A vineyard in south-central Chile was surveyed during five growing seasons to analyze the increase over time in the number of plants infected with Grapevine leafroll-associated virus-1, -2 and -3. At the end of the study, GLRaV-3 was found to be the most prevalent virus, with 46% of plants infected by this pathogen. GLRaV-2 infected 13% of plants, and GLRaV-1 infected 12%. Considering all three viruses together, the prevalence of infection increased exponentially from 14% of the plants at the beginning of the study period to 68% at the end. The patterns of the spread of GLRaV-2 and GLRaV-3 were mostly along the rows, whereas the pattern of spread for GLRaV-1 could not be determined.

Un viñedo de la zona centro - sur de Chile fue monitoreado durante cinco temporadas con el objetivo de analizar el desarrollo de la epidemia de Grapevine leafroll-associated virus - 1, 2, y 3. Al final del tiempo de evaluación el GLRaV-3 resultó ser el virus más prevalente con un 46% seguido del GLRaV-2 con 13% y GLRaV-1 con 12%. Considerando los virus en su conjunto, la infección avanzó rápidamente de un 14% inicial de plantas afectadas a un 68% al final del período. El patrón de diseminación de la epidemia fue fundamentalmente en el sentido de la hileras del viñedo para los virus GLRaV-2, y -3, mientras que para GLRaV-1 no pudo ser determinado.

The transgenic plum (Prunus domestica L.) C5, in which the coat protein (CP) gene of the Plum pox virus (PPV) is inserted, represents a unique example of the use of genetic engineering for fruit crop improvement in Prunus spp. Field trials in Poland, Romania, and Spain have demonstrated resistance of C5 to several D and M strain PPV isolates. In Chile, the quarantine regulations for PPV and for genetically modified (GM) plants require that the testing of C5 for resistance to Chilean PPV isolates be done under controlled isolated conditions. To carry out these tests C5 shoots were multiplied in vitro and micro-grafted onto four Adesoto101 (Prunus insititia L.) rootstock populations that had been previously infected each with one of four Chilean PPV-Ds. Tests were carried out under controlled conditions in a biosafety greenhouse. Symptoms appearance, virus detection, and viral mRNA levels for the cylindrical inclusion (CI) and CP genes were determined during three consecutive growing seasons. Complete resistance to all PPV isolates was demonstrated during the first 2 yr in all of the C5 plants. In the third season, four of 10 C5 plants showed mild symptoms on leaves close to the graft union and low but detectable CI mRNA levels in the C5 scions. These results support the effectiveness of using of micro-grafting on P. insititia for PPV resistance studies, especially in the limited space of a quarantine facility; whereas resistance levels in C5 after 3 yr indicate the importance of long term and field scale evaluations.

El ciruelo (Prunus domestica L.) transgénico C5, que posee inserto el gen de la proteína de cubierta (CP) del Plum pox virus (PPV), es un ejemplo excepcional del uso de ingeniería genética para el mejoramiento de Prunus spp. Pruebas de campo realizadas en Polonia, Rumania y España han demostrado su resistencia a distintos aislamientos de PPV cepas D y M. En Chile, dadas las regulaciones cuarentenarias para PPV y para plantas genéticamente modificadas, los análisis de resistencia de C5 deben ser ejecutados bajo condiciones de confinamiento. Para realizar estas pruebas, se multiplicaron in vitro brotes de C5 y se microinjertaron en cuatro grupos de ’Adesoto’ 101 (Prunus insititia L.) previamente infectados con cuatro aislamientos de PPV-D chilenos ya caracterizados. Todos los ensayos se realizaron bajo condiciones controladas en invernadero de bioseguridad. Durante tres temporadas se analizó sintomatología, presencia de virus y niveles de mARN viral para los genes de la proteína de inclusión cilíndrica (CI) y CP. Durante los primeros 2 años se encontró una resistencia completa a todos los aislamientos en todos los injertos. Al tercer año, cuatro de 10 injertos C5 mostraron síntomas leves en hojas cercanas al sitio de injertación y un nivel bajo, pero detectable, de mARN de CI. Estos resultados avalan la utilidad de la microinjertación en P. insititia para estudios de resistencia a PPV, especialmente en un recinto cuarentenario, mientras que los niveles de resistencia mostrados por C5 luego de 3 años indican la necesidad de evaluaciones prolongadas y preferentemente en campo.

