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Front. Plant Sci. | doi: 10.3389/fpls.2019.01405

Fungicides and the grapevine wood mycobiome. A case study on tracheomycotic ascomycete Phaeomoniella chlamydospora reveals potential for two novel control strategies.

  • 1Higher Institute of Agronomy, University of Lisbon, Portugal
  • 2Environmental Microbial Genomics Group (EMG), section Microbial, Ecology and Biotechnology (MEB), Department of Plant and Environmental Science (PLEN), University of Copenhagen, Denmark
  • 3Section for Environmental Microbiology and Biotechnology, Department of Environmental Sciences, Faculty of Science and Technology, Aarhus University, Denmark

Phaeomoniella chlamydospora is a tracheomycotic fungus that colonizes the xylem of grapevines (Vitis vinifera L.), causing wood discoloration, brown wood streaking, gummosis and wood necrosis, which negatively affect the overall health, productivity and lifespan of vines. Current control strategies to prevent or cope with P. chlamydospora infections are frequently ineffective. Moreover, it is unclear how fungicides commonly applied in vineyards against downy and powdery mildew agents affect the wood mycobiome, including wood pathogens such as P. chlamydospora.
In this study, we used next-generation sequencing to assess the effects of foliar spray of grapevines with inorganic (copper oxychloride and sulfur), synthetic (penconazol and fosetyl-aluminium) and natural (Blad) fungicides currently used against the downy and powdery mildews. The subjects of our investigation were (i) the resident wood mycobiome, (ii) the early colonization by a consortium of fungal wood endophytes (ACEA1), (iii) the wood colonization success of P. chlamydospora, and (iv) the in planta interaction between P. chlamydospora and ACEA1, under greenhouse conditions, in rooted grapevine cuttings cv Cabernet Sauvignon.
The data obtained suggest that the resident mycobiome is affected by different fungicide treatments. In addition, the early colonization success of the endophytes composing ACEA1 varied in response to fungicides, with relative abundances of some taxa being over- or underrepresented when compared with the control. The wood colonization by P. chlamydospora comported significant changes in the mycobiome composition and, in addition, it was greatly affected by the foliar spray with Blad, which decreased the relative abundance of this pathogen 12-fold (4.9%) when compared with the control (60.7%) and other treatments. The presence of the pathogen also decreased considerably when co-inoculated into the plant with ACEA1, reaching relative abundances between 13.9 and 2.0%, depending on the fungicide treatment applied.
This study shows that fungicides sprayed to prevent infections of powdery and downy mildews have an effect on non-target fungi that colonize the endosphere of grapevines. We suggest two potential control strategies to fight P. chlamydospora, namely the foliar spray with Blad and the use of ACEA1. Further studies to confirm these results are required.

Keywords: fungicides, Phaeomoniella chlamydospora, grapvine trunk diseases, Mycobiome, microbial ecology

Received: 20 Apr 2019; Accepted: 10 Oct 2019.

Copyright: © 2019 Del Frari, Gobbi, Aggerbeck, Oliveira, Hansen and Ferreira. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Mx. Giovanni Del Frari, Higher Institute of Agronomy, University of Lisbon, Lisbon, Portugal, gdelfrari@isa.ulisboa.pt