Comparative genomics of Minnesotan barley-infecting Xanthomonas translucens shows overall genomic similarity but virulence factor diversity

Abstract

Xanthomonas translucens pv. translucens (Xtt) is a global barley pathogen and a concern for resistance breeding and regulation. Long-read whole genome sequences allow in-depth understanding of pathogen diversity. We have completed long-read PacBio sequencing of two Minnesotan Xtt strains and an in-depth analysis of available Xtt genomes. We found that average nucleotide identity(ANI)-based approaches organize Xtt strains differently than the previously standard MLSA approach. According to ANI, Xtt forms a separate clade from Xanthomonas translucens pv. undulosa and consists of three main groups which are represented on multiple continents. The global distribution of Xtt groups suggests that regulation of seed is not important for prevention of Xtt spread. Some virulence factors, such as 17 Type III-secreted effectors, are highly conserved and offer potential targets for the elicitation of broad resistance. However, there is a high degree of variation in virulence factors meaning that germplasm should be screened for resistance with a diverse panel of Xtt.