XYL-EID · Determinants of Xylella fastidiosa host specificity

Determinants of Xylella fastidiosa host specificity

The plant pathogenic bacterium Xylella fastidiosa poses a serious threat to agriculture in Europe and especially to the Mediterranean basin. It displays both a broad host range of 563 host plant species and a wide vector range of over a hundred of vector insect species (1,2). While it has been known to be present in the Americas for decades causing severe damage in several crops of economic importance such as grapes, citrus and coffee, its first confirmed detection in Europe is relatively recent. It was first described in Southern Italy (Apulia) in 2013, where it is devastating olive trees and triggering an economic, social and political crisis. Reports of the presence of different strains in France, Germany, Spain, Portugal and Northern Italy were soon to follow (3). Although X. fastidiosa infected plant species have been eradicated in Germany, this is far to be the case in some regions of Italy, France and Spain which have been officially declared areas under containment (Corsica, France; Balearic Islands, Spain; Southern Apulia, Italy) (4). The presence of several strains and even subspecies in both France and Spain points towards several introductions in these two countries. The analysis of a limited number of X. fastidiosa genes (MLST data) suggest that the outbreak in Apulia, Italy is the result of the introduction and subsequent establishment of a single strain belonging to ST53 (X. fastidiosa subsp. pauca) – which differs from the strain(s) present in Central Italy (5). These different strains are able to infect different host plant species (i.e. have different host ranges) that remain impossible to predict. Despite its importance as a plant pathogen, there are no hypotheses on the determinants of X. fastidiosa host specificity. Because of its recent introduction in Europe, where host plants as well as the environment represent novel opportunities for expansion, it is of paramount importance to learn how X. fastidiosa adapts. This information could then be used in an attempt to limit its impact where it is already present, as well as its potential threat to risk areas where it could be disseminated. This project aims to address this very important knowledge gap, notably by studying the recent adaptation of this bacterium to olive trees in Southern Italy.

Data: CORDIS, © European Union