Potato spindle tuber viroid

The causal agent of this disease is the Potato spindle tuber viroid (PSTVd). Unlike traditional viruses, this pathogen is a small, single-stranded, circular RNA molecule that lacks a protein capsid. Once inside the plant host, it replicates and spreads systemically, causing significant physiological and morphological disruptions.

While potatoes are the primary economic host, this viroid also affects other members of the Solanaceae family, including tomatoes, peppers, and eggplants. The wide host range allows the pathogen to persist in agricultural environments, often complicating rotation and containment strategies for commercial farming operations.

Infected tubers exhibit characteristic symptoms: they become elongated, cylindrical, or spindle-shaped, often showing deep, prominent eyes and a rough, corky skin. The foliage of infected potato plants is usually stunted, with smaller, upright leaflets and shortened internodes, giving the plant a rigid and narrow appearance.

The spread of the viroid is primarily mechanical. It is easily transmitted via contaminated tools, farm machinery, and physical contact between plants. Furthermore, it can be spread through true potato seeds, pollen, and infected seed tubers, which makes the pathogen highly efficient at colonizing new fields and greenhouse batches.

Effective management relies heavily on prevention, as there is no chemical cure for viroid infections. Key strategies include:

• sourcing high-quality, certified pathogen-free seed tubers;
• strictly sanitizing equipment with appropriate disinfectants after every contact with plants;
• implementing rigorous rogueing of symptomatic plants;
• frequent monitoring of crop health to prevent local outbreaks.