Bacterial ring rot of potato

Bacterial ring rot is a serious plant disease caused by the gram-positive bacterium Clavibacter sepedonicus. It is a highly contagious vascular disease that affects potato plants worldwide. Due to its potential to cause severe economic losses and its persistence in the environment, it is classified as a quarantine pathogen in many regions, necessitating strict regulatory oversight.

The primary host for this pathogen is the potato (Solanum tuberosum). The bacterium colonizes the xylem vessels, disrupting the plant's ability to transport water and nutrients. It does not survive well in the soil on its own, but it thrives in infected plant debris, tubers left in the ground, and on contaminated surfaces such as harvesting equipment, storage containers, and handling tools.

Symptoms on the foliage usually manifest as wilting of one or more stems, often appearing late in the growing season. The leaves may turn yellow and curl at the edges before eventually drying up. The most diagnostic signs are found within the tubers: when cut, the vascular ring displays a soft, creamy-yellow to brown discoloration, which later turns into a mushy, odourless decay.

Environmental conditions play a significant role in the spread of the disease. While the bacteria can survive across a range of temperatures, warm and moist conditions during the growing season favour their rapid multiplication and systemic spread throughout the plant. Transmission primarily occurs through contact between healthy and infected tubers, as well as through contaminated tools used for cutting seed potatoes or harvesting.

The economic impact of bacterial ring rot is devastating because it leads to total loss of marketability of the infected tubers and can ruin an entire harvest in storage. Effective management strategies focus on prevention: strict adherence to using certified pathogen-free seed potatoes, rigorous sanitation of all farming equipment, and implementing long-term crop rotation cycles. Once the disease is introduced, eradication is extremely difficult and requires comprehensive farm-level sanitation protocols.