Pseudomonas gladioli

Systematic position and general characteristics: Pseudomonas gladioli (often classified as Burkholderia gladioli) is a Gram-negative, aerobic, rod-shaped bacterium. It is a significant phytopathogen known for its ability to produce biofilms and various toxins. As an opportunistic pathogen, it is highly adaptable, surviving efficiently in the soil, on plant debris, and as an endophyte within various host tissues.

Diseases and host plants: This bacterium is responsible for several destructive diseases, including bacterial scab, soft rot, and stem rot. It primarily affects ornamental bulbous plants such as gladioli, irises, and freesias. Furthermore, it causes severe damage to essential food crops, including onions, garlic, and various Brassicaceae species, leading to significant post-harvest losses and reduced shelf life.

Biology and life cycle: The pathogen overwinters in infested soil, infected bulbs, corms, and plant debris. Infection typically occurs through natural openings like stomata or via mechanical wounds caused by cultivation or insect damage. Once established, the bacteria spread rapidly within the host tissue, facilitated by irrigation water, splashing rain, and contaminated agricultural tools used during routine maintenance.

Conditions for development and economic impact: The development of the disease is highly correlated with high humidity levels and moderate temperatures between 20°C and 28°C. The economic impact is profound, as the infection causes unsightly lesions, tissue necrosis, and complete rotting of bulbs. In storage, the pathogen can spread rapidly from infected units to healthy ones, leading to massive financial losses for commercial growers.

Measures of protection and control: Managing Pseudomonas gladioli requires a multi-faceted approach to limit the inoculum and prevent spread:

• Selection and quarantine of disease-free planting stock.
• Regular disinfection of all gardening and harvest equipment.
• Strict adherence to crop rotation cycles to reduce soil-borne pathogen load.
• Implementation of low-humidity storage environments to inhibit bacterial growth.
• Application of copper-based bactericides or biocontrol agents during the early stages of disease progression.