CSVd

Chrysanthemum stunt viroid (CSVd) is a plant pathogen in the viroid category. Viroids are small, circular, single-stranded RNA molecules that infect plants and do not encode proteins. CSVd's genome is about 359 nucleotides in length and replicates in the plant cell nucleus using host enzymes through a rolling-circle mechanism. It mainly infects chrysanthemums and can also infect a limited range of other ornamental plants in the Asteraceae family. Symptoms are variable and depend on cultivar and environmental conditions.

Symptoms of CSVd infection include stunted growth, distorted and cupped leaves, poor flowering, flower deformities, and overall reduced vigor. Some infections may be mild or asymptomatic in certain hosts, complicating detection in the field.

CSVd is transmitted primarily through vegetative propagation and grafting of infected plant material. It can spread via contaminated tools and handling during propagation or pruning. Seed transmission is considered rare or uncertain, and there are no well-established natural insect vectors.

Diagnosis relies on molecular methods such as reverse transcription PCR (RT-PCR) and quantitative RT-PCR, as well as nucleic acid hybridization and sequencing for confirmation. Serological assays are not applicable to viroids since they lack a coat protein.

Management focuses on prevention and sanitation. Use certified virus-free propagation material, implement quarantine procedures, and regularly test stock. Remove and destroy infected plants and sanitize tools between plants. Crop rotation or avoiding replanting in the same facility can help reduce risk, though disinfection alone cannot eliminate the pathogen from an affected greenhouse.