Bacterial soft rot

The initial symptom is the appearance of small, water-soaked, soft spots on the surface of the root crop, which rapidly enlarge over time.

As the infection progresses, the affected tissue turns into a foul-smelling, mushy, slimy mass due to the complete collapse of cell structure.

In many cases, the epidermis may remain intact for a short period while the entire interior of the root crop is already liquefied.

A cloudy, milky-white or yellowish bacterial ooze often exudes from the infected spots under high humidity conditions.

When sliced open, the transition between healthy and decaying tissue is often distinct but lacks a protective barrier, showing rapid disintegration.

Bacterial soft rot is primarily caused by Pectobacterium carotovorum, a gram-negative bacterium capable of degrading plant cell walls.

The pathogen secretes enzymes, specifically pectinases, which break down the middle lamella of plant cells, leading to tissue maceration.

This bacterium is a versatile pathogen with a very wide host range, affecting almost all types of succulent vegetable crops.

It survives in soil, on plant debris, and in the guts of various insects that can transmit the bacteria to healthy plant tissues.

The pathogen thrives as a facultative anaerobe, allowing it to continue destroying plant tissues even in low-oxygen environments like internal parts of tubers.

The disease is most prevalent in environments characterized by high moisture levels and moderate to warm temperatures, typically above 18°C.

Poor soil drainage and waterlogging create anaerobic conditions that inhibit plant defenses and promote the rapid multiplication of the pathogen.

Mechanical injuries sustained during harvesting, washing, or transportation are the primary routes for bacterial entry into the root tissues.

Inadequate ventilation in storage facilities, coupled with condensation on the surfaces of the vegetables, triggers rapid secondary infections.

Extreme weather conditions, such as frost damage or hail, can also cause tissue stress, making the crops highly susceptible to invasion by Pectobacterium.

The economic impact of bacterial soft rot is massive, particularly during postharvest stages where it causes rapid loss of commercial viability.

Once established in a storage bin, the disease can spread by contact from one decayed root to another, destroying entire harvests in a matter of days.

The decayed product loses all nutritional value and marketability, becoming a source of contamination for processing equipment and transport containers.

Secondary infections by other fungi and bacteria often follow, further complicating the disposal and management of affected batches.

Farmers face significant losses due to the need for immediate disposal of infected crops and the potential reduction in shelf life for the remaining stock.

Field sanitation is critical; removing and destroying crop residues significantly reduces the local population of the bacterium.

Practicing long-term crop rotation with non-host species helps to reduce the build-up of the pathogen in the soil over time.

Careful handling during and after harvest to prevent bruising or wounding of the roots is the most effective way to limit entry points.

Proper curing and drying of root crops before placing them into cold storage are essential steps to prevent initial infection and growth.

• Maintaining optimal airflow and low humidity in storage units.
• Using insect control programs to prevent wounding by pests.
• Regular cleaning and sanitizing of all storage and packing areas.