Rahnella rot

These microorganisms are classified as opportunistic pathogens of the Yersiniaceae family, capable of existing in soil, water, and in association with plant tissues.

The bacteria possess high enzymatic activity, enabling them to actively degrade plant polysaccharides, including the pectin substances of cell walls.

The pathogen often manifests as a secondary infection that complicates other bacterial diseases or develops against a backdrop of weakened plant immunity.

In a phytopathological context, Rahnella rot is considered a form of soft bacterial decay capable of causing systemic damage to the vascular system of crops.

The primary symptom of infection is the appearance of water-soaked spots on leaves, stems, or fruits, which rapidly increase in size.

Tissues in the affected areas take on a characteristic softened appearance, often accompanied by slimy decay and a specific unpleasant odor.

When the root system is affected, browning and necrosis of fine feeder roots are observed, leading to a sharp decrease in plant turgor.

Under conditions of high humidity, bacterial exudate in the form of cloudy droplets may appear on the surface of the lesions.

• Yellowing of the leaf margins.
• Softening of fruit at the point of attachment to the stem.
• Stunting and reduced overall vegetative development.

Disease development depends directly on the hydrothermal regime: high relative humidity levels above 80% are considered optimal conditions.

The temperature range for active multiplication of Rahnella bacteria is between 20–28°C, making the disease particularly dangerous in greenhouses.

Poor agricultural practices, including waterlogged soil and a lack of proper ventilation in protected environments, are critical risk factors.

Mechanical damage caused by pests or during field operations serves as an entry point for the initial colonization of the infection.

Standing moisture on leaf surfaces during the night creates an ideal environment for the pathogen to transition from a saprotrophic to a parasitic state.

The primary danger of Rahnella rot lies in the rapid loss of commercial value of produce, especially during storage after harvest.

Damage to the plant's vascular system leads to a blockade of water and nutrient transport, inevitably resulting in wilting and the death of the entire plant.

If seedlings are infected, Rahnella rot can destroy a significant portion of the crops in a short period, leading to serious economic losses.

The bacteria can accumulate in soil and on plant debris, creating a high infectious background for future crop rotations in the same field.

Difficulties in early-stage diagnosis often lead to delayed implementation of protective measures, rendering control efforts largely ineffective.

The foundation of prevention is strict adherence to crop rotation, ensuring that susceptible crops are not returned to the same site for at least 3–4 years.

Thorough disinfection of greenhouses, farming equipment, and storage containers is necessary, utilizing approved broad-spectrum bactericides and fungicides.

To prevent the spread of the infection, it is essential to promptly remove and destroy all plant debris showing signs of infection away from the field.

Managing the population of pests that compromise the integrity of the plant epidermis significantly reduces the risk of Rahnella infection.

The application of biological preparations based on Bacillus subtilis promotes the formation of a natural defensive barrier on the surface of plant organs.