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October 2, 2007
Source: The American Phytopathological Society, Plant Disease 2007; 91(8): 1055 [edited]
<http://apsjournals.apsnet.org/doi/abs/10.1094/PDIS-91-8-1055A>

[Reference: J Th J Verhoeven et al: First report of _Potato spindle tuber viroid_ in tomato in Belgium. Plant Dis; 91(8): 1055; DOI: 10.1094/PDIS-91-8-1055A]

First report of Potato spindle tuber viroid in tomato in Belgium

During August 2006, a sample of a tomato plant (_Solanum lycopersicum_, formerly _Lycopersicum esculentum_) from a greenhouse in Belgium was received for diagnosis. The plant showed severe growth reduction and the young leaves were chlorotic and distorted. In the greenhouse, the disease had been spreading slowly along the row.

These observations suggested the presence of a viroid infection, and reverse transcriptase (RT)-PCR [polymerase chain reaction] for pospiviroids yielded a positive result (amplicons of approximately 196 and 360 base pairs). Sequence analysis of the larger amplicon [PCR product] revealed that the genome was 358 nucleotides and 100
percent identical to 2 previously published isolates of _Potato spindle tuber viroid_ (PSTVd) from the United Kingdom and Australia. A pathogen associated with the symptomatic tomato plants was therefore identified as PSTVd.

Tracing the origin of the infection revealed the following information: during November 2005, 8-day-old tomato seedlings raised from seed by a Dutch nursery were transferred to a small part of the greenhouse of the Belgian grower; 7 to 8 weeks later, the plants were transplanted to their final destination; during May 2006, the grower
first observed growth reduction in a single plant; several weeks later, similar symptoms were observed in 2 more plants in the same row close to the 1st symptomatic plant; and by September [2006], there were approximately 20 symptomatic tomato plants, all located in 2 adjacent rows.

The viroid outbreak was fully eradicated by destroying all tomato plants in the affected rows as well as in 2 adjacent rows at both sides. The absence of further infections was confirmed by testing approximately 1200 tomato plants in pooled samples for PSTVd by RT-PCR (2) and real-time RT-PCR (1). The origin and the method of introduction and spread of the viroid remain unclear.

References:
1. N. Boonham et al. J. Virol. Methods 116: 139, 2004.
2. R. A. Mumford et al. Plant Pathol. 53: 242, 2004.
3. J. Th. J. Verhoeven et al. Eur. J. Plant Pathol. 110: 823, 2004.

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

[_Potato spindle tuber viroid_ (PSTVd; type member of genus _Pospiviroid_) is an important pathogen of solanaceous crops, causing the diseases 'spindle tuber' in potato and 'bunchy top' in tomato. Yield losses can be up to 65 percent in potato and as much as 50 percent in tomato. Symptoms in tomatoes include stunting, leaf
chlorosis and distortion, and shortening of internodes. All varieties of tomato and potato appear to be susceptible, with no natural resistance to PSTVd available in either host. Other solanaceous crop and weed species are also susceptible to PSTVd.

Spread occurs via infected plants or plant parts, seed, pollen, mechanical means, or plant-to-plant contact. Only in the presence of _Potato leafroll virus_ (PLRV; genus _Polerovirus_), PSTVd can also be transmitted by an aphid vector (_Myzus persicae_). PSTVd (like viroids in general) is exceptionally stable due to its molecular structure and can survive in sap or leaf litter for considerable time.

PSTVd has been found in many countries around the world, including parts of North and South America, Asia, and Oceania. The pathogen is not endemic to Western Europe, but in recent years outbreaks have been reported in France, UK, Germany, and the Netherlands. In addition, the disease is established in Eastern Europe, including for
example Poland and Russia. The European Plant Protection Organisation (EPPO) has therefore listed PSTVd as an A2 quarantine pathogen.

Maps
Belgium:
<http://worldatlas.com/webimage/countrys/europe/lgcolor/becolor.htm>
Europe:
<http://worldatlas.com/webimage/countrys/eu.htm>
Worldwide distribution of PSTVd (September 2006):
<http://www.eppo.org/QUARANTINE/virus/PSTVd/PSTVD0_map.htm>

Pictures
Symptoms on tomato:
<http://www.bspp.org.uk/ndr/jan2004/2003-68-2.jpg> and
<http://www.forestryimages.org/browse/detail.cfm?imgnum=0162082>
Affected potato tubers:
<http://vegetablemdonline.ppath.cornell.edu/Images/Potatoes/PotatoViruses/PotatoVirusfs7.jpg>
Photo gallery of symptoms on potato and tomato:
<http://www.eppo.org/QUARANTINE/virus/PSTVd/PSTVD0_images.htm>

Links
Information on PSTVd:
<http://www.defra.gov.uk/planth/pestnote/pstv.htm> and
<http://www.eppo.org/QUARANTINE/virus/PSTVd/PSTVD0_ds.pdf>
Diagnosis of PSTVd:
<http://www.eppo.org/QUARANTINE/virus/PSTVd/pm7-33(1)%20PSTVD0%20web.pdf>
PSTVd taxonomy:
<http://phene.cpmc.columbia.edu/ICTVdB/80001101.htm>
PLRV taxonomy:
<http://phene.cpmc.columbia.edu/ICTVdB/39002001.htm>
EPPO A2 quarantine list:
<http://www.eppo.org/QUARANTINE/listA2.htm>. - Mod.DHA]


[see also in the archive:
Potato spindle tuber viroid, potato - Russia: novel strains 20070423.1323
2004
----
Potato spindle tuber viroid, tomato - Germany 20040630.1738
Potato spindle tuber viroid, tomato - United Kingdom 20040117.0179
2003
----
Potato spindle tuber viroid, tomato - United Kingdom 20030909.2268
Potato spindle tuber viroid, eradication - France 20030814.2021
Potato spindle tuber viroid - Canada: eradication 20030806.1928
Potato spindle tuber, tomato - Australia: eradication 20030804.1913
Potato spindle tuber, tomato - Australia (NSW) (02) 20030620.1516
Potato spindle tuber, tomato - Australia (NSW) 20030618.1506
2002
----
Potato spindle tuber viroid, potato - France 20021011.5520
2001
----
Potato spindle tuber viroid, tomatoes - Australia 20010622.1186
Potato spindle tuber viroid - New Zealand 20010314.0514
2000
----
Potato spindle tuber viroid - Costa Rica 20000221.0236
1999
----
Plant pathogens, intercepts, EPPO 19991125.2088]
 

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