Cabbage olpidium

Cabbage olpidium (Olpidium brassicae) is an obligate intracellular parasite classified within the kingdom Protista, phylum Chytridiomycota. This microscopic pathogen is widely recognized in agronomy as a significant agent affecting the roots of various vegetable crops, particularly during the early seedling stage.

The primary symptom caused by this pathogen is known as damping-off or black leg. It targets the roots and hypocotyls of cruciferous vegetables, lettuce, and certain other plants. Once infected, the plant tissues soften and turn dark, leading to structural collapse and the death of the seedling shortly after emergence.

The biological life cycle of Olpidium brassicae involves the production of motile zoospores that utilize flagella to navigate through soil moisture. Upon encountering a suitable host, the zoospores encyst on the root surface, penetrate the epidermal cells, and develop into sporangia. Under unfavorable environmental conditions, the pathogen produces resting spores that remain dormant in the soil for several years.

Disease progression is highly dependent on environmental factors, specifically high moisture levels and poor soil aeration. The pathogen thrives at temperatures ranging from 15°C to 20°C. Spread usually occurs through contaminated soil, non-sterilized growing media, agricultural tools, and irrigation water containing active zoospores.

The economic damage caused by Olpidium brassicae is significant, particularly in greenhouse operations, where it can cause mass seedling failure. Furthermore, it serves as a vector for various plant viruses, such as lettuce necrosis virus. Control strategies focus on strict sanitation and preventive practices:

• Heat sterilization or chemical treatment of nursery soil and substrates.
• Maintaining optimal drainage and avoiding over-irrigation.
• Disinfecting greenhouse tools, benches, and propagation containers.
• Implementing rigorous crop rotation and selecting high-quality seeds.