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Survey of pectolytic bacteria causing blackleg and soft rot in Pennsylvania potatoes.

Amanda Mainello: The Pennsylvania State University

<div>Recent outbreaks of potato blackleg and soft rot caused by <em>Pectobacterium</em> spp. and more recently <em>Dickeya</em> spp. across the U.S. mid-Atlantic region have caused yield loss due to poor emergence as well as stem and tuber rot. In order to strategize management and to understand variables influencing pathogen diversity, we must first define the pathogens causing blackleg and soft rot in Pennsylvania (PA). No surveys have been conducted to determine the prevalence of these species associated with disease outbreaks in PA potato fields. Therefore, symptomatic potato plants were collected from PA fields in 2016 and 2017. Suspect pathogens were isolated based on their ability to grow and cause pitting on SL-CVP media. Isolates were tentatively identified based on phylogenetic relationships using neighbor-joining analyses of 16S rRNA gene sequences from all isolates as well as <em>Pectobacterium </em>and <em>Dickeya</em> spp. type strains. Various pathogenic taxa, including the dominant taxa <em>Dickeya dianthicola </em>and <em>Pectobacterium carotovorum</em> subsp.<em> carotovorum, </em>have been isolated from symptomatic plants in PA. Understanding how the diverse pectolytic bacteria associated with symptomatic blackleg potatoes in PA may be influenced by factors such as cultivar, location, season and/or soil type is the first step in developing effective management strategies.</div>