Researchers at Penn State University (PSU) have discovered new pathogen strains that could pose a threat to Pennsylvania’s tubers. Their goal is to create techniques for managing this hazard.

From 26 potato fields in Pennsylvania, the researchers removed potato stems or tubers that showed signs of soft rot or black leg, such as wilting, stunting, black lesions, and rotting tubers. These diseases, which have the potential to destroy crops, are mostly brought on by bacteria belonging to the Pectobacterium and, more recently, Dickeya species.

Six different species of Pectobacterium and one strain of Dickeya that had not before been documented in Pennsylvania were among the 456 samples of bacteria that the researchers isolated, cultivated, and identified as infecting the potatoes. Moreover, there had not been any reports of one species of Pectobacterium in the U.S. before.

The findings, according to Ph.D. Carolee T. Bull, corresponding author and professor of bacterial systematics and plant pathology, plant pathology, and environmental microbiology, may help identify and measure the pathogens responsible for soft rot and blackleg in Pennsylvania and other areas.

“In addition to surveillance, these insights could also help us better understand disease epidemiology. For example, the pathogens may have different optimum temperatures for growing or for producing these symptoms in the potatoes. So, the severity of the disease may change depending on different climate conditions,” Bull added.

While some Pectobacterium species have long been known to scientists, Bull stated that throughout the past few years, a sizable number of new Dickeya and Pectobacterium species have been discovered. Significant yield losses have also been caused by these infections recently throughout the northeastern U.S., especially in Maine and New York.

Bull stated that because of these outbreaks, there is a renewed interest in keeping an eye on pathogens that are not yet known to exist in the U.S. One such pathogen is Dickeya solani, a bacteria that has been linked to serious illness outbreaks in Europe in the past.

“The losses in the Maine potato industry, as well as the importance of the potato industry here in Pennsylvania and to the potato chip industry, necessitated that we determine what pathogens may be causing these outbreaks. We were worried that new pathogens had entered the U.S., including the very devastating Dickeya solani,” Bull added.

Among the pathogens identified were P. actinidiae, P. polonicum, P. polaris, P. punjabense, P. parmentieri, and P. versatile, marking the first time these bacteria were reported in Pennsylvania. Additionally, this was the first time P. actinidiae was reported in the entire U.S. The pathogens P. carotovorum, D. dianthicola, and P. brasiliense were also reported, which the researchers said they had expected.

In the future, the researchers said they will continue their work by testing the effects of these pathogens on potatoes, developing surveillance tools for each of these pathogens, and evaluating the need for new management practices.

Amanda M. Mainello-Land, previously a graduate research assistant at Penn State; Shaheen Bibi, previously a postdoctoral researcher at Penn State; and Beth Gugino, professor of vegetable pathology at Penn State, also co-authored the study.

The United States Department of Agriculture (USDA) and the USDA National Institute of Food and Agriculture (NIFA) helped support this research.