A presença de sintomas de 'big vein' ou engrossamento das nervuras em alface e a associação do Lettuce big-vein associated virus (LBVaV) e Mirafiori lettuce big-vein virus (MLBVV) foram verificadas por RT-PCR utilizando-se oligonucleotídeos específicos para ambos os vírus. Foram coletadas 366 plantas sintomáticas nas regiões de Bauru, Campinas e Mogi das Cruzes no estado de São Paulo nos meses de junho e setembro de 2004 e abril e julho de 2005, e 18 plantas assintomáticas na região de Mogi das Cruzes no mês de dezembro de 2004. Infecção mista do LBVaV e MLBVV foi detectada em 76,2% das plantas sintomáticas, em 11,5% somente o MLBVV foi detectado e em 6,6% somente o LBVaV. Nas plantas assintomáticas coletadas em dezembro na região de Mogi das Cruzes, em áreas de alta incidência da doença durante o inverno, foi detectada a presença de MLBVV em 9 amostras e LBVaV em 7 amostras. Quatro dessas amostras apresentaram infecção mista, indicando que o desenvolvimento de sintomas depende de fatores abióticos, como temperatura. A inoculação via extrato vegetal a partir de plantas de alface com infecção mista pelo MLBVV e LBVaV foi realizada a 16°C/ 10°C (dia/noite) e fotoperíodo de 11 horas, verificando-se que o MLBVV foi transmitido para Nicotiana tabacum TNN, N. rustica, N. occidentalis, Chenopodium quinoa e para as cultivares de alface Trocadero e White Boston, enquanto o LBVaV foi transmitido apenas para a alface White Boston. Entretanto, nenhuma destas plantas apresentou sintomas da doença, com exceção de C. quinoa que apresentou sintomas de lesões locais. Plantio em solo proveniente de áreas com histórico da doença de Mogi das Cruzes permitiu a transmissão do LBVaV para alface cv. White Boston e do MLBVV para alface cv. Trocadero e White Boston, embora apenas a cv. White Boston tenha apresentado sintomas da doença. Em conjunto, estes resultados demonstram a dificuldade de transmissão de ambos os vírus, mesmo em condições de laboratório.

The occurrence of big vein disease symptoms and the association of Lettuce big-vein associated virus (LBVaV) and Mirafiori lettuce big-vein virus (MLBVV) was evaluated by RT-PCR using specific primers for both viruses. A total of 366 symptomatic plants were collected during June and September 2004 and during April and July 2005 at Bauru, Campinas and Mogi das Cruzes in São Paulo state, and 18 symptomless plants were collected in Mogi das Cruzes on December 2004. Mixed infection was detected in 76,2% of the symptomatic plants, 11,5% had only MLBVV and 6,6% had only LBVaV. In the symptomless plants collected in areas with high incidence of the disease throughout the winter, MLBVV was found in 9 plants and LBVaV in 7 plants. Four plants had both viruses, indicating that symptom development depends on abiotic factors, such as temperature. Plants with MLBVV and LBVaV (mixed infection) were used as source of virus in a host range assay at 16C/ 10°C (day/ night) and 11h light period. MLBVV was transmitted to Nicotiana tabacum TNN, N. rustica, N. occidentalis, Chenopodium quinoa and lettuce cv. Trocadero and White Boston, while LBVaV was transmitted only to lettuce cv. White Boston. No symptons could be verified for these plants with the exception of C. quinoa that showed local lesions. Transmission through soil in areas with high incidence of the disease was observed for LBVaV to lettuce cv. White Boston and MLBVV for lettuce cv. Trocadero and White Boston, but only cv. White Boston showed symptoms. Together, these results demonstrate the difficulties in transmitting both viruses, even under controlled laboratory conditions.