Transmissão experimental do Grapevine virus B pela cochonilha Pseudococcus longispinus Targioni-Tozzetti (Hemiptera: Pseudococcidae) Transmission of the Grapevine virus B by the mealybug Pseudococcus longispinus Targioni-Tozzetti (Hemiptera:Pseudococcidae) in Brazil

Em São Paulo, existem dois isolados do Grapevine virus B (GVB), sorologicamente semelhantes e sintomatologicamente distintos, que causam a doença denominada fendilhamento cortical ("grapevine corky bark", GCB). Na literatura estrangeira existem relatos de que o GVB pode ser transmitido por cochonilhas brancas. O objetivo do presente trabalho foi o de verificar a transmissibilidade do GVB de videira infectada para videira sadia através da cochonilha da espécie Pseudococcus longispinus. Os dois isolados do vírus foram testados: o isolado comum (GVB-C) e o isolado Itália (GVB-I). A confirmação de infecção foi feita através da análise visual de sintomas, ELISA e RT-PCR. Em todos os testes de inoculação experimental, os primeiros sintomas da virose foram notados com, aproximadamente, 8 a 12 meses após a exposição às cochonilhas. Plantas sadias da variedade LN-33, mantidas ao redor de uma planta infectada com o GVB-C e altamente infestada pela P. longispinus, tornaram-se infectadas com incidência de 54,2%, após 4 anos. Empregando-se inoculação experimental com cochonilhas virulíferas, plantas da indicadora LN-33 apresentaram infecção de 46,2% e 40,0% para o GVB-C e GVB-I, respectivamente, após 3 anos de observações. Apesar desta espéciede cochonilhaocorrer de maneira eventual nos vinhedos do Estado de São Paulo, precauções devem ser tomadas em áreas onde são mantidos clones sadios de variedades de copa e de porta-enxerto de videira, visto que esses insetos, além de possuírem grande número de plantas hospedeiras, também podem transmitir outros importantes vírus da videira.<br>In the State of São Paulo, Brazil, there are two isolates of Grapevine virus B (GVB) associated with grapevine corky bark disease (GCB). Although serologically similar, they induce distinct reaction on some grape varieties. They are called GVB-C for common isolate and GVB-I for isolate obtained from the variety Italia. The objective of this work was to verify the transmission of both GVB isolates from infected to healthy plants by the mealybug Pseudococcus longispinus. The transmission of the virus was determined by visual analysis of symptoms, ELISA and RT-PCR. In all transmission experiments, grape indicator plants that had been exposed to presumably viruliferous mealybugs reacted in 8-12 months with a typical symptoms of GCB. Healthy LN-33 plants, maintained around one GCB-C affected LN-33 plant, highly infested by the mealybug, became infected with incidence of 54.2% after four years. Experimental inoculation of healthy LN-33 plants with viruliferous mealybugs resulted in infection rates of 46.2% for GVB-C and 40.0% for GVB-I, after three years. Although P. longispinus occurs eventually in São Paulo State vineyards, preventive control measures for this insect must be taken on areas where healthy clones of scion and rootstock varieties are maintained

Distribution of Rupestris stem-pitting-associated virus variants in two Australian vineyards showing different symptoms

