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Date: August, 2007
[1] _Columnea latent viroid_ - United Kingdom: 1st report
[2] _Tomato chlorotic dwarf viroid_ - United Kingdom: 1st report

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[1] _Columnea latent viroid_ - United Kingdom: 1st report
Date: Fri 17 Aug 2007
Source: North American Plant Protection Organization, Phytosanitary Alert System [edited] <http://www.pestalert.org/viewNewsAlert.cfm?naid=47>

1st report of _Columnea latent viroid_ on tomatoes in the United Kingdom

The UK Department for Environment, Food and Rural Affairs (DEFRA) has reported 2 outbreaks of _Columnea latent viroid_ (CLVd; Pospiviroidea) in tomato production nurseries in England (DEFRA, 2007). To prevent further spread of the viroid, restrictions have been placed on the distribution and sale of the fruit and hygiene measures have been implemented at the affected nurseries. Investigations are underway to establish the origin and extent of the infection and whether there are links to other sites. CLVd is considered absent from the United Kingdom and could pose a significant risk to tomato crops.

Although the severity of viroid symptoms in tomato may vary, they can be serious, with infected plants displaying symptoms similar to _Potato spindle tuber viroid_ (PSTVd). Chlorosis, bronzing, leaf distortion, and growth reductions are possible. Potatoes are considered a natural host for CLVd however, DEFRA reports infections resulting from exposure to infected material are highly unlikely under natural growing conditions.

The most effective means of controlling viroid diseases such as CLVd is exclusion and eradication of infected materials. Viroids are easily transmitted by mechanical means and once introduced onto a production site or into a facility they can easily be spread via contaminated cutting tools, on machinery, by handling, or through direct plant-to-plant contact. While the source for these viroids in crops such as tomato is not always clearly understood, many viroids, including the closely related PSTVd, are seed transmitted, suggesting that seed transmission could have played a direct or indirect role in these recent CLVd outbreaks in the UK. In addition, it has been shown that ornamental hosts such as, _Columnea erythrophae_, _Brunfelsia undulata_ [Jamaican raintree], and _Nematanthus wettsteinii_ [goldfish plant] can be infected by CLVd asymptomatically and serve as reservoirs for the viroid.

References:
1. DEFRA, 2007. First UK findings of _Columnea latent viroid_ on tomato production nurseries. Department for Environment, Food and Rural Affairs (UK).
<http://www.defra.gov.uk/planth/newsitems/clvd.htm>
2. Hammond RW, 2003. _Columnea latent viroid_. pp. 231-231 IN A Hadidi A, Flores R, Randles JW, and Semancik JS: Viroids. CSIRO Publishing, Victoria, Australia. 370 pp.
3. Hammond RW and Owens RA, 2006. Viroids: New and Continuing Risks for Horticultural and Agricultural Crops. APSnet Feature Story, November 2006. <http://apsnet.org/online/feature/viroids/>
4. Verhoeven JThJ, Jansen CCC, Willemen TM, Kox LFF, Owens RA, and Roenhorst JW. 2004. Natural infections of tomato by _Citrus exocortis viroid_, _Columnea latent viroid_, _Potato spindle tuber viroid_, and _Tomato chlorotic dwarf viroid_. European Journal of Plant Pathology Vol. 110(8): 823-831.

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Communicated by:
J. Allan Dodds
Former ProMED-mail plant disease moderator
<dodds@ucr.edu>

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[2] _Tomato chlorotic dwarf viroid_ - United Kingdom: 1st report
Date: Fri 4 May 2007
Source: DEFRA (UK Department for Environment, Food, and Rural Affairs) [edited]
<http://www.defra.gov.uk/planth/newsitems/tcdv.htm>


1st UK finding of _Tomato chlorotic dwarf viroid_ -- implications for importers and growers of solanaceous plants

Following the identification in 2006 of _Potato spindle tuber viroid_ (PSTVd) in the UK and several other EU countries, in the ornamental species _Brugmansia_ and _Solanum jasminoides_, a survey for this harmful viroid was initiated. A 2nd closely related viroid, _Tomato chlorotic dwarf viroid_ (TCDVd) has now been identified for the 1st time in the UK by laboratory testing of imported petunias. As a result of these findings, the UK PSTVd survey will be extended to include petunia.

