Genomic Acquisitions in Emerging Populations of pv. Infecting Corn in the United States and Argentina.

pv. is an emerging bacterial plant pathogen that causes bacterial leaf streak on corn. First described in South Africa in 1949, reports of this pathogen have greatly increased in the past years in South America and in the United States. The rapid spread of this disease in North and South America may be due to more favorable environmental conditions, susceptible hosts and/or genomic changes that favored the spread. To understand whether genetic mechanisms exist behind the recent spread of pv. , we used comparative genomics to identify gene acquisitions in pv. genomes from the United States and Argentina. We sequenced 41 genomes of pv. and the related sorghum-infecting pv. and performed comparative analyses against all available genomes. Time-measured phylogenetic analyses showed that pv. strains from the United States and Argentina are closely related and arose from two introductions to North and South America. Gene content comparisons identified clusters of genes enriched in corn pv. that showed evidence of horizontal transfer including one cluster corresponding to a prophage found in all pv. strains from the United States and Argentina as well as in pv. strains. In this work, we explore the genomes of an emerging phytopathogen population as a first step toward identifying genetic changes associated with the emergence. The acquisitions identified may contain virulence determinants or other factors associated with the spread of pv. in North and South America and will be the subject of future work.