Phylogeny of pectolytic bacteria associated with recent outbreaks of potato soft rot and blackleg in the United States
Carol Ishimaru: University of Minnesota
<div>Soft rot diseases of potato are caused by several taxa of bacteria belonging to the newly described family <em>Pectobacteriaceae</em>. Most soft rot bacteria formerly named as <em>Erwinia</em> spp. were reclassified into the genera <em>Pectobacterium</em> and <em>Dickeya</em>. Multiple species of <em>Pectobacterium </em>cause soft rot diseases during field production and storage of potatoes. Recently, <em>Dickeya</em> has been connected with significant losses from blackleg and non-emergence diseases in commercial and seed potato production in the Northeastern U.S. To develop a current depiction of the soft rot pathogens present in the U.S. and to re-evaluate isolate identifications made prior to taxonomic reclassifications, a phylogenetic study of a large collection of pectolytic soft rot bacteria was conducted. The collection included isolates from recent potato soft rot outbreaks around the U.S., historical isolates from academic culture collections, and reference strains from bacterial culture repositories. Phylogenies were constructed using a multilocus sequence alignment (MLSA) of 3 to 5 housekeeping genes. <em>P. carotovorum</em> subsp. <em>carotovorum</em>, <em>P. carotovorum</em> subsp. <em>brasiliensis</em> and <em>P. parmentieri </em>were common within the U.S. collection. <em>D. chrysanthemi</em>, <em>D. dianthicola</em>, <em>D. dadantii</em> were also present. The quarantine organism <em>D. solani</em> was not detected. By providing new baseline knowledge, this study can aid in monitoring future shifts in soft rot pathogens within the U.S. and inform strategies for disease management.</div>
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