Morphological and molecular characterization of powdery mildew on watermelon plants in São Paulo state

Powdery mildew is one of the most commom foliar diseases of cultivated and wild cucurbits worldwide. Six different fungal species have been reported to be associated with powdery mildew of cucurbits, such as Podosphaera xanthii and Golovinomyces cichoracearum. The aim of the study was to identify the causal agent of the disease in watermelon plants (Citrullus lanatus) cultivated in greenhouses of the State of São Paulo. DNA total was extracted using Chelex method and the ITS region was amplified via standard PCR reaction using the specific primers PMITS1 and PMITS2. A fragment of 700pb was amplified and the sequence showed 99% of identity with P. xanthii (accession number JQ728480). Morphological observation showed that the conidia were ellipsoidal-ovoid, had fibrosin bodies and a bifurcated germinative tube in the lateral position. These characteristics and the molecular analyses confirmed P. xanthi as the etiological agent of powdery mildew in watermelon plants in São Paulo State. Morphological and molecular characterization of powdery mildew on watermelon plants in São Paulo statePowdery mildew is one of the most commom foliar diseases of cultivated and wild cucurbits worldwide. Six different fungal species have been reported to be associated with powdery mildew of cucurbits, such as Podosphaera xanthii and Golovinomyces cichoracearum. The aim of the study was to identify the causal agent of the disease in watermelon plants (Citrullus lanatus) cultivated in greenhouses of the State of São Paulo. DNA total was extracted using Chelex method and the ITS region was amplified via standard PCR reaction using the specific primers PMITS1 and PMITS2. A fragment of 700pb was amplified and the sequence showed 99% of identity with P. xanthii (accession number JQ728480). Morphological observation showed that the conidia were ellipsoidal-ovoid, had fibrosin bodies and a bifurcated germinative tube in the lateral position. These characteristics and the molecular analyses confirmed P. xanthi as the etiological agent of powdery mildew in watermelon plants in São Paulo State

Only the B biotype of Bemisia tabaci is present on vegetables in São Paulo State, Brazil

Bemisia tabaci (Genn.) is one of the most important pests in cultivated areas of vegetables and ornamental crops around the world. Based on the mitochondrial cytochrome oxidize I (mtCOI) sequence, there is evidence that B. tabaci should be considered a cryptic species complex of 11 groups containing 24 species. Two of the groups, Middle East-Asia Minor 1 and Mediterranean include biotypes B and Q, respectively. In this study we evaluated the mtCOI sequence of B. tabaci populations collected in sites of the state of São Paulo, Brazil. Using PCR-RFLP with Taq I, a typical biotype B profile was obtained for all specimens. Based on the comparison with mtCOI reference sequences we found four haplotypes all belonging to the Middle East-Asia Minor 1. They occurred in the hosts pepper (Capsicum annuum L.), tomato (Solanum lycopersicum L.), eggplant (Solanum melongena L.) and cucurbitaceae plants.Bemisia tabaci (Genn.) é considerada uma das mais importantes pragas em cultivos de hortaliças e ornamentais em todo o mundo. Baseado na análise da seqüência mitocondrial (citocromo oxidase I - mtCOI) foi proposto recentemente que B. tabaci deva ser considerado um complexo críptico de espécies, contendo 11 grupos e 24 espécies. Dois destes grupos: Middle East-Asia Minor e Mediterranean englobam os biótipos B e Q, respectivamente. Avaliou-se a sequência mtCOI de espécimes de B. tabaci coletados em regiões do estado de São Paulo, Brasil. Por PCR-RFLP utilizando-se a enzima Taq I, pôde-se observar somente o padrão típico de clivagem para o biótipo B. Comparando-se com sequências consenso, todas as moscas brancas foram classificadas no grupo Middle East-Asia Minor e puderam ser separadas em quatro haplótipos, indicando prevalência do biótipo B em áreas de pimentão (Capsicum annuum L.), tomate (Solanum lycopersicum L.), cucurbitáceas e berinjela (Solanum melongena L.) do Estado de São Paulo

Reaction of lettuce genotypes to Lettuce mosaic virus-Most (LMV-Most) and characterization of the translation factor eIF4E

