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Front Plant Sci. 2016 Jul 19;7:1053. doi: 10.3389/fpls.2016.01053. eCollection 2016.

Leaf Treatments with a Protein-Based Resistance Inducer Partially Modify Phyllosphere Microbial Communities of Grapevine.

Author information

1
Department of Sustainable Ecosystems and Bioresources, Research and Innovation Centre, Fondazione Edmund MachSan Michele all'Adige, Italy; Department of Agricultural and Environmental Sciences, University of UdineUdine, Italy.
2
Department of Sustainable Ecosystems and Bioresources, Research and Innovation Centre, Fondazione Edmund Mach San Michele all'Adige, Italy.
3
Bioresources Unit, Department of Health and Environment, Austrian Institute of Technology Tulln and der Donau, Austria.
4
Technology Transfer Center, Fondazione Edmund Mach San Michele all'Adige, Italy.

Abstract

Protein derivatives and carbohydrates can stimulate plant growth, increase stress tolerance, and activate plant defense mechanisms. However, these molecules can also act as a nutritional substrate for microbial communities living on the plant phyllosphere and possibly affect their biocontrol activity against pathogens. We investigated the mechanisms of action of a protein derivative (nutrient broth, NB) against grapevine downy mildew, specifically focusing on the effects of foliar treatments on plant defense stimulation and on the composition and biocontrol features of the phyllosphere microbial populations. NB reduced downy mildew symptoms and induced the expression of defense-related genes in greenhouse- and in vitro-grown plants, indicating the activation of grapevine resistance mechanisms. Furthermore, NB increased the number of culturable phyllosphere bacteria and altered the composition of bacterial and fungal populations on leaves of greenhouse-grown plants. Although, NB-induced changes on microbial populations were affected by the structure of indigenous communities originally residing on grapevine leaves, degrees of disease reduction and defense gene modulation were consistent among the experiments. Thus, modifications in the structure of phyllosphere populations caused by NB application could partially contribute to downy mildew control by competition for space or other biocontrol strategies. Particularly, changes in the abundance of phyllosphere microorganisms may provide a contribution to resistance induction, partially affecting the hormone-mediated signaling pathways involved. Modifying phyllosphere populations by increasing natural biocontrol agents with the application of selected nutritional factors can open new opportunities in terms of sustainable plant protection strategies.

KEYWORDS:

Plasmopara viticola; Vitis vinifera; biological control; gene expression; phyllosphere microbiota; resistance induction

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