High genomic diversity of novel phages infecting the plant pathogen Ralstonia solanacearum, isolated in Mauritius and Reunion islands

Angélina Trotereau,Catherine Schouler,Max Jean Bernard Pécheur,Claudine Boyer,Isabelle Bornard,Clara Torres-Barceló

doi:10.1038/s41598-021-84305-7

Abstract

Bacterial wilt caused by the Ralstonia solanacearum species complex (RSSC) is among the most important plant diseases worldwide, severely affecting a high number of crops and ornamental plants in tropical regions. Only a limited number of phages infecting R. solanacearum have been isolated over the years, despite the importance of this bacterium and the associated plant disease. The antibacterial effect or morphological traits of these R. solanacearum viruses have been well studied, but not their genomic features, which need deeper consideration. This study reports the full genome of 23 new phages infecting RSSC isolated from agricultural samples collected in Mauritius and Reunion islands, particularly affected by this plant bacterial pathogen and considered biodiversity hotspots in the Southwest Indian Ocean. The complete genomic information and phylogenetic classification is provided, revealing high genetic diversity between them and weak similarities with previous related phages. The results support our proposal of 13 new species and seven new genera of R. solanacearum phages. Our findings highlight the wide prevalence of phages of RSSC in infected agricultural settings and the underlying genetic diversity. Discoveries of this kind lead more insight into the diversity of phages in general and to optimizing their use as biocontrol agents of bacterial diseases of plants in agriculture.

Highlights

Bacterial wilt caused by the Ralstonia solanacearum species complex (RSSC) is among the most important plant diseases worldwide, severely affecting a high number of crops and ornamental plants in tropical regions
There is a substantial imbalance in virtually all host–parasite interactions, with multiple parasites attacking the same host species. This is the case for bacteria and phages, but the knowledge and amount of isolated or sequenced bacteria surpass that of their natural enemies, bacteriophages[41]
This study reports a wide diversity of newly isolated R. solanacearum phages in two islands of the Southwest Indian Ocean, and demonstrates the prevalence of the parasites of this bacterium in agricultural environments affected by bacterial wilt disease

Summary

Introduction

Bacterial wilt caused by the Ralstonia solanacearum species complex (RSSC) is among the most important plant diseases worldwide, severely affecting a high number of crops and ornamental plants in tropical regions. Our findings highlight the wide prevalence of phages of RSSC in infected agricultural settings and the underlying genetic diversity Discoveries of this kind lead more insight into the diversity of phages in general and to optimizing their use as biocontrol agents of bacterial diseases of plants in agriculture. Bacteria from the Ralstonia solanacearum species complex (RSSC) are major plant pathogens, causing bacterial wilt disease in a wide range of important agricultural and wild plant h osts[1]. The complete genome of only 35 R. solanacearum phages are fully classified according to the International Committee on Taxonomy of Viruses (ICTV) guides This number is low compared, for example, to the 224 phages of Pseudomonas (comprising all bacterial species), or phages infecting human associated bacteria such. More genomic and metagenomic data of phages is helping to acquire detailed knowledge on phage ecology and evolution in varied ecosystems[15]

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Conclusion