Catia Pinto will support her thesis on October 23, 2017 at the University of Aveiro, Portugal.

This thesis, co-supervised by the URCA-URVVC, the University of Aveiro and the Instituto Biocant (Portugal), deals with "Vine microbiome: an in-depth analysis of the natural microbial community of Vitis vinifiera L.".

His thesis was co-encoded by Fontaine Florence (URCA) and Catarina Gomès (Biocant).

ABSTRACT

Vitis vinifera L. is a widely cultivated fruit crop, that naturally harbours a complex microbial ecosystem or plant microbiome, such as neutral, phytopathogenic or beneficial microorganisms. Among phytopathogens, those implied in Grapevine Trunk Diseases (GTDs) are responsible for the most destructive diseases worldwide, and currently no highly effective treatments are available. Beneficial microorganisms (BCAs) may play specific roles on plant protection against phytopathogens though, the present challenge is to understand how such BCAs interact with plant and their biotechnological potential for development of innovation strategies. In this context, the aim of this study was firstly to unveil the microbial communities associated with grapevine along its growth cycle until wine fermentation and, secondly, to better understand the grapevine – BCAs – GTDs interactions. Two potential BCAs isolated from grapevine were tested against Botryosphaeriaceae species and then deep characterized, namely for their colonisation potential, induction of defence mechanisms in grapevine, in the presence or not of D. seriata F98.1, and their genome analysis.

Results showed that grapevine microbiome was very dynamic along the growth cycle. As expected, the microbial biodiversity was higher in soils, and these microbial communities differed significantly from those of leaves and wine musts. A proportion of microbial communities was shared within these structures, suggesting the existence of a core microbiome. Several isolates were then obtained from grapevine and some of them significantly decreased in vitro the mycelium growth of several Botryosphaeriaceae species, such as Fito_S127B and Fito_F278 strain which were highly effective and thus selected as potential BCAs. These strains showed to produce a high range of extracellular enzymes with biocontrol value, and were able to successfully colonize grapevine: Fito_S127B was an epiphyte from rhizosphere, while Fito_F278 colonised grapevine from roots to leaves. The artificial inoculation of green stems with D. seriata F98.1 on cutting plants showed that the necrotic lesions length caused by the pathogen was significantly reduced by Fito_S127B, in contrast to Fito_F278, which was less effective. Furthermore, these BCAs activated some specific defence responses of grapevine, allowing a more rapid and solid response of plant against the pathogen. The genome analysis also showed that these BCAs strains are an important source of bioactive compounds of biocontrol value.

Overall, this study brought new insights on the structure of microbial communities of grapevine and their interactions. Moreover, highlighted that grapevine is a natural source of microorganisms with a promising biocontrol against GTDs, and that they can promote plant defence responses. Thus, these findings provide not only a better understand of the grapevine- BCAs- GTDs interactions but also a strong contribution to future GTDs management strategy.