First report of Pectobacterium versatile causing potato soft rot in Oregon and Washington

Authors: MA, XING - Cornell University; BRAZIL, JESSIE - Oregon State University; Rivedal, Hannah; PERRY, KEITH - Cornell University; FROST, KEN - Oregon State University; Swingle, Bryan

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/6/2021
Publication Date: 3/11/2022
Citation: Ma, X., Brazil, J., Rivedal, H.M., Perry, K.L., Frost, K., Swingle, B.M. 2022. First report of Pectobacterium versatile causing potato soft rot in Oregon and Washington. Plant Disease. https://apsjournals.apsnet.org/doi/epdf/10.1094/PDIS-08-21-1635-PDN.
DOI: https://doi.org/10.1094/PDIS-08-21-1635-PDN

Interpretive Summary: Potato plants are sensitive to rotting diseases caused by bacteria. These diseases can kill plants in the field or cause the tubers to rot while they are in storage or after they are planted. In many cases, these diseases are spread accidentally when infected seed tubers are sold and shipped to farms that grow potatoes for commercial production. We have been sampling diseased potato plants from different regions of the United States to determine the types of bacteria that cause these diseases. In this study we identified a newly described species of bacteria (Pectobacterium versatile) in rotting seed tubers originating from fields in Washington and Oregon. This is an important finding because this species of bacteria was not previously known to be present in this part of the world and helps us determine the distribution and threat that these bacteria pose to potato cropping systems.

Technical Abstract: Pectobacterium and Dickeya bacteria are broad host range pathogens that are especially problematic in potato production. These bacteria, classified as soft rot Pectobacteriaceae (SRP), cause soft rot disease of tubers and blackleg or areal stem rot on the stems and leaves. There has been an increase of these diseases caused by especially virulent strains of SRP in many potato growing regions of the United States. We conducted a survey to determine the range of bacteria responsible for these diseases in Oregon and Washington during the 2019 growing season. We isolated bacteria from tubers with soft rot disease symptoms using standard methods for SRP, and determined the identity of these bacteria using DNA sequence analysis. We found that a newly described species (Pectobacterium versatile) was responsible for tuber soft rot in Oregon and Washington. We confirmed the pathogenicity of these isolates by inoculating healthy potato tubers and stems and compared the disease symptoms that developed to the symptoms caused by a virulent reference strain (positive control) and mock infection with sterile bacterial growth medium. The virulence of both isolates was similar to that of the positive control. The bacteria were reisolated from the margins of diseased tissue and confirmed by DNA sequence analysis to be identical to the original inoculum, thereby completing Koch’s postulates. To our knowledge, this is the first report of potato soft rot caused by P. versatile in Oregon and Washington, two important potato producing states.