A new variant of Xylella fastidiosa subspecies multiplex detected in different host plants in the recently emerged outbreak in the region of Tuscany, Italy

Maria Saponari,Raied Abou Kubaa,Giuliana Loconsole,Giusy D’Attoma,Giuseppe Altamura,Donato Boscia,Domenico Rizzo,Stefania Zicca

doi:10.1007/s10658-019-01736-9

Abstract

The vector-borne bacterial pathogen Xylella fastidiosa is widely distributed in the Americas; in the last decade it has emerged as a serious threat for agricultural crops, natural environment and landscape in Europe. Following the first EU outbreak in 2013 in southern Italy, associated with a severe disease in olive trees, annual mandatory surveys are now in place in the Member States, leading to the discovery of bacterial outbreaks in different countries. Among the latest findings, an outbreak has been reported in the Italian region of Tuscany, with infections identified in seven different plant species. In this work, we report the isolation and the genetic characterization of isolates associated with this newly discovered outbreak. Multilocus sequence typing approach revealed the occurrence of isolates harbouring a new sequence type, denoted ST87, genetically related to strains of subsp. multiplex, but different from the genotypes of this subspecies previously characterized in Europe. Five cultured strains were successfully recovered from four of the seven host plants, an important achievement for advancing the studies on genomics and pathogenicity of these isolates and thus assess their potential threat for European agriculture.

Highlights

The vector-borne bacterial pathogen Xylella fastidiosa is widely distributed in the Americas; in the last decade it has emerged as a serious threat for agricultural crops, natural environment and landscape in Europe
The number of available draft and complete genomes of X. fastidiosa are rapidly increasing, assessment of its genetic diversity is still principally based on Multilocus sequence typing (MLST) approach (Scally et al 2005; Yuan et al 2010), that allows bacterial genotypes clustering into four major subspecies: fastidiosa, multiplex, pauca and sandyi
International movements of infected plants for commercial or landscape planting are most likely the main pathway that contributed to the spread and establishment of X. fastidiosa outside of the Americas, where the pathogen was thought to be confined until the last twenty years, when the presence of the bacterium was reported in Taiwan, Iran and in several outbreaks detected in the European countries (Saponari et al 2013; Denancé et al 2017; Olmo et al 2017; EFSA PLH Panel, 2018)

Summary

Introduction

The vector-borne bacterial pathogen Xylella fastidiosa is widely distributed in the Americas; in the last decade it has emerged as a serious threat for agricultural crops, natural environment and landscape in Europe. The number of available draft and complete genomes of X. fastidiosa are rapidly increasing, assessment of its genetic diversity is still principally based on Multilocus sequence typing (MLST) approach (Scally et al 2005; Yuan et al 2010), that allows bacterial genotypes clustering into four major subspecies: fastidiosa, multiplex, pauca and sandyi.

Results

Conclusion