Identification and Bioinformatic Characterization of Antimicrobial Resistance Genes in Pseudomonas syringae Phylogroup 2 Associated with Bacterial Stem Blight in Alfalfa (Medicago sativa)

Pseudomonas syringae Phylogroup 2 is a Gram-negative bacterial pathogen known to cause bacterial stem blight (BSB) in alfalfa (Medicago sativa), significantly affecting crop yield and quality. This study utilized whole-genome sequencing and comprehensive bioinformatic analysis to identify antimicrobial resistance (AMR) genes in P. syringae strain Susan2139. Annotated genome sequences were processed to generate a circular genome map, identify housekeeping genes, and construct a phylogenetic tree. Tools such as CARD, MLST, and PathogenFinder were used to predict AMR genes and pathogenicity potential. The strain demonstrated the presence of efflux pump genes (adeF, AbQ) associated with resistance to fluoroquinolones and tetracyclines, but lacked plasmid-mediated or acquired virulence genes. Phylogenetic analysis placed the strain closest to P. syringae pv. syringae B64 (98.1% ANI). Pathogenicity predictions classified the bacterium as non-pathogenic to humans. These results contribute valuable insights into AMR gene evolution in phytopathogens and offer potential avenues for disease control strategies in alfalfa cultivation.