Bacteria in a wood fungal disease: characterization of bacterial communities in wood tissues of esca-foliar symptomatic and asymptomatic grapevines.

Emilie Bruez,Jessica Vallance,Lucia Guerin-Dubrana,Maryam T Alou,Stéphane Compant,Rana Haidar,Patrice Rey,Marc Fermaud,Christophe Bertsch,Alain Deschamps,Flore Mazet

doi:10.3389/fmicb.2015.01137

Abstract

Esca is a grapevine trunk disease (GTD) associated with different pathogenic fungi inhabiting the woody tissues. Bacteria can also be found in such tissues and they may interact with these fungal colonizers. Although such types of microbial interactions have been observed for wood diseases in many trees, this has never been studied for grapevine. In this study, the bacterial microflora of different vine status (esca-symptomatic and asymptomatic), different anatomical part (trunk and cordon) and different type of tissues (necrotic or not) have been studied. Based on Single Strand Conformation Polymorphism (SSCP) analyses, data showed that (i) specific complexes of bacterial microflora colonize the wood of both necrotic and non-necrotic tissues of esca-foliar symptomatic and asymptomatic vines, and also that (ii) depending on the anatomical part of the plant, cordon or trunk, differences could be observed between the bacterial communities. Such differences were also revealed through the community-level physiological profiling (CLPP) with Biolog EcoplatesTM. Two hundred seventeen bacterial strains were also isolated from plant samples and then assigned to bacterial species based on the 16S rRNA genes. Although Bacillus sp. and Pantoea agglomerans were the two most commonly isolated species from all kinds of tissues, various other taxa were also isolated. Inoculation of vine cuttings with 14 different bacterial species, and one GTD fungus, Neofusicoccum parvum, showed no impact of these bacteria on the size of the wood necroses caused by N. parvum. This study showed, therefore, that bacterial communities differ according to the anatomical part (trunk or cordon) and/or the type of tissue (necrotic or non-necrotic) of wood of grapevine plants showing external symptoms of esca disease. However, research into bacteria having a role in GTD development needs further studies.

Highlights

Viticulture is confronted with major challenges in the form of global climate change, grapevine trunk diseases (GTDs: esca, Eutypa and Botryosphaeria dieback), and strong consumer demand for environmentally friendly viticulture
GTDs and esca have been known since antiquity but, over the last two decades, they have become a subject of major concern for the wine industry
The Single Strand Conformation Polymorphism (SSCP) profiles of the 29 samples that represent the combination of different vine status, anatomical part and tissue status revealed a complex of bacterial communities based on the number of peaks and the relative height of the baseline

Summary

Introduction

Viticulture is confronted with major challenges in the form of global climate change, grapevine trunk diseases (GTDs: esca, Eutypa and Botryosphaeria dieback), and strong consumer demand for environmentally friendly viticulture. GTDs and esca have been known since antiquity but, over the last two decades, they have become a subject of major concern for the wine industry. Esca attacks the perennial organs of the plants, producing extensive wood necroses in the trunk and cordon. According to Hofstetter et al (2012), the cost of replacing plants affected by GTDs exceeds, worldwide, 1.132 billion euros per year. The etiology of the disease, still remains poorly understood. It is not even known whether microbes, other than fungi, could interact in planta with GTD-associated agents, nor what exactly such types of microorganisms are

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Conclusion