Tiny particle known to cause some plant diseases and suspected of causing some human diseases. It is much smaller than a virus and consists of a short ribonucleic acid (RNA) chain and no protective protein coat.
A small, naked, infectious molecule of RNA. Viroids differ from viruses by the absence of a dormant phase and by genomes that are much smaller than those of known viruses.
A pathogenic entity, formerly presumed to be a virus, is now identified as a low molecular weight ribonucleic acid, not a ribonucleo-protein. T.O. Diener first introduced the term in 1972 in his research on potato spindle tuber “virus.” Similar agents may cause citrus exocortis and chrysanthemum stunt diseases.