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[1] Tomato yellow leaf curl virus - Netherlands: first report

Date: Fri 12 Oct 2007
Source: Netherlands Plant Protection Service [edited]
<http://www.minlnv.nl/cdlpub/servlet/CDLServlet?p_file_id=22143>

Tomato yellow leaf curl virus (TYLCV) on tomato plants

This report concerns the 1st official findings of TYLCV recorded in the Netherlands. TYLCV is listed as a harmful organism for the European Community, which is known to occur in the Community and specifically regulated on tomato plants intended for planting, other than seeds. The outbreak was 1st suspected at one company in the beginning of September [2007] and officially identified at the end of September [2007]. Currently, findings concern a small number of companies and a very low number of infected plants (varying between 3 and approximately 20 plants per company). Thus far, no findings have been recorded at companies producing plantlets intended for sale to professional growers. The source of the outbreak has not been identified. A nationwide specific surveillance has been planned to determine the extent of the outbreak.

Detection has been carried out using polymerase chain reaction (PCR) tests for begomoviruses. The virus was identified as TYLCV by analysis of the PCR products. Measures at companies are ongoing in the Netherlands, whereby affected plants are removed and destroyed.
Furthermore, relevant companies have to apply insecticide treatments aimed at eradicating populations of _B. tabaci_. A hygienic protocol is required at affected companies for preventing further spread.
Trace-back has been initiated for determining the possible source of the outbreak.

[2] Tomato yellow leaf curl Thailand virus - Taiwan: first report

Date: October 2007
Source: The American Phytopathological Society, Plant Disease 2007;
91(10): 1363 [edited]
<http://www.apsnet.org/pd/searchnotes/2007/PDIS-91-10-1363A.asp>

[Reference: FJ Jan et al: First report of _Tomato yellow leaf curl Thailand virus_ in Taiwan. Plant Dis 2007, 91(10): 1363; DOI: 10.1094/PDIS-91-10-1363A]

First report of Tomato yellow leaf curl Thailand virus (TYLCTHV) in Taiwan

During the 2006 winter and 2007 spring seasons, tomato lines carrying the Ty2 gene, which confers resistance to the _Tomato leaf curl Taiwan virus_ showed severe yellowing, leaf curl, and stunting symptoms in several locations in Tainan County, Taiwan. Whiteflies were found to be associated with symptomatic plants, and disease
incidences of almost 100 percent were observed. The presence of a new resistance breaking begomovirus was suspected.

A total of 6 symptomatic leaf samples of 3 different tomato plants from each infected field were collected in Liouying (LY3, 7, and 8) and Sigang (SG9, 13, and 18) townships in Tainan County. Viral DNAs were extracted and begomoviral DNA-A was detected in all tested samples, which was 2744 base pairs for both the Liouying and Sigang isolates. On the basis of their 99.5 percent nucleotide identity, they are considered isolates of the same species.

The 2 isolates had the highest nucleotide identity (more than 98.4 percent) with the DNA-A of the _Tomato yellow leaf curl Thailand virus_ (TYLCTHV). All samples, except the LY3, were also found to be infected with _Tomato leaf curl Taiwan virus_ (ToLCTWV).

A pure TYLCTHV isolate of LY3 was obtained in _Lycopersicum esculentum_ [tomato] TK70 by transmission with _Bemisia tabaci_ biotype B. The isolated TYLCTHV was found to infect _L. esculentum_ H24 (resistant to ToLCTWV) and induce typical yellow leaf curl symptoms. To our knowledge, this is the 1st report of the presence of TYLCTHV in Taiwan.

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

[TYLCV (genus _Begomovirus_, family, _Geminiviridae_) originates from the Middle East and is one of the most damaging viruses of tomato (current name _Solanum lycopersicum_, see link below for previous names and synonyms) worldwide. It can also affect a number of other solanaceous and leguminous hosts. Infection of tomato causes plants to be stunted with small chlorotic puckered leaves. Yield losses of up to 80 percent have been reported, and field cropping of tomatoes has been abandoned in some areas due to TYLCV. The virus is
transmitted by the whitefly vector _Bemisia tabaci_ in a persistent manner. It can also be transmitted by mechanical inoculation (poorly) and by grafting, but is not transmitted by contact between plants. Disease management relies on control of the vector but may cause problems of chemical residues on the fruit. Tomato cultivars with increased resistance are available. Transgenic tomato plants incorporating TYLCV capsid protein genes have been found to be resistant to the virus.

