|
Type Species |
(CCCVd) |
The smallest form is a circular ssRNA of 246-247 bases as a consequence of a cytosine duplication at nucleotide 198. The most stable secondary structure is a rod-like or quasi-rod-like conformation with five domains, a central conserved region (CCR) similar to that of pospi- and hostuviroids, and a terminal conserved hairpin (TCH) (Fig. 2). The TR domain is variable as a result of 41, 50, or 55 bases being reiterated to generate forms which are between 287 and 301 bases. As the disease progresses from the early to the medium stages the small forms are modified to the large ones which also have single or double cytosine residues. Replication most probably occurs through an asymmetric rolling-circle model by analogy with PSTVd (Fig. 3). At the subnuclear level, it is mostly concentrated in the nucleolus with the remainder distributed throughout the nucleoplasm. Host range restricted to members of the Palmae family and geographic distribution to Philippines and some parts of Micronesia.
List of Species Demarcation Criteria in the Genus
An arbitrary level of less than 90% sequence similarity and distinct biological properties, particularly host range, currently separates species within genera.
Official viroid species names are in italics. Tentative names, alternative names ( ), or strains are not italicized. Viroid names, CMI/AAB description numbers ( ), genomic accession numbers of typical sequence variants [ ], sizes {b}, and assigned abbreviations ( ) are:
|
Citrus IV viroid |
[X14638] |
{284} |
(CVd-IV) |
|
Coconut cadang-cadang viroid (287) |
[J02049] |
{246-247, 287-301} |
(CCCVd) |
|
Coconut tinangaja viroid |
[M20731] |
{254} |
(CTiVd) |
|
Hop latent viroid |
[X07397] |
{256} |
(HpLVd) |
Tentative Species in the Genus
None reported.
|
| |