A ProMED-mail post <http://www.promedmail.org>
ProMED-mail is a program of the International Society for Infectious Diseases <http://www.isid.org>
Date: Fri 17 Apr 2020
Source: Ausveg [edited]
<https://ausveg.com.au/articles/tomato-spotted-wilt-virus-a-very-sporadic-but-destructive-potato-disease-2/>
A project was undertaken to determine the drivers behind epidemics of _Tomato spotted wilt virus_ (TSWV) in potato crops. While major epidemics in potato are rare, when they do occur - as during the late 1990s and early 2000s in parts of southern Australia - significant losses will occur. TSWV infection in tubers can lead to internal blackening and necrosis. Often the symptoms may not be obvious from the outside of the tuber.
Major outbreaks in the late 1990s coincided with the first detection of western flower thrips [WFT] in Australia. Calum Wilson, University of Tasmania, said, "There was concern that there was some link between that arrival and the subsequent increase in TSWV epidemics in potato.
The WFT is generally regarded as the most efficient vector of TSWV globally."
The researchers discovered that onion thrips in Tasmania and both onion and tomato thrips in mainland sites were the only TSWV vectors associated with southern Australian potato crops. WFT were never found. Subsequent testing showed that onion and tomato thrips are as efficient at transmitting TSWV as WFT. "There was no association between thrips numbers and TSWV infection levels," Professor Wilson said.
Surveys of weeds and other possible alternate plant hosts of TSWV revealed that inoculum sources varied depending on location. "In South Australia, the suspicion was that the major inoculum sources were much further away; perhaps from an infected crop that was never identified.
In Tasmania, we tended to get more localised infections, which suggested that plants immediately surrounding the crops were the source. Understanding the source was important for control."
Variety screening trials were established. Crops were regularly monitored to record the initial infection levels, which may have come from infected seed, and subsequent spread of the virus. No potato variety was immune or highly resistant to infection, although some appear to be less prone to tuber infection and blackening.
Preliminary testing of foliar and preplant insecticide treatments suggested they offer limited value for disease control. As TSWV is very unpredictable in potato, growers are restricted in the ways to limit the impact. The project raised awareness of TSWV as an issue for the potato industry, which prompted the virus to be considered for seed potato certification.
--
Communicated by: ProMED-mail <promed@promedmail.org>
[Tomato spotted wilt virus (TSWV; type species of genus _Orthotospovirus_, previously _Tospovirus_) has one of the broadest host ranges among plant viruses and is one of few affecting both dicot and monocot hosts. It is regarded as one of the most economically destructive plant pathogens and has had a serious impact on many crop species worldwide causing up to 100 percent yield loss in some instances. Symptoms on potato may include necrotic areas and distortions on leaves and severe stunting of plants; tubers may be small and distorted with necrotic spots and black necrotic centres.
Infected tubers may also be asymptomatic but will give rise to severely affected plants when used as seed tubers.
TSWV is transmitted by various species of thrips, including the western flower thrips (_Frankliniella occidentalis_), the onion thrips (_Thrips tabaci_) and the tomato thrips (F. schultzei) mentioned above. Thrips are plant pests in their own right causing considerable leaf damage. The virus is not seed transmitted but transmission by mechanical means and grafting has been reported. Weed species can serve as pathogen reservoirs. Disease management may include vector control, use of clean planting material, control of weed hosts of virus and vectors, as well as phytosanitary measures. Breeding programmes for resistant varieties have been established for some crops, including potato, but resistance breaking strains of TSWV have been reported, for example in capsicum and tomato cultivars (e.g.
ProMED-mail post http://promedmail.org/post/20080123.0280).
Due to their agricultural importance, research on tospoviruses has increased dramatically in recent years. As a result, many new species are being found and many more can be expected to exist.
