Comparative genomic insights into the epidemiology and virulence of plant pathogenic pseudomonads from Turkey


Dillon M. M. , Ruiz-Bedoya T., Bundalovic-Torma C., Guttman K. M. , Kwak H., Middleton M. A. , ...More

MICROBIAL GENOMICS, vol.7, no.7, 2021 (Journal Indexed in SCI) identifier identifier identifier

  • Publication Type: Article / Article
  • Volume: 7 Issue: 7
  • Publication Date: 2021
  • Doi Number: 10.1099/mgen.0.000585
  • Title of Journal : MICROBIAL GENOMICS
  • Keywords: bacterial diseases, phytotoxins, plant pathogens, Pseudomonas fluorescens, Pseudomonas syringae, type III secreted effectors, EFFECTOR-TRIGGERED IMMUNITY, SYRINGAE PV. TOMATO, POPULATION-STRUCTURE, SPECIES COMPLEX, III EFFECTORS, LIFE-HISTORY, HOST-RANGE, 1ST REPORT, FLUORESCENS, VIRIDIFLAVA

Abstract

Pseudomonas is a highly diverse genus that includes species that cause disease in both plants and animals. Recently, pathogenic pseudomonads from the Pseudomonas syringae and Pseudomonas fluorescens species complexes have caused significant outbreaks in several agronomically important crops in Turkey, including tomato, citrus, artichoke and melon. We characterized 169 pathogenic Pseudomonas strains associated with recent outbreaks in Turkey via multilocus sequence analysis and wholegenome sequencing, then used comparative and evolutionary genomics to characterize putative virulence mechanisms. Most of the isolates are closely related to other plant pathogens distributed among the primary phylogroups of P. syringae, although there are significant numbers of P. fluorescens isolates, which is a species better known as a rhizosphere- inhabiting plantgrowth promoter. We found that all 39 citrus blast pathogens cluster in P. syringae phylogroup 2, although strains isolated from the same host do not cluster monophyletically, with lemon, mandarin orange and sweet orange isolates all being intermixed throughout the phylogroup. In contrast, 20 tomato pith pathogens are found in two independent lineages: one in the P. syringae secondary phylogroups, and the other from the P. fluorescens species complex. These divergent pith necrosis strains lack characteristic virulence factors like the canonical tripartite type III secretion system, large effector repertoires and the ability to synthesize multiple bacterial phytotoxins, suggesting they have alternative molecular mechanisms to cause disease. These findings highlight the complex nature of host specificity among plant pathogenic pseudomonads.