A number of related begomoviruses exist in the tomato yellow leaf curl and tomato leaf curl disease complexes, including _Tomato yellow leaf curl Thailand virus_ and _Tomato leaf curl Taiwan virus_. These were isolated from different areas and sources and were first thought to be strains of TYLCV. However, they are now considered separate species.

Whiteflies are widely distributed and have a very wide host range of more than 600 plant species. Weed species can serve as reservoirs making control difficult. The insects cause serious crop damage not only by direct feeding, but also through transmission of viruses. They have been reported to transmit over 100 virus species, including
many begomoviruses. _B. tabaci_ is believed to be a species complex with a number of recognised biotypes varying in their distribution and vector activities.

Both TYLCV and its whitefly vector are included on the quarantine list of the European Plant Protection Organisation (EPPO).

Maps
Netherlands:
<http://worldatlas.com/webimage/countrys/europe/lgcolor/nlcolor.htm> and
<http://healthmap.org/promed?v=52.2,5.6,6>
Taiwan:
<http://www.lib.utexas.edu/maps/middle_east_and_asia/taiwan_pol92.jpg>
Tainan County via:
<http://eng.taiwan.net.tw/lan/Cht/map/index.asp#>
Map of TYLCV worldwide distribution (September 06):
<http://www.eppo.org/QUARANTINE/virus/TYLC_virus/TYLCV00_map.htm>

Pictures
TYLCV symptoms on tomato plants:
<http://www.avrdc.org/LC/tomato/tylcv05big.jpg>,
<http://www2.dpi.qld.gov.au/images/13644.jpg>  and
<http://www.eppo.org/QUARANTINE/virus/TYLC_virus/TYLCV0_images.htm>
_Begomovirus_ particles, electron micrograph:
<http://www.ncbi.nlm.nih.gov/ICTVdb/WIntkey/Images/gemini1.jpg>
_B. tabaci_ picture gallery:
<http://www.eppo.org/QUARANTINE/insects/Bemisia_tabaci/BEMITA_images.htm>

Links
TYLCV information:
<http://www.defra.gov.uk/planth/pestpics/qic2004/QIC55.pdf>  and
<http://www2.dpi.qld.gov.au/health/4250.html>
EPPO data sheet TYLCV:
<http://www.eppo.org/QUARANTINE/virus/TYLC_virus/TYLCV0_ds.pdf>
TYLCV taxonomy:
<http://www.ncbi.nlm.nih.gov/ICTVdb/ICTVdB/00.029.0.03.043.htm>
List of viruses in tomato yellow leaf curl and leaf curl complexes:
<http://www.ncbi.nlm.nih.gov/ICTVdb/Ictv/vn_indxT.htm>
_B. tabaci_ taxonomy and biotypes:
<http://www.issg.org/database/species/ecology.asp?fr=1&si=106>
EPPO data sheet _B. tabaci_:
<http://www.eppo.org/QUARANTINE/insects/Bemisia_tabaci/BEMITA_ds.pdf>
EPPO A2 list:
<http://www.eppo.org/QUARANTINE/listA2.htm>
Scientific name of tomato:
<http://www.plantnames.unimelb.edu.au/Sorting/Lycopersicon.html>. - Mod.DHA]

[see also in the archive:
Tomato yellow leaf curl virus - USA (California, Texas) 20070413.1228
Yellow leaf curl, tomato - USA (AZ): 1st report 20070226.0694
2006
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Begomovirus - multicountry: 1st reports 20060611.1625
Yellow leaf curl, tomato - Australia (QLD): 1st rep 20060330.0967
Yellow leaf curl, tomato - Multicountry: 1st reports 20060304.0702
2001
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Tomato yellow leaf curl virus species 20010622.1187
1998
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Tomato yellow leaf curl begomovirus: spreading 19980528.1026
1997
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Tomato yellow leaf curl virus and citrus canker - USA (Florida) 19970903.1869]
 

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