Potato streptomycosis

The disease is caused by the soil-dwelling bacterium Streptomyces bottropensis, which belongs to the actinomycetes group. This organism functions as a pathogen that primarily targets the underground parts of plants. It is highly persistent in the soil environment, where it can survive for many years by utilizing organic matter, waiting for a suitable host crop to initiate a parasitic infection.

Potatoes are the primary crop affected by this pathogen, although it can also impact other root vegetables. The bacteria invade the tubers during the early stages of development, typically entering through lenticels or minor mechanical wounds on the skin. The spread of the disease is predominantly linked to contaminated soil, movement of machinery between fields, and the use of infected seed tubers.

Clinical signs of the infection include various forms of scab, ranging from superficial scaly lesions to deeper, corky pitted spots on the tuber surface. These lesions are typically brown or dark in color and significantly disrupt the tuber's epidermis. The presence of these lesions negatively impacts the marketability of the crop and creates entry points for secondary pathogens like fungi and other bacteria.

Environmental conditions play a critical role in the severity of the outbreak. Streptomyces bottropensis thrives in warm, dry soil conditions, particularly when the soil pH is neutral or slightly alkaline. Unlike many other bacterial diseases that prefer acidic environments, this specific pathogen becomes significantly more aggressive when the soil is limed or naturally alkaline, making soil management a key aspect of prevention.

• Use of crop rotation to break the infection cycle.
• Selection of scab-resistant potato varieties.
• Maintenance of soil pH levels within an acidic range.
• Seed tuber disinfection with appropriate bactericides.
• Optimal irrigation during the tuber initiation stage.

The economic impact of this disease is primarily related to reduced crop quality and post-harvest storage losses. Since the damaged skin layers are highly susceptible to moisture loss and decay, infected batches of potatoes have a much shorter shelf life. Integrated pest management, focusing on soil structure and cultivar selection, is essential for minimizing losses caused by this actinomycete.