O objetivo deste trabalho foi avaliar genótipos de alface quanto à reação ao Lettuce mosaic virus (LMV; Most-type, isolado AF-199) e variações no fator eucariótico de tradução eIF4E. Todos os genótipos inoculados foram suscetíveis ao LMV, que foi detectado por RT-PCR com primers específicos. Porém, os acessos 169501, 169501C, 172918A e 162499, apresentaram sintomas tardios e somente nas folhas inoculadas. O sequenciamento da porção codificadora para eIF4E mostrou que estes genótipos apresentam padrão eIF4E0 (mol0), típico para suscetibilidade ao LMV, o que indica que o fenótipo encontrado não está correlacionado com as variações de nucleotídeos neste fator de tradução.The objective of this work was to evaluate lettuce genotypes for their reaction to Lettuce mosaic virus (LMV; Most-type, isolate AF-199) and variations of the eukaryotic translation initiation factor eIF4E. All inoculated genotypes were susceptible to LMV, which was detected by RT-PCR using specific primer pairs. However, the accessions 169501, 169501C, 172918A, and 162499 showed late development of symptoms that appeared only on the inoculated leaves. Sequencing of the coding region of eIF4E showed that these genotypes have an eIF4E0 (mol0) standard typical for their susceptibility to LMV, indicating that the phenotype found is not correlated to nucleotide variations in this translation factor

A aplicação de fungicidas pode incrementar a produção de tomateiro coinfectado por Begomovirus e Crinivirus

The objective of this work was to evaluate the effect of fungicide application on the concentration of Tomato severe rugose virus (ToSRV, Begomovirus) in the 'Mariana' hybrid tomato coinfected with ToSRV and Tomato chlorosis virus (ToCV, Crinivirus) and the progression of viral concentration by qPCR, as well as to quantify fruit yield and quality. Experiment I consisted in the application of fungicides after sowing (pretreatment): pyraclostrobin+metiram (P+M) (at 3 g L-1) + boscalid (B) (at 0.3 g L-1), followed by biweekly sprayings with P+M (4 g L-1); in experiment II, there was no application at sowing (control treatment), only 4 g L-1 P+M biweekly. ToSRV and ToCV transmissions were performed using sweetpotato whiteflies (Bemisia tabaci, biotype B), at 15, 30, 45, 60, and 70 days after transplanting (DAT). There was an increase in yield, better fruit quality, and a reduction in the ToSRV concentration in the plants, when the viruses were transmitted late and pretreatment was performed. Tray pretreatment in sowing with P+M (3 g L-1) and B (0.3 g L-1), followed by biweekly sprayings with P+M (4 g L-1), increases fruit yield and quality in the 'Mariana' hybrid tomato coinfected at 45, 60, and 75 DAT by ToSRV and ToCV, and there is a reduction in the concentration of ToSRV.O objetivo deste trabalho foi avaliar o efeito da aplicação de fungicidas na concentração de Tomato severe rugose virus (ToSRV, Begomovirus) no híbrido de tomateiro 'Mariana' coinfectado por ToSRV e Tomato chlorosis virus (ToCV, Crinivirus) e a progressão da concentração viral por qPCR, bem como quantificar a produção e a qualidade de frutos. O experimento I consistiu na aplicação dos fungicidas após a semeadura (pré-tratamento): piraclostrobina+metiram (P+M) (a 3 g L-1) + boscalida (B) (a 0,3 g L-1), seguida de pulverizações quinzenais com P+M (4 g L-1); no experimento II, não houve aplicação na semeadura (controle), apenas 4 g L-1 de P+M quinzenalmente. As transmissões de ToSRV e ToCV foram realizadas com uso de moscas-brancas (Bemisia tabaci, biótipo B), aos 15, 30, 45, 60 e 70 dias após o transplante (DAT). Houve aumento da produção, melhor qualidade dos frutos e redução da concentração de ToSRV nas plantas, quando os vírus foram transmitidos tardiamente e o pré-tratamento foi realizado. O pré-tratamento na bandeja, na semeadura, com P+M (3 g L-1) e B (0,3 g L-1), seguido de pulverizações quinzenais com P+M (4 g L-1), aumenta a produção e a qualidade dos frutos, em tomateiro híbrido 'Mariana' coinfectado aos 45, 60 e 75 DAT por ToSRV e ToCV, e há redução da concentração de ToSRV

Localized symptoms of tomato spotted wilt virus on tomato fruits: explanation based on the study of some parameters related to disease epidemiology

