First report of stem rot on potato caused by Dickeya chrysanthemi in Minnesota

Bacterial soft rot and black leg diseases of potato occur sporadically in the Upper Midwestern United States. Multiple members of the soft rot Enterobacteriaceae (SRE) cause diseases in potato. The taxonomy of SREs has undergone extensive revision, resulting in the establishment of new genera and species to better reflect the phylogeny and diversity of strains formerly classified as Erwinia carotovora or Erwinia chrysanthemi (Marrero et al. 2013). One such species, Dickeya dianthicola, has been associated with recent severe black leg outbreaks in the Eastern US. To identify the SREs in the Upper Midwest, a 2016 survey of commercial and seed potato fields in Minnesota and North Dakota was conducted. SREs (123) were isolated from 78 tissue samples exhibiting symptoms of black leg, stem rot and soft rot. Small tissue samples from the margin of symptomatic and healthy tissues were suspended in 0.02 M potassium phosphate buffer, pH 7.2, for 30 minutes. Cell suspensions were serially diluted and spread onto cry...