Viroids


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Viroids

The smallest known agents of infectious disease. Conventional viruses are made up of nucleic acid encapsulated in protein (capsid), whereas viroids are uniquely characterized by the absence of a capsid. In spite of their small size, viroid ribonucleic acids (RNAs) can replicate and produce characteristic disease syndromes when introduced into cells. Viroids thus far identified are associated with plants.

Nine different viroids have been described from widely separated geographical locations and from an assortment of herbaceous and woody plants. Viroid infections in some plant species produce profound disease symptoms ranging from stunting and leaf epinasty to plant death, whereas infections in other species produce few detectable symptoms compared to uninoculated control plants. Viroids generally have a restricted host range, although several viroids can infect the same hosts and cause similar symptoms in these hosts. Good controls are not available for diseases caused by these small infectious agents other than indexing procedures to provide viroid-free propagules. See Plant viruses and viroids, Virus

References in periodicals archive ?
3-5) There was an increase in free RNA indicating self replicating RNA viroids and free DNA indicating generation of viroid complementary DNA strands by archaeal reverse transcriptase activity.
Viroids resemble viruses, but consist of only small RNA molecules that do not have the protein coat found on viruses and that do not encode any proteins.
According to Gail Dinter-Gottlieb, there is a striking similarity in the nucleic acid sequences, and possibly in the structures, of viroids and a certain class of introns.
Dot blot hybridization assays have been used widely to detect AMV and other viruses and viroids in infected plants (Peiro et al.
The loss, removal or damage of traditional plant labels at any stage of production can result in a mother plant that has no known history, which is especially problematic because of the many viruses, viroids, phytoplasmas and other systemic pathogens that can infect propagative material.
Actinides like rutile as well as organisms like phytoplasmas and viroids have been implicated in the etiology of EMF [1,2,3,4].
In the first volume, Studies in Viral Ecology: Microbial and Botanical Host Systems, the 12 chapters define viral ecology and the basic biology of viruses, viral taxonomy, and morphology, replication, assembly, and evolutionary ecology, then viruses with microbial and plant hosting species, including bacteriophage and viral ecology as viewed through nucleic acid sequence data; viruses of cyanobacteria, eukaryotic algae, and seaweeds; the ecology and evolution of fungal, prion, and plant viruses, including geminiviruses; and viroids and viroid diseases of plants.
The enzymes may be expressed constitutively at low levels but are dramatically enhanced by numerous abiotic agents (ethylene, salicylic acid, salt solutions, ozone, UV light) and by biotic factors (fungi, bacteria, viruses, viroids, fungal cell wall components, and oligosaccharides).
Eggplant latent viroid, the candidate type species for a new genus within the Avsunviroidae family (hammmer head viroids).
Prions do not contain DNA or RNA as do fungi, bacteria, viruses, viroids, or any other previously known infectious entities.
A list of proposed standard acronyms for plant viruses and viroids.
In my opinion, concerns about latent viruses, viroids, graft incompatibility, rootstock adaptability, and plant material quality have been masking the presence of black goo disease for some years.