Pseudomonas marginalis

Pseudomonas marginalis is a gram-negative, motile rod-shaped bacterium within the Pseudomonadaceae family. It is recognized as a significant phytopathogen that primarily functions as an opportunistic parasite. This bacterium is well-known for its ability to cause severe economic losses in both field conditions and during post-harvest storage by degrading plant cell walls through enzymatic activity.

The disease caused by this pathogen is widely referred to as bacterial soft rot. It affects a broad variety of important agricultural crops, including potatoes, onions, carrots, lettuce, and various cruciferous vegetables. Infection results in the rapid maceration of plant tissues, leading to a slimy, watery, and foul-smelling decay that renders the infected vegetable products entirely unsuitable for market or consumption.

The biology and lifecycle of Pseudomonas marginalis are closely tied to environmental moisture levels. The bacteria survive in soil, decaying crop residues, and on the surfaces of seeds. They enter host plants through natural openings like stomata or through wounds caused by mechanical harvesting, handling, or pest activity. Once inside, they secrete pectinolytic enzymes that dissolve the middle lamella between cells.

Environmental conditions conducive to the development and spread of the pathogen include high relative humidity (above 85%) and moderate temperatures ranging from 15°C to 25°C. In storage facilities, poor ventilation and condensation are critical drivers of rapid spread. In the field, heavy rainfall or irrigation methods that keep foliage wet are major contributors to the dissemination of the bacterial population.

Effective control measures require an integrated approach focusing on prevention and hygiene:

• Implementation of crop rotation cycles to reduce bacterial survival in the soil.
• Proper sanitation and disinfection of storage facilities and containers before harvest.
• Maintenance of low temperatures and low humidity in vegetable storage environments.
• Control of field insects and pests that facilitate bacterial entry through wounding.
• Ensuring proper soil drainage and avoiding overhead irrigation where feasible.