viroid

viroid microscopic infectious agent, much smaller than a virus , that infects higher plants such as potatoes, tomatoes, chrysanthemums, and cucumbers, causing stunted or distorted growth and sometimes death. It can be transmitted by pollen, seed, or farm implements. Viroids are single strands of RNA and lack the protein coat of viruses. They do not code for any specific protein but are able to replicate themselves in the nuclei of infected cells. Some scientists believe viroids are parts of normal RNA that have gone awry. Potato spindle tuber viroid was the first to be identified.

viroid A piece of infectious nucleic acid. Viroids appear to resemble viruses in some respects, but consist only of small. closed circles of RNA: there is no capsid. They can cause disease in plants (e.g. potato spindle tuber disease and hop stunt).