Search

Olea europaea (L.) trees displaying leaf scorching symptoms, identical to those recently reported for olive trees colonized by Xylella fastidiosa in Southern Italy and also in Argentina, were observed in commercial orchards of two counties in Southeastern Brazil. PCR-based diagnosis using conserved primers for X. fastidiosa strains (RST31/33) and also specific to X. fastidiaosa subsp. pauca (CVC1/272-2 int) were positive for all symptomatic tested samples (n = 8 of 9), but no template was obtained using twigs from asymptomatic trees (n = 20). Bacterial colonies were isolated from symptomatic tissues on culture medium and confirmed by PCR using the set of primers specific to X. fastidiosa subsp. pauca. Comparative sequence analyses of seven MLST loci amplified from one tripled passaged colony (MFG01) perfectly matched with sequences of alleles leuA #7, petC #6, malF#8, cysG#10, holC#11, nuoL#8, and gltT#8, the allelic profile of Sequence Type-ST16, which is represented by the strain COF0238 isolated from Coffea arabica (L.) in Brazil (http://pubmlst.org/xfastidiosa/). Phylogenetic analysis placed the ST16 into subspecies pauca, but genetically closer to ST11 and ST13, both obtained from Citrus sinensis (L.) trees with citrus variegated chlorosis. The results confirm the association of olive plants showing leaf scorching with the presence of X. fastidiosa subsp. pauca , and represent the first report of this bacterium in Brazilian olive orchards., Phytopathologia mediterranea, 55 (1), ISSN:0031-9465, ISSN:1593-2095

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) As consequence of the recent occurrence of the disease known as Olive Quick Decline Syndrome (OQDS), caused by Xylella fastidiosa subsp. pauca (Xf-p), in olive trees (Olea europaea) there is a lack of scientific information about the biology of this pathogen in olive trees that can help to understand this pathogen and support discussions about management strategies. From these numerous gaps in the practical knowledge of this pathogen, this work has as objectives: 1. to evaluate the occurrence of vertical transmission of the bacterium; 2. to determine the distribution of Xf-p in plants with different degrees of severity; and 3. to establish a low-cost diagnostic method with the possibility of execution "in farm". Olive branches taken from an asymptomatic plant, but infected with Xf-p, were propagated in a greenhouse and the resulting seedlings were analyzed for the presence of the pathogen by real-time quantitative PCR (q-PCR). The estimated vertical transmission rate at 32 months was 57.74% (41 of 71 nursery plants) and only one plant of the 28 Xf-p-infected (0.014%) showed symptoms of OQDS. To achieve the second objective, samples from 3 plants of the cultivar 'Grapollo' showing low OQDS severity (only one branch with symptoms) and one with symptoms generalized throughout the canopy (high severity) were collected at different positions in the canopy and root system and analyzed for the presence of Xf-p by qPCR. Even under conditions of low ORDS severity positive diagnoses for Xf-p were obtained between 30% and 57% of the samples collected on asymptomatic branches, while on symptomatic branches 77% of the samples were positive. On the other hand, in plants with high incidence of OQDS 82 to 100% of samples were positive. Finally, the diagnostic method based on printing of branch extracts on nitrocellulose membranes and identification of Xf-p by serology (Tissue-Print: TP - objective 3) showed promise, but with needs for improvement since the agreement of the results between TP and qPCR techniques was only slightly partial (K = 0.01 to 0.20) according to the Cohen-Kappa index. Face a recente ocorrência da doença conhecida como Dessecamento Foliar das Oliveiras (DFO), causada por Xylella fastidiosa subsp. pauca (Xf-p), em oliveiras (Olea europaea) existe uma carência de informações científicas quanto a biologia deste patógeno em oliveira e que possam auxiliar no entendimento desse patossistema em suporte as discussões sobre estratégias de manejo. A partir dessas inúmeras lacunas sobre o conhecimento de ordem prática desse patossistema, este trabalho tem como objetivos; 1. avaliar a ocorrência de transmissão vertical da bactéria; 2. determinar a distribuição da Xf-p em plantas com diferentes graus de severidade; e 3. estabelecer um método de diagnóstico de baixo custo e com a possibilidade de execução "in farm". Ramos de oliveira retirados de uma planta assintomática, porém infectada com Xf-p, foram propagados em casa- de-vegetação e as mudas oriundas analisadas para presença do patógeno através de PCR quantitativo em tempo real (q-PCR). A taxa de transmissão vertical estimada aos 32 meses foi de 57,74% (41 de 71 mudas) e somente em uma planta das 28 positivas (0,014%) foi observado sintomas da DFO. Para se atingir o segundo objetivo, amostras de 3 plantas da cultivar “Grapollo” apresentando baixa severidade da DFO (apenas um ramo com sintomas) e uma com sintomas generalizados por toda a copa (alta severidade) foram coletadas em diferentes posições da copa e do sistema radicular e analisadas para a presença de Xf-p através de qPCR. Mesmo em condições de baixa severidade da DFO diagnósticos positivos para Xf-p foram obtidos entre 30 a 57% das amostras coletadas em ramos assintomáticos, enquanto que nos ramos sintomáticos 77% das amostras foram positivas. Por outro lado, em plantas com alta incidência da DFO 82 a 100% das amostras foram positivas. Finalmente, o método de diagnóstico baseado em impressões de estratificação de ramos em membranas de nitrocelulose e identificação de Xf-p por meio de serologia (Tissue-Print: TP - objetivo 3) mostrou-se promissor, porém com necessidades de aprimoramento uma vez que a concordância dos resultados entre as técnicas de TP e qPCR foi apenas levemente parcial (K = 0,01 a 0,20) segundo o índice de Cohen-Kappa.