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

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. is a recurring nuisance. This bacterial pathogen has recently emerged in novel geographic locations infecting a breadth of host plants. An introduction of subsp. 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 (). In this study, we demonstrated that the introduced strains do not persistently infect . Furthermore, we did not observe an overall increase in the virulence of the introduced strains towards coffee, indicating a lack of hypervirulence. Then, using subsp. 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.