Potato apical chlorosis viroid

The causative agent of this plant disease is Pospiviroid apicimpeditum, a pathogen belonging to the family Pospiviroidae. Unlike viruses, this viroid is a small, naked, circular RNA molecule that does not encode proteins but uses the host plant's enzymatic system to replicate, disrupting normal plant development.

The primary host for this pathogen is the potato plant (Solanum tuberosum). Because the viroid is systemic, it infects all plant tissues, including tubers. This makes the use of infected tubers for planting the most significant risk factor, as it perpetuates the disease in subsequent generations.

Symptoms of the infection manifest as stunted growth, apical chlorosis (yellowing of the upper leaves), and leaf deformation. Infected plants often show shortened internodes, and the resulting tubers frequently exhibit abnormal shapes, such as elongated or spindle-like forms, which significantly impacts marketability and yield quality.

The spread of the viroid occurs primarily through infected seed potatoes and mechanical transmission during field operations. Contaminated tools used for pruning, cultivation, or harvesting can easily transfer the infectious sap from diseased plants to healthy ones, facilitating rapid disease spread within a crop.

Control measures primarily rely on stringent phytosanitary practices. Since there is no chemical cure for viroid infections, management depends on using certified disease-free planting material, disinfecting all farming equipment, and implementing rigorous roguing of any plants showing symptoms to prevent further transmission throughout the fields.