Genetic and biological characterisation of a Grapevine virus A isolate from the Czech Republic

An isolate of <i>Grapevine virus A</i> (GVA) from the Czech Republic was obtained from the grapevine cultivar Müller Thurgau. Symptoms of GVA – Kober stem grooving disease were not observed in the infected grapevines (which had been grafted onto Kober 5BB rootstock). A partial genomic sequence of the GVA isolate, 1523 nucleotides long, was obtained. The sequence completely covers the genes for both a movement and a coat protein. Compared to the GVA sequences available in databases, the nucleotide identity reached 84%. The amino acid identity in the movement protein reached 88%, and 98% in the coat protein.

Detecção do Grapevine virus A e Grapevine virus B por hibridização "dot-blot" com sondas moleculares não radioativas

O vírus A da videira (Grapevine virus A, GVA) e o vírus B da videira (Grapevirus virus B, GVB) estão associados à acanaladura do lenho de Kober ("Kober stem grooving") e ao fendilhamento cortical da videira ("grapevine corky bark"), respectivamente. Este trabalho descreve o uso de sondas moleculares de cDNA na detecção de isolados do GVA (GVA-SP) e do GVB (GVB-C-SP e GVB-I-SP) em videiras (Vitis spp.) e fumo (Nicotiana occidentalis). As sondas marcadas com digoxigenina foram produzidas por RT-PCR utilizando oligonucleotídeos específicos para os genes da proteína capsidial. Os RNA totais foram extraídos de 45 plantas de diversas variedades de videira e de 13 plantas de fumo inoculadas mecanicamente com o GVB. Os RNA extraídos das plantas infetadas, indexadas biologicamente, hibridizaram com as sondas, não se verificando reação com plantas sadias. Para confirmar os resultados de hibridização, foram também feitos testes de RT-PCR. A utilização de hibridização "dot-blot" com sondas de cDNA mostrou-se eficaz na detecção dos vírus com especificidade e sensibilidade, ressaltando-se que, preferencialmente, folhas maduras e ramos dormentes devem ser utilizados nos testes diagnósticos para o GVB e GVA, respectivamente.

Characterization of Grapevine Rugose Wood Disease Sources from Italy

A collection of 27 sources of grapevine rugose wood (RW) disease from a viticultural region in northern Italy was analyzed by graft-inoculating vines of three selective Vitis indicators (V. rupestris cv. St. George, V. berlandieri × V. riparia cv. Kober 5BB, and hybrid cv. LN 33). On the basis of stem reactivity, different groups were identified among the selected RW inoculum sources: nine isolates induced pitting only on cv. St. George, whereas four induced grooving only on cv. Kober 5BB. These two groups were classified as isolates of rupestris stem pitting and Kober stem grooving. Three of the remaining isolates induced wood abnormalities on cvs. LN 33 and Kober 5BB, seven induced wood abnormalities on cvs. St. George and Kober 5BB, and four induced symptoms on all three indicators. These groups may represent RW sources with various disease combinations. RW-affected grapevine clones used as inoculum sources also were tested for virus infections by enzyme-linked immunosorbent assay (ELISA). ELISA revealed the presence of grapevine fleck virus, grapevine leafroll-associated closterovirus 1 and 3, and grapevine trichovirus A. These viruses infected most of the selected RW sources. However, eight of the latter were ELISA-negative. The findings are discussed, and the biological and etiological complexity of the RW phenomena in grapevine is confirmed.

First Report of Grapevine Kober Stem Grooving in the United States

The last decade has brought extensive new plantings of grapevines (Vitis vinifera L.) to California vineyards. In some vineyards, severe viruslike problems have been observed (2). To ascertain possible causal agent(s), extensive testing for grapevine viruses was initiated. Testing included a 2-year woody index on indicators V. rupestris cv. Saint George, LN 33, V. vinifera cv. Cabernet Franc, and Kober 5BB. To our knowledge, this is the first field survey for grape virus diseases in the United States that includes woody indexing on Kober 5BB, a relatively new indicator for the grapevine rugose wood diseases (1). A Sonoma County field selection of Sauvignon Blanc grafted to the rootstock Freedom was included in these tests; the 2-year-old vines exhibited stunting, leaf rolling, leaf yellowing, wood necrosis, and pitting symptoms at the graft union. When indexed on the four indicators, the following disease symptoms were observed: stem pitting on V. rupestris; corky bark on LN 33; leafroll on Cabernet Franc; and stem grooving on Kober 5BB. An enzyme-linked immunosorbent assay confirmed the presence of grapevine leafroll-associated viruses 2, and 3, as well as Grapevine Virus A, which is associated with Kober stem grooving. The Sauvignon Blanc selection appears to be infected with several grapevine viruses, as is often the case when virus symptoms in vineyards are severe. Among these disease agents, only Kober stem grooving is reported to cause the severe pitting and grooving symptoms observed on the indicator Kober 5BB (1). This is the first report of Kober stem grooving in the United States. References: (1) R. Garau et al. Vitis 33:161, 1994. (2) D. A. Golino. Am. J. Enol. Vitic. 44:148, 1993.