# A pathogen of good taste: genetics of a bacterial host jump of the plant pathogen Xylella fastidiosa from coffee to wine grapes

## TL;DR

This study explores how the plant pathogen Xylella fastidiosa adapted to jump from coffee to grapevines in the USA, showing genetic changes linked to this host shift.

## Contribution

The study identifies specific genes and SNPs associated with the host jump of Xylella fastidiosa from coffee to grapevines.

## Key findings

- Introduced X. fastidiosa strains do not persistently infect coffee plants.
- Genetic analysis revealed genes and SNPs linked to adaptation in grapevines.
- The host jump to grapevines involved genetic adaptation following introduction to the USA.

## Abstract

When pathogens are repeatedly introduced into new environments, host jumps may occur into naïve taxa. Given the magnitude of the global plant trade, this process can lead to frequent disease emergence as interactions between previously isolated pathogens and new plant hosts become possible. Xylella fastidiosa is a recurring nuisance. This bacterial pathogen has recently emerged in novel geographic locations infecting a breadth of host plants. An introduction of X. fastidiosa subsp. fastidiosa from Central America to the USA several hundred years ago has since been the source of outbreaks across the globe. In the USA, particularly in California, the introduced bacterium is frequently found in European grapevine (Vitis vinifera). In this study, we demonstrated that the introduced strains do not persistently infect Coffea arabica. Furthermore, we did not observe an overall increase in the virulence of the introduced strains towards coffee, indicating a lack of hypervirulence. Then, using X. fastidiosa subsp. fastidiosa whole-genome sequences, 15 from the source region of Costa Rica and 289 from the introduced clade, we tested for traces of adaptation to grapevines. We found both genes and SNPs that are associated with the host shift to grapevines. These results support the hypothesis that a host jump with genetic adaptation occurred following the introduction of the pathogen into the USA.