Um dos aspectos curiosos do vira-cabeça do tomateiro é a multiplicidade de sintomas apresentados pelas plantas doentes. Em tomateiro de crescimento determinado, foram observados com maior frequência sintomas atípicos, ocorrendo em plantações nas regiões de Botucatu e de Presidente Prudente, SP. Os sintomas em plantas desses tomatais restringem-se aos frutos, enquanto que a parte vegetativa não apresenta sintomas visuais e não permite a recuperação do vírus através de inoculações em plantas indicadoras. Das hipóteses aventadas e testadas para explicar esse fato, ficou comprovado que a ocorrência do VVCT só no fruto do tomateiro resulta da inoculação direta de flor pelo tripes vetor virulifero, e que a maior frequência de frutos com infecção localizada em tomateiros de cultivares de crescimento determinado ocorre em função da manifestação precoce da resistência foliar de planta fisiologicamente madura em comparação com as cultivares de crescimento indeterminado, o que permite que as flores continuem a ser infectadas pelo vírus e não mais as folhas. A variabilidade observada dentro dos isolados de VVCT de frutos e demais hospedeiras não indica conclusivamente que é responsável pela infecção isolada de frutos de cultivares de crescimento determinado. Na infecção restrita aos frutos também não se constatou tendência para invasão das sementes. A espécie de tripes Frankliniella schultzei foi a predominante nos tomateiros dos ensaios e coletas realizadas nos campos experimentais e de produção na região de Botucatu, SP.The most outstanding fact revealed Tomato Spotted Wilt Virus (TSWV) is the wide range of symptoms caused in tomato plants. Symptoms of TSWV confined to young and ripe tomato fruits, but not to leaves, were observed occurring in different regions of the state of São Paulo, Brazil. The virus is recovered from the infected fruit, but not from leaves, as shown by mechanical inoculation on several host plants. The frequency of fruit infection only is greater for determinate cultivars. Through several tests it was concluded that the TSWV isolate could not account for localized fruit infection and that seeds from those fruits did not transmit the virus. Tomato flowers of determinate and indeterminate cvs can be infected by TSWV when virus-carrying Frankliniella schultzei is confined on them. Both types of tomatoes show the same degree of susceptibility to flower infection. The apparent higher frequency of plants with fruit symptoms only in determinate plants that has been recorded in field plantings and experimental is due to a mechanism of resistance associated with an earlier manifestation of mature plant resistance of determinate cultivars when compared with indeterminate ones. Thrips species Frankliniella schultzei was predominant in tomato fields in one of the studied regions

Solanum americanum: reservoir for Potato virus Y and Cucumber mosaic virus in sweet pepper crops

Weeds can act as important reservoirs for viruses. Solanum americanum (Black nightshade) is a common weed in Brazil and samples showing mosaic were collected from sweet pepper crops to verify the presence of viruses. One sample showed mixed infection between Cucumber mosaic virus (CMV) and Potato virus Y (PVY) and one sample showed simple infection by PVY. Both virus species were transmitted by plant extract and caused mosaic in tomato (Solanum lycopersicum cv. Santa Clara), sweet pepper (Capsicum annuum cv. Magda), Nicotiana benthamiana and N. tabaccum TNN, and local lesions on Chenopodium quinoa, C. murale and C. amaranticolor. The coat protein sequences for CMV and PVY found in S. americanum are phylogenetically more related to isolates from tomato. We conclude that S. americanum can act as a reservoir for different viruses during and between sweet pepper crop seasons.As plantas daninhas podem atuar como importantes reservatórios de vírus. Solanum americanum (Maria Pretinha) é uma planta daninha comum no Brasil e amostras com mosaico foram coletadas em áreas produtoras de pimentão, para verificar a presença de vírus. Uma amostra apresentou infecção mista com Cucumber mosaic virus (CMV) e Potato virus Y (PVY) e uma amostra apresentou infecção simples com PVY. As duas espécies virais foram transmitidas por extrato vegetal e ocasionaram mosaico em tomate (Solanum lycopersicum cv. Santa Clara), pimentão (Capsicum annuum cv. Magda), Nicotiana benthamiana e N. tabaccum TNN, lesões locais em Chenopodium quinoa, C. murale e C. amaranticolor. As sequências de proteína capsidial para o CMV e PVY encontradas em S. americanum estão filogeneticamente mais relacionadas com isolados de tomate. Conclui-se que S. americanum pode atuar como reservatório de diferentes vírus, durante e entre as épocas de cultivo de pimentão