Maps
Australia (with states):
<https://www.interkart.de/media/catalog/product/p/o/pod10th103_103_australia_physical.jpg>
Pictures
TSWV symptoms on potato:
<https://bugwoodcloud.org/images/768x512/1578136.jpg>,
<https://c8.alamy.com/comp/A55ABA/tomato-spotted-wilt-virus-symptoms-on-potato-leaves-A55ABA.jpg>,
<https://nwdistrict.ifas.ufl.edu/phag/files/2013/06/tomato-wilted-virus.jpg>,
<https://ephytia.inra.fr/en/I/30297/TSWV5> and <https://www.researchgate.net/profile/Gerald_Holmes2/publication/226915501/figure/fig1/AS:393680235057156@1470872090520/Symptoms-of-Tomato-spotted-wilt-virus-on-potato-leaves-A-C-and-D-s-t-e-m-s-B-and.png>
TSWV on a range of hosts:
<http://garden.org/pics/2014-01-14/farmerdill/6f17df.jpg> (tomato
fruit)
<http://www.tomatonews.com/maj/phototheque/photos/Images_TN/6239_00.jpg>,
<https://bugwoodcloud.org/images/768x512/1573188.jpg> (capsicum leaf), <http://www.hort.cornell.edu/livegpath/images/pepper_tswv5x1200.jpg>
(capsicum fruit),
<http://vegetablemdonline.ppath.cornell.edu/PhotoPages/Tomatoes/Tom_SpWilt/Tom_SpWiltPhotoList.htm>
and
<http://www.forestryimages.org/browse/TaxImages.cfm?Area=62&fam=652&genus=Tospovirus>
TSWV particles, electron microscopy:
<https://ephytia.inra.fr/en/Images/view/18124>
Western flower thrips:
<http://www.insectimages.org/images/768x512/4387048.jpg>
Links
TSWV in potato:
<http://agriculture.vic.gov.au/agriculture/pests-diseases-and-weeds/plant-diseases/vegetable/potato-diseases/tomato-spotted-wilt-virus-in-potatoes>,
<http://blogs.cornell.edu/livegpath/gallery/potatoes/tomato-spotted-wilt-virus-tswv/>
(with pictures),
<https://pnwhandbooks.org/plantdisease/host-disease/potato-solanum-tuberosum-tomato-spotted-wilt>,
<http://frenchseedpotato.com/index/tomato-spotted-wilt-virus> and <https://link.springer.com/article/10.1007/s12230-013-9337-9>
(research on cultivar resistance)
Information on TSWV and tospoviruses:
<http://www.dpvweb.net/dpv/showdpv.php?dpvno=412>,
<https://aces.nmsu.edu/pubs/_h/H242/welcome.html>,
<http://www.ipm.ucdavis.edu/PMG/r783102211.html>,
<http://vegetablemdonline.ppath.cornell.edu/factsheets/Virus_SpottedWilt.htm>
and
<https://www.daf.qld.gov.au/__data/assets/pdf_file/0007/58777/Thrip-viruses-veg-crops.pdf>
Review on tospoviruses, impact and global crop risks:
<https://www.annualreviews.org/doi/full/10.1146/annurev-virology-100114-055036>
Virus taxonomy via:
<https://talk.ictvonline.org/taxonomy/>
Thrips information:
<https://projects.ncsu.edu/cals/course/ent425/library/compendium/thysanoptera.html>,
<http://www.cals.ncsu.edu/course/ent425/text18/plantvectors.html> and <https://www2.ipm.ucanr.edu/agriculture/onion-and-garlic/thrips/>
- Mod.DHA
HealthMap/ProMED map available at:
Australia: <http://healthmap.org/promed/p/186>]
[See Also:
2019
----
Impatiens necrotic spot virus, capsicum - USA: (MA)
http://promedmail.org/post/20190611.6514103
2018
----
Cucumber mosaic & tomato spotted wilt viruses, capsicum - Europe:
(Balkan region) http://promedmail.org/post/20180914.6028544
2015
----
Vegetable viruses - Spain: (AN) alert
http://promedmail.org/post/20151204.3839034
2014
----
Multiple viruses, capsicum - USA: (CA)
http://promedmail.org/post/20140901.2738894
2010
---
Tospovirus complex, tomato - Brazil
http://promedmail.org/post/20100719.2419
2008
---
Tomato spotted wilt virus, capsicum - Spain (Almeria)
http://promedmail.org/post/20080123.0280
2007
---
Tomato viruses TSWV, TICV - Jordan: 1st reports
http://promedmail.org/post/20071223.4123
Tomato spotted wilt virus, tomato - USA (CA)
http://promedmail.org/post/20070608.1872
and additional items on tospoviruses in the archives]
Topics
Species
