Pseudomonas serbiensis sp. nov. isolated from watermelon and muskmelon in Serbia

Six <i>Pseudomonas</i> strains isolated from muskmelon and watermelon seedlings affected by stem rot and wilting in Serbia were reported as <i>P. cichorii</i> based on pathogenicity, LOPAT and cell wall fatty acid analyses. Recent bacterial isolates from cucurbit crops displaying <i>P. cichorii</i>-like symptoms in Alabama, USA, were identified as <i>P. capsici</i>, prompting polyphasic re-evaluation of the Serbian strains. All six strains were found to cause severe disease in watermelon and squash seedlings under greenhouse conditions. Strains KFB 138 and KFB 140 underwent whole-genome sequencing and were found to have the highest level of 16S rRNA similarity to <i>P. lijiangensis</i> LJ2^T (both 99.87%). Phylogenies based on housekeeping genes and core-genome analysis placed both strains into phylogroup 11 of the <i>Pseudomonas syringae</i> species complex, with KFB 138 forming a lineage basal to all other phylogroup 11 members. In core-genome phylogeny, KFB 140 was placed into a clade alongside <i>P. lijiangensis</i> LJ2^T. Average nucleotide identity based on blast (ANIb) identified KFB 140 as a member of <i>P. lijiangensis</i> (95.85%), though KFB 138 did not produce an ANIb value over 95% to any <i>Pseudomonas</i> type strain to which it was compared. Values for <i>in silico</i> DNA-DNA hybridization for both strains were below 70% to all reference strains tested, though KFB 140 was found to be most similar to <i>P. lijiangensis</i> (68.2%). KFB 138 and KFB 140 were further characterized using the online Type Genome Server, biochemical profiling with the Biolog Gen III MicroPlate system, matrix-assisted laser desorption/ionization time of flight mass spectrometry and imaged with transmission electron microscopy. From the results of the above analyses, we conclude that KFB 140 is a member of the species <i>P. lijiangensis</i> and that KFB 138 represents a novel <i>Pseudomonas</i> species, for which we propose the name <i>Pseudomonas serbiensis</i> (KFB 138^T, NCPPB 4762=LMG 33366), named for its location of isolation.