PLMVd

Potato leaf mosaic viroid (PLMVd) is a plant viroid that infects potato and other solanaceous plants. It is a small, circular RNA molecule, typically about 330 to 360 nucleotides in length, that lacks protein-coding capacity and relies on host enzymes for replication and movement within the plant. PLMVd is classified within the Avsunviroidae, a group of chloroplast-replicating viroids. It replicates in chloroplasts via a rolling-circle mechanism and contains hammerhead ribozymes that aid in processing replicative RNAs into mature genome units.

Infected plants may exhibit leaf mosaic patterns, chlorotic mottling, leaf distortion or curling, and reduced vigor or yield. The severity of symptoms varies with the viroid isolate, the plant cultivar, and environmental conditions. The viroid can be present in tubers and spread to new plants through vegetative propagation, as well as via mechanical transmission. Seed transmission is considered rare.

Diagnosis is typically based on molecular assays such as RT-PCR and Northern blot hybridization, with sequence analysis used for confirmation. Management aims to prevent introduction into clean propagation material and to eliminate the viroid from infected stock. Approaches include the use of certified disease-free seed and seed potatoes, meristem tip culture combined with thermotherapy, and strict sanitation to prevent mechanical spread.

PLMVd has a global distribution and is subject to quarantine and regulatory scrutiny in some potato-producing regions. It is one of several viroids that affect solanaceous crops and is studied for its interactions with host plants and implications for crop health and production safety.