The emergence of plant pathogens is often associated with
waves of unique evolutionary and epidemiological events. Xanthomonas
hortorum pv. gardneri is one of the major pathogens
causing bacterial spot disease of tomatoes. After its first report
in the 1950s, there were no formal reports on this pathogen until
the 1990s, despite active global research on the pathogens
that cause tomato and pepper bacterial spot disease. Given the
recently documented global distribution of X. hortorum pv. gardneri,
our objective was to examine genomic diversification associated
with its emergence.We sequenced the genomes of X. hortorum
pv. gardneri strains collected in eight countries to examine
global population structure and pathways of emergence using
phylodynamic analysis.We found that strains isolated post-1990
group by region of collection and show minimal impact of recombination
on genetic variation. A period of rapid geographic
expansion in X. hortorum pv. gardneri is associated with acquisition
of a large plasmid conferring copper tolerance by horizontal
transfer and coincides with the burgeoning hybrid tomato
seed industry through the 1980s. The ancestry of X. hortorum
pv. gardneri is consistent with introduction to hybrid tomato
seed production and dissemination during the rapid increase in
trade of hybrid seeds.
Description:
DATA AVAILABILITY : The read files and genome assemblies for all strains sequenced for this study are available under NCBI bioproject PRJNA940592. Further
information for previously sequenced strains is available in Supplementary Table S1.