Potato spindle tuber viroid
| Potato spindle tuber viroid | |
|---|---|
| Virus classification | |
| Group: | Viroids |
| Family: | Pospiviroidae |
| Genus: | Pospiviroid |
| Species: | Potato spindle tuber viroid |
The Potato spindle tuber viroid ("PSTVd") was the first viroid to be identified.[1][2][3][4] PSTVd is a small, circular RNA molecule closely related to the chrysanthemum stunt viroid. Present within the viroidal RNA is the Pospiviroid RY motif stem loop. The natural hosts are potatoes (Solanum tuberosum) and tomatoes (Solanum lycopersicum). All potatoes and tomatoes are susceptible to PSTVd and there is no form of natural resistance. Natural infections have also been seen in avocados and infections in other solanaceous crops have been induced in the laboratory.
Strains and their symptoms
Different strains of PSTVd exist and symptoms range from mild to severe. Mild strains produce no obvious symptoms. Symptoms in severe strains are dependent on environmental conditions and are most severe in hot conditions. Symptoms may be mild in initial infections but become progressively worse in the following generations. Common symptoms of severe infections include colour changes in the foliage, smaller leaves and spindle like elongation. Sprouting also occurs at a slower rate than in unaffected potatoes. Infected tomatoes are slower to show symptoms which include stunted growth with a ‘bunchy top’ caused by shortened internodes. Leaves become yellow or purple and often become curled and twisted. Necrosis eventually occurs in the veins of the bottom and middle leaves and the top leaves don’t die but are reduced in size. Fruit ripening is also affected leading to hard, small, dark green tomatoes.
Long distance spread of PSTVd usually occurs via infected seeds but transmission via aphids (Myzus persicae) also occurs but only in the presence of PLRV (potato leaf roll virus). Mechanical transmission also occurs once it has been introduced to an area.
Primary and secondary structure of PSTVd
PSTVd comprises 359 nucleotides.
| Primary Structure |
1 CGGAACUAAA CUCGUGGUUC CUGUGGUUCA CACCUGACCU CCUGAGCAGA AAAGAAAAAA 61 GAAGGCGGCU CGGAGGAGCG CUUCAGGGAU CCCCGGGGAA ACCUGGAGCG AACUGGCAAA 121 AAAGGACGGU GGGGAGUGCC CAGCGGCCGA CAGGAGUAAU UCCCGCCGAA ACAGGGUUUU 181 CACCCUUCCU UUCUUCGGGU GUCCUUCCUC GCGCCCGCAG GACCACCCCU CGCCCCCUUU 241 GCGCUGUCGC UUCGGCUACU ACCCGGUGGA AACAACUGAA GCUCCCGAGA ACCGCUUUUU 301 CUCUAUCUUA CUUGCUUCGG GGCGAGGGUG UUUAGCCCUU GGAACCGCAG UUGGUUCCU |
| Secondary Structure |
 Putative secondary structure of the PSTVd viroid |
The nucleotides that are highlighted are found in most other viroids.
References
- ↑ Diener TO (August 1971). "Potato spindle tuber "virus". IV. A replicating, low molecular weight RNA". Virology. 45 (2): 411–28. PMID 5095900. doi:10.1016/0042-6822(71)90342-4.
- ↑ "ARS Research Timeline - Tracking the Elusive Viroid". 2006-03-02. Retrieved 2007-07-18.
- ↑ Discovery of Viroids
- ↑ Zimmer, Carl (September 25, 2014). "A Tiny Emissary From the Ancient Past". New York Times. Retrieved September 26, 2014.
Bibliography
- Agrois, George N., 1936- Plant pathology (3rd edition) San Diego: Academic Press, 1988.
- Singh, R.P; Fletcher J.D. ; "Background of disease (potato spindle tuber) and method of control", Agriculture and Agri food Canada, Crop & Food Research New Zealand Retrieved November 15, 2007
- DEFRA Plant Health
- "Pathogen and plant damage (potato spindle tuber)" Retrieved November 15, 2007, from George N. Agrois, Plant Pathology (3rd Ed) San Diego: Academic Press,(1988).