansas survey, 11% of the total samples tested positive for virus. Of these, 50% were infected with BYVaV.

The percent infected with BYVaV was distributed evenly among `Apache', `Chickasaw', and `Kiowa'. The other 50% of the infected samples were positive for TRSV (67% `Apache', 33% `Chickasaw'). There was one mixed infection of BYVaV and TRSV detected in `Apache'. These findings indicate that BYVaV is the most prevalent virus found in nursery stock and that the occurrence of BYVaV is not restricted to a single region or cultivar.

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Latent infection of Blackberry yellow-vein associated virus (BYVaV) in `Chickasaw' blackberry has been reported. However, plants with characteristic leaf symptoms, such as vein yellowing, chlorotic mottling, and oak-leaf patterns, have tested positive for BYVaV using reverse-transcription polymerase chain reaction. Experiments were initiated to determine if the symptoms expressed in BYVaV infected `Chickasaw' were caused by mixed virus infections. BYVaV, a recently identified crinivirus, was evaluated for synergistic interactions with Tobacco ringspot virus (TRSV), Tomato ringspot virus (ToRSV), and Raspberry bushy dwarf virus (RBDV). `Chickasaw' blackberry plants infected with BYVaV (single infection) were used as receptor plants to establish mixed virus infections with TRSV and ToRSV transmitted by nematodes and RBDV transmitted by bottle grafts. Characteristic symptoms of multi-virus infection will be presented and discussed.

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