Multifunctional study of xylem-sap of Portuguese olive cultivars and its relation  with susceptibility to infection by Xylella fastidiosa

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Exploitation of plant microbiota in the development of new approaches to manage Xylella fastidiosa and its insect vectors

Publication . Cameirão, Cristina; Baptista, Paula

Xylella fastidiosa is a plant pathogen transmitted by insect vectors that cause high losses in a variety of agriculturally important crops. In Europe, an outbreak of X. fastidiosa was first detected in 2013 in olive trees in Southern Italy, being Philaenus spumarius (L.) identified as the vector involved in this outbreak. In this work, as a first approach, we explored the endophytic microbial community inhabiting plants in order to design new approaches to manage the X. fastidiosa in the olive tree and its insect vector. Nymphs of P. spumarius feeds commonly on stems of Coleostephus myconis (L.), which is a common weed found in olive groves. A better understand of the feeding effect on the fungal community residing in this weed and of the role of these fungi in feeding choice could assist in the manipulation of P. spumarius populations. For this, the endophytic fungal community of stems, leaves and inflorescences of C. myconis with three levels of P. spumarius infestation was studied by cultural dependent method. Feeding was showed to affect the fungal communities in the stem and leaf but not the ones in the inflorescence. A set of fungi was identified to be associated to either infested or non-infested plants, suggesting playing a key role on the feeding process. As a second approach, it was observed, in the outbreak, the presence of olive cultivars resistant (cv. FS17) or susceptible (cv. Kalamata) to X. fastidiosa. The study of the xylem microbiome of these two cultivars, was performed through Illumina amplicon sequencing in order to determine whether susceptibilities differences are linked to its core microbiome. Overall, the core microbiome was dominated by members of the Proteobacteria (81% of the total bacteria reads) and Ascomycota (98% of the total fungal reads). In non-infected trees, the core microbiome was found to differ between susceptible and resistant cultivars. The presence of X. fastidiosa showed to induce greater variation in microbial composition and diversity of the susceptible cultivar than of the resistant cultivar. Specific fungal/bacterial signatures were detected to either the presence or the absence of X. fastidiosa in the xylem vessels, suggesting an important role of these microorganisms in pathogen establishment/development. Our study provides microbial candidates to further evaluate their role in the management of P. spumarius and X. fastidiosa.

2019Master thesis

Restricted access

Characterization of the endophytic fungal communities associated to Coleostephus myconis: looking for potential repellent/attractant compounds towards Philaenus spumarius

Publication . Cameirão, Cristina; Fernandes, Gisela Mariana; Martins, Fátima; Pereira, J.A.; Baptista, Paula

Philaenus spumarius is a xylem feeding insect identified so far as the only vector involved in the first European outbreak of the phytobacterium Xylella fastidiosa, affecting and devastating olive groves in Italy. One approach to reduce X. fastidiosa transmission could rely in the vector control through the use of baits to attract and/or repel de insect. Fungal endophytes inhabiting plants provide a source of candidate repellent/attractant compounds. In this work, the endophytic fungi community associated to the weed Coleostephus myconis, was studied in order to identified potential fungi that can be used as attractants or repellents of P. spumarius. Coleostephus myconis is common in olive groves and preferentially used by P. spumarius for the nymph development. Fungi were isolated from the stems, leaves and inflorescences from plants with three levels of P. spumarius infestation (i.e. no infestation, moderate and high infestation). The fungal isolates obtained were identified by sequencing the ITS region of rDNA and the partial tef1. Overall, was obtained 138 taxa belonging to 37 different genera. The endophytic community composition differs between infested and non-infested plants, solely at stems level, where the P. spumarius foam nests are present. The fungal genera, Cytospora, Diaporthe and Penicillium, which are well-known with producers of volatiles compounds repellent activity against insect, were found only on non-infested plants. Botrytis was restricted to infested plants. The behavioral responses and preferences of P. spumarius for C. myconis plants colonized by these endophytes should be investigated in the future.

2018Conference object

Open access

Caracterização de potenciais doenças da oliveira e exploração de métodos de luta biológica contra a tuberculose

Publication . Candeias, Gilcimar Jesus; Baptista, Paula; Soares, Ana Cristina Fermino

A oliveira é uma cultura muito importante para a região do Mediterrâneo e Península Ibérica. Todavia, na última década, tem-se observado um aumento de incidência de potenciais novas doenças e de doenças comuns desta cultura, tais como a Tuberculose, que causam elevadas perdas ao nível da produção. O presente estudo pretende ser um primeiro contributo para: i) o conhecimento de potenciais novas doenças da oliveira e dos seus agentes causais; ii) a identificação de um novo meio de luta biológico contra a tuberculose da oliveira. Assim, de forma a atingir o primeiro objetivo, começou-se por descrever novas lesões que ocorrem com elevada incidência em ramos, folhas e frutos de oliveiras na região de Mirandela, e por caracterizar a comunidade fúngica que lhe está associada com o intuito de identificar potenciais agentes causais destas lesões. Para atingir o segundo objetivo, avaliou-se o efeito da aplicação de um consórcio de microrganismos endófitos, obtido de oliveiras centenárias com tolerância à tuberculose, na incidência e severidade da tuberculose em plântulas de oliveira. Os resultados obtidos permitiram identificar um total de sete lesões diferentes, a maioria das quais em folhas, podendo cada uma delas corresponder a uma potencial nova doença. Em três destas lesões foi identificada a presença exclusiva de espécies fúngicas (Neofabraea vagabunda, Botrytis sp., Phoma macrostoma e Cytospora pruinosa), sugerindo tratarem-se de potenciais agentes causais destas lesões. Este resultado necessita, contudo, de confirmação. A aplicação do consórcio de microrganismos endófitos em plântulas de oliveira permitiu reduzir significativamente a incidência e a severidade da tuberculose face às plantas inoculadas exclusivamente com o agente causal desta doença, Pseudomonas savastanoi pv. savastanoi. Este efeito benéfico da microbiota na oliveira revelou ser superior quando a inoculação com a microbiota ocorria previamente à inoculação com o patogénico. A utilização desta microbiota endófita poderá constituir uma estratégia inovadora na luta biológica contra a tuberculose, e cujo mecanismo de ação deverá ser estudado no futuro.

2021Master thesis

Open access