Complete circularized genome resources of seven strains of Xylella fastidiosa subsp. fastidiosa using hybrid assembly reveals unknown plasmids.

Abstract

Xylella fastidiosa (Xf) is a vascular plant pathogenic bacterium native to the Americas that is causing significant epidemics and economic losses in olive and almonds in Europe, where it is a quarantine pathogen. Since its first detection in 2013 in Italy, mandatory surveys across Europe revealed the presence of the bacterium also in France, Spain, and Portugal. Combining ONT and Illumina sequencing data, we assembled high-quality complete genomes of seven Xf subsp. fastidiosa strains isolated from different plants in Spain, the USA, and Mexico. Comparative genomic analyses discovered differences in plasmid content among strains, including plasmids that had been overlooked previously when using Illumina sequencing platform alone. Interestingly, in strain CFBP8073, intercepted in France from plants imported from Mexico, three plasmids were identified, including two (plasmid pXF-P1.CFBP8073 and pXF-P2.CFBP8073) not previously described in X. fastidiosa, and one (pXF5823.CFBP8073) almost identical to a plasmid described in a Xf strain from citrus. Plasmids found in the Spanish strains here were similar to those described previously in other strains from the same subspecies and ST1 isolated in the Balearic Islands and the USA. The genome resources from this work will assist in further studies on the role of plasmids in the epidemiology, ecology, and evolution of this plant pathogen.