Like PSTVd, TCDVd causes few symptoms in ornamental hosts. Some puckering and distortion of the leaves and yellowing of the veins has been observed in infected plants, but these symptoms would seem to be temporary. However TCDVd can infect tomato crops, where it causes serious problems, with symptoms similar to those caused by PSTVd, such as stunting and yield loss. There is a strong risk that TCDVd may also infect other important solanaceous crops such as peppers. The major concern is that these infected ornamentals could act as a means for the dispersal of viroids, as its movement between ornamentals and the major hosts, by either mechanical or insect assisted transmission, cannot be ruled out. There is also a theoretical risk to potatoes from exposure to infected material, but this is extremely unlikely under normal (that is, in the field) growing conditions.

Given the recent findings, growers of all solanaceous ornamentals should consider carefully the sourcing of all their propagation material, rooted cuttings, young and mature plants. Growers are strongly advised to seek assurances from their suppliers about the status of any material ordered and to have material already received tested for viroids before further propagation. Seeds of ornamentals should also be considered a potential source until proven otherwise. However, propagation of cuttings from infected plants is considered the most likely route of infection.

Tomato and pepper growers are advised to avoid bringing solanaceous ornamental plants onto their nurseries. A helpful fact sheet on _Potato spindle tuber viroid_ is available from the Horticultural Development Council (HDC). Given their close relationship, the advice given for PSTVd will also apply for TCDVd.

As part of an official survey, samples will be collected by Defra's Plant Health and Seeds Inspectorate (PHSI) and sent for laboratory testing. PSTVd is an EU Annex IAI listed pathogen and TCDVd is absent from the EU and is considered to pose a significant risk to tomato crops; this means that any material found to be infected during the
survey will be destroyed.

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Communicated by:
ProMED-mail
<promed@promedmail.org>

[Following detection of PSTVd and the adoption of EC emergency measures in the UK, in 2007 Member States of the European Union were required to carry out a survey of host plants for the presence of PSTVd. This survey has led to these detections of CLVd and TCDVd, which are both closely related to PSTVd.

CLVd is classified in the genus _Pospiviroid_ for which the type member is PSTVd.

TCDVd was detected with a polymerase chain reaction (PCR) test specific for pospiviroids, but is yet officially unclassified to a genus. The viroid has previously been intercepted in the Netherlands in quarantined petunia material from the United States and has also been reported there in tomatoes.

Map of the UK:
<http://www.lib.utexas.edu/maps/europe/united_kingdom.gif>

Pictures
PSTVd symptoms on tomato plant:
<http://www.forestryimages.org/images/192x128/0162082.jpg>
Leaf symptoms on potato:
<http://www.omafra.gov.on.ca/english/crops/facts/98-02514.jpg>
Affected potato tubers:
<http://vegetablemdonline.ppath.cornell.edu/Images/Potatoes/PotatoViruses/PotatoVirusfs7.jpg>

Links
Publication 'First report of Tomato chlorotic dwarf viroid infecting commercial Petunia stocks in the United Kingdom'
<http://www.bspp.org.uk/ndr/july2007/2007-48.asp>
TCDVd taxonomy:
<http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Info&id=100785&lvl=3&lin=f&keep=1&srchmode=1&unlock>
CLVd taxonomy:
<http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Info&id=12901&lvl=3&lin=f&keep=1&srchmode=1&unlock>
Genus _Pospiviroid_ taxonomy and species list:
<http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Undef&id=185753&lvl=3&keep=1&srchmode=1&unlock>
PSTVd taxonomy:
<http://www.ictvdb.rothamsted.ac.uk/ICTVdB/80.001.0.01.001.htm>
Information on PSTVd infection of crops:
<http://www.defra.gov.uk/planth/pestnote/pstv.htm> and
<http://www.defra.gov.uk/planth/pestpics/qic2004/QIC68.pdf>
PSTVd information and diagnosis:
<http://www.csl.gov.uk/specialInterest/PSTVd.pdf>  and
<http://www.eppo.org/QUARANTINE/virus/PSTVd/pm7-33(1)%20PSTVD0%20web.pdf>
Viroids detected on tomato samples in the Netherlands:
<http://archives.eppo.org/EPPOReporting/2005/Rse-0505.pdf>
General information and review on viroids:
<http://www.actabp.pl/pdf/3_2004/587.pdf>
DEFRA website:
<http://www.defra.gov.uk/>
Horticultural Development Council:
<http://www.hdc.org.uk/index.asp>.  - Mod.DHA]

[see also in the archive:
2003
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Potato spindle tuber viroid, tomato - United Kingdom 20030909.2268
Potato spindle tuber, tomato - Australia (NSW) (02) 20030620.1516
Potato spindle tuber, tomato - Australia (NSW) 20030618.1506
2001
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Potato spindle tuber viroid, tomatos - Australia 20010622.1186
Potato spindle tuber viroid - New Zealand 20010314.0514]

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