Potato blackleg

Potato blackleg is a destructive bacterial disease primarily caused by the pathogen Pectobacterium atrosepticum (syn. Erwinia carotovora). Systematically, this pathogen belongs to the domain Bacteria, the genus Pectobacterium. These are rod-shaped, gram-negative bacteria that thrive in moist conditions and secrete enzymes capable of degrading plant cell wall pectin, resulting in soft rot symptoms.

The disease affects potatoes throughout their growth cycle, from the initial sprout emergence to storage. Characteristic symptoms include a dark, water-soaked, and necrotic decay at the base of the stem, often spreading upwards. Above ground, the foliage may wilt and turn yellow. Below ground, tubers show wet, foul-smelling rot, which can cause significant storage losses if contaminated tubers are not culled.

The life cycle of the bacteria begins within infected seed tubers, which serve as the primary reservoir for inoculum. When planted in wet, cold, or poorly aerated soil, the bacteria multiply rapidly and colonize the stems. Environmental conditions play a critical role, as high humidity and temperatures between 18°C and 25°C provide the ideal environment for the pathogen to thrive and spread throughout the field.

Dissemination often occurs through physical contact with infected tissues, contaminated agricultural machinery, or movement of surface water during heavy rain. Insect vectors also contribute to the spread by feeding on plant tissues and creating entry wounds for the bacteria. Once established in the field, the bacteria can persist in the soil for limited periods or remain latent in subsequent generations of tubers.

Effective management strategies require an integrated approach:

• planting only high-quality, certified disease-free seed tubers;
• ensuring adequate soil drainage to prevent waterlogging;
• avoiding mechanical injury during cultivation and harvest;
• maintaining strict sanitation practices in storage facilities;
• employing crop rotation with non-host plants to reduce soil-borne inoculum.