Plant Microbiome and Its Link to Plant Health: Host Species, Organs and Pseudomonas syringae pv. actinidiae Infection Shaping Bacterial Phyllosphere Communities of Kiwifruit Plants.

Witoon Purahong,Vania Michelotti,Antonio Cellini,Giorgia Perpetuini,Antonella Lamontanara,Luigi Orrù,Francesco Spinelli,Gianni Tacconi,Irene Donati

doi:10.3389/fpls.2018.01563

Witoon Purahong, Vania Michelotti + Show 7 more

Open Access

https://doi.org/10.3389/fpls.2018.01563

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Abstract

Pseudomonas syringae pv. actinidiae (Psa) is the causal agent of the bacterial canker, the most devastating disease of kiwifruit vines. Before entering the host tissues, this pathogen has an epiphytic growth phase on kiwifruit flowers and leaves, thus the ecological interactions within epiphytic bacterial community may greatly influence the onset of the infection process. The bacterial community associated to the two most important cultivated kiwifruit species, Actinidia chinensis and Actinidia deliciosa, was described both on flowers and leaves using Illumina massive parallel sequencing of the V3 and V4 variable regions of the 16S rRNA gene. In addition, the effect of plant infection by Psa on the epiphytic bacterial community structure and biodiversity was investigated. Psa infection affected the phyllosphere microbiome structures in both species, however, its impact was more pronounced on A. deliciosa leaves, where a drastic drop in microbial biodiversity was observed. Furthermore, we also showed that Psa was always present in syndemic association with Pseudomonas syringae pv. syringae and Pseudomonas viridiflava, two other kiwifruit pathogens, suggesting the establishment of a pathogenic consortium leading to a higher pathogenesis capacity. Finally, the analyses of the dynamics of bacterial populations provided useful information for the screening and selection of potential biocontrol agents against Psa.

Highlights

The plant microbiome plays a crucial role in plant health and productivity and, has received significant attention in recent years (Turner et al, 2013)
The rarefaction curves were close to saturation, suggesting that the OTUs recovered in this study nearly represented the whole bacterial genetic diversity (Supplementary Figure S1)
The present study provides a comprehensive description of the epiphytic bacterial communities on flowers and leaves of A. chinensis and A. deliciosa, the two main kiwifruit commercial species, and highlights their variability in relation to Psa infection

Summary

Introduction

The plant microbiome plays a crucial role in plant health and productivity and, has received significant attention in recent years (Turner et al, 2013). The pathogen can infect both Actinidia chinensis and A. deliciosa plants, the two most important commercial species (Donati et al, 2014). The pathogen grows on the epiphytic surfaces of Actinidia flowers and leaves. The phyllosphere represents an ecological niche with pivotal agricultural and biological significance (Whipps et al, 2008; Vorholt, 2012), and the bacterial epiphytic community can positively impact plant health, physiology and environmental fitness (Kim et al, 2011; Vorholt, 2012; Dees et al, 2015). Several epiphytic bacterial species isolated from the phyllosphere have been reported to be strong competitors against plant pathogens, acting as BCAs (Volksch and May, 2001). For the control of Psa, strains of Pseudomonas fluorescens, Bacillus subtilis, Bacillus amyloliquefaciens and, more recently, Lactobacillus plantarum have been tested as possible BCAs (Gould et al, 2015; Collina et al, 2016; Yakhin et al, 2017)

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