Bacterial ring rot

Bacterial ring rot, caused by the phytopathogenic bacterium Clavibacter sepedonicus (formerly Corynebacterium sepedonicum), is a severe systemic disease affecting potato crops globally. Belonging to the Clavibacter genus, this organism targets the xylem tissues of the potato plant, leading to vascular breakdown and subsequent wilting of the foliage and decay of the tubers.

The primary hosts of this pathogen are potato species. Symptoms include the characteristic ring-like decay of the vascular tissue in the tuber, which becomes soft and creamy-yellow. On the plant surface, the disease appears as chlorosis of the lower leaves followed by wilting of the stems. If left unmanaged, the pathogen can result in total crop failure and significant economic losses for commercial potato producers.

The life cycle of C. sepedonicus is predominantly carried out within infected seed tubers. The bacteria survive in a dormant state inside the plant tissue during winter and reactivate when the tubers are planted. The pathogen spreads rapidly during the growing season through contact with contaminated surfaces, such as cutting knives, farm machinery, and storage containers, which act as vectors for the transmission of the bacteria between plants.

Development of the pathogen is favored by moderate to warm temperatures and high soil moisture levels. Since the bacteria colonize the xylem, they disrupt the plant's hydraulic system, which accelerates the wilting process when the crop faces heat stress or drought. Because the pathogen can remain latent in symptomless tubers, it is easily transported across long distances through international trade.

Management of ring rot relies heavily on strict quarantine protocols and hygiene practices. Control strategies include the exclusive use of certified pathogen-free seeds, routine sanitation of all agricultural equipment using approved disinfectants, and the rapid removal and destruction of any plants exhibiting suspected symptoms. Crop rotation and avoiding the use of communal cutting equipment are essential to prevent the spread of this highly contagious bacterial disease.