Bacterial canker of tomato

Systematic position and nature: Corynebacterium michiganensis, currently recognized as Clavibacter michiganensis subsp. michiganensis, is a Gram-positive, rod-shaped bacterium. It belongs to the kingdom Bacteria and the family Microbacteriaceae. This phytopathogen acts as a specialized vascular parasite that triggers systemic infections in host plants.

Diseases and host range: The primary disease caused by this pathogen is bacterial canker of tomatoes. While the bacteria can occasionally infect other solanaceous plants, the tomato is the most significant host. In tomato production, this organism is considered one of the most destructive threats due to its ability to cause total plant wilting.

Biology and life cycle: The pathogen enters plants through wounds or natural openings such as hydathodes. Once inside, it colonizes the plant's xylem vessels. The accumulation of bacterial cells and the production of extracellular polysaccharides obstruct the flow of water, leading to the characteristic wilting symptoms observed in infected plants.

Environmental conditions: The spread of the pathogen is highly dependent on environmental factors, particularly high relative humidity and temperatures ranging between +24°C and +28°C. The bacterium is highly persistent; it can survive for extended periods in crop debris, infested soil, and seeds, which serves as a major pathway for global spread.

Damage and management: The economic impact involves severe yield losses and fruit quality degradation. Control measures are primarily preventive and include:

• The use of certified disease-free seeds.
• Strict sanitation protocols for greenhouse tools and equipment.
• Disinfection of substrates and growing media.
• Systemic monitoring and rogueing of infected plants.
• Implementation of crop rotation cycles to reduce soil-borne inoculum.