The incidence of Rupestris stem-pitting-associated virus (RSPaV) in two vineyards in South Australia was studied by comparing symptoms with the results obtained from biological indexing and from virus detection by reverse-transcription-polymerase chain reaction (RT-PCR). Vineyard 1 was an experimental block comprising a number of varieties grafted onto Vitis rupestris cv. St George rootstocks for the detection of Rupestris stem pitting disease. No swelling at graft union or decline was observed at 3 years, but some vines showed pitting on the rootstock trunk. Vineyard 2 contained Vitis vinifera cv. Shiraz (Syn. Syrah) vines on Paulsen 1103 rootstock, showing a range of symptoms including swelling of the graft union, pitting on the rootstock, leaf reddening and vine decline, resembling those in Syrah Decline, a disorder known to occur in this variety. RT-PCR using the coat-protein-specific primers detected RSPaV in all samples from either vineyard including symptomless V. rupestris cv. St George, which is used as the biological indicator for the virus. In contrast, a pair of primers designed from the replicase gene detected the virus only in symptomatic vines, whereas the symptomless St George control and nonsymptomatic vines in both vineyards tested negative. An assay for 12 other major grapevine viruses showed that none were associated with either type of symptom. Comparison of a 628-bp amplicon on the replicase gene in 13 RSPaV isolates showed that while they had 96–99% nucleotide sequence identity to each other, their identity to the American isolates from California and New York was around 65%. This low homology may indicate that a different virus species is present. The variability was more pronounced between the two vineyards than among the virus isolates in the Shiraz vines within the same vineyard. However, even the vines of the same vineyard did not contain viruses with exactly the same sequence homology. We found no association between the type of symptom expressed and the sequence variation in the amplicons in either vineyard. The sequence variants in Vineyard 1 showed a closer cluster than in Vineyard 2

Efeito da Xylella fastidiosa em cafeeiros em diferentes regiões edafoclimáticas Effect of Xylella fastidiosa in coffee plants at different edaphoclimatic regions

A bactéria Xylella fastidiosa vem causando problemas para a cafeicultura, uma vez que sua presença, associada a diversos fatores de estresse, provoca um decréscimo na produção devido à diminuição no número e tamanho dos frutos e à morte de alguns ramos. Este trabalho objetiva avaliar o efeito da X. fastidiosa sobre cultivares de Coffea arabica (enxertados ou não) através da quantificação da proporção de vasos do xilema obstruídos pela bactéria, nas diferentes partes da planta e entre ramos com e sem sintoma da doença, em experimentos desenvolvidos em diferentes regiões edafoclimáticas. Avaliou-se também a distribuição das classes de infecção nas diferentes partes da planta nos materiais genéticos estudados. Os experimentos foram instalados em 1986 em Mococa e Garça (SP) e as amostras para o estudo anatômico, retiradas em abril de 1998 e 2000 (período de estresse hídrico), respectivamente, das plantas de cafeeiros dessas áreas. Na região de Mococa, observou-se que a nervura principal e o pecíolo foram os tecidos com proporção maior de vasos do xilema obstruídos pela X. fastidiosa; na região de Garça, foram o pecíolo e o caule. Não houve diferenças significativas na obstrução de elementos de vaso do xilema do cafeeiro ocasionado pela bactéria entre as duas regiões estudadas. Não houve tolerância à bactéria nos materiais genéticos, havendo no entanto variação dentro de cada um deles. Na região de Garça, nas plantas de café, observou-se alta proporção de vasos obstruídos nas raízes (3%), entretanto, não houve dano maior na parte aérea.<br>The Xylella fastidiosa bacterium causes problems to coffee cultivation because of a relationship with various stress factors, leading to reduction on coffee production by decreasing fruit number and size, as well as senescence of branches. This research aimed to evaluate the effect of Xylella fastidiosa to Coffea arabica cultivars (grafted or not) through the quantification of plugging bacterium within xylem vessels at different plant parts of plant symptomatic versus assymptomatic branches. The experiments were installed in 1986 in two different edaphoclimatic areas: Mococa and Garça, State of São Paulo, Brazil. The distribution of infection class was determined in different plant parts of genetic materials in study. The samples for anatomic studies were analyzed at stress hidric periods of April 1998 and 2000, respectively. The midvein and petiole in Mococa region showed more obliterated xylem vessels with X. fastidiosa than in Garça were the petiole and stem were the tissues parts more affected. There were not significant differences on bacterium coffee effect between the two studied regions. Also, bacterium tolerance did not show difference among genetic materials. However, variations within each one of them did existed. In Garça region, the coffee plants exhibited the highest proportion of obliterated vessels in root (3%), which was not translated in disease severity in the aerial part