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: February 2015
Source: British Society for Plant Pathology, New Disease Reports [edited] <http://www.ndrs.org.uk/article.php?id=031002>
[Ref: MA AL-Saleh et al (2015): First reports of _Lettuce big-vein associated virus_ and _Mirafiori lettuce big-vein virus_ infecting lettuce in Saudi Arabia. New Disease Reports 31, 2; DOI:
10.5197/j.2044-0588.2015.031.002]
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Lettuce (_Lactuca sativa_) is a common vegetable in Saudi Arabia, being cultivated on more than 4000 ha [about 9884 acres] either in open fields or in greenhouses. In March 2014, field lettuce crops were surveyed in the Riyadh region and around 40 percent of plants were observed to have virus-like symptoms including vein clearing, stunting, deformed leaves and thickening of the main veins. These symptoms resemble those caused by lettuce big-vein disease (LBVD), an important disease of lettuce worldwide. Both _Lettuce big-vein associated virus_ (LBVaV) and _Mirafiori lettuce big-vein virus_ (MiLBVV) are associated with LBVD.
A total of 19 samples (17 symptomatic and 2 symptomless) were collected from 4 fields and subjected to a multiplex reverse transcription (RT) PCR for the simultaneous detection of LBVaV and MiLBVV. The presence of [the fungal vector -- see comment below] was confirmed in the rootlets of all the symptomatic plants by light microscopy. 16 of the 17 samples showing symptoms were infected with LBVaV, 9 with MiLBVV and 8 with both LBVaV and MiLBVV. The 2 symptomless samples were found to be negative for both viruses.
Sequences of LBVaV had 98 percent nucleotide (100 percent amino acid [aa]) identity with a sequence from Spain and 99 percent nucleotide (100 percent aa) identity with a sequence from Japan. MiLBVV sequences showed 98 percent (99 percent aa) and 99 percent nucleotide identity (99 percent aa) with an isolate from Spain.
To our knowledge, this is the 1st report of the occurrence of LBVD-associated viruses LBVaV and MiLBVV in Saudi Arabia. Further surveys [to determine] the incidence and distribution of both LBVaV and MiLBVV in Saudi Arabia are in progress.
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Communicated by: ProMED-mail <promed@promedmail.org>
[_Lettuce big-vein associated virus_ (LBVaV; only species in genus _Varicosavirus_, unassigned to a family) and _Mirafiori lettuce big-vein virus_ (MiLBVV; genus _Ophiovirus_ with type species _Citrus psorosis virus_, family _Ophioviridae_) are transmitted between host roots by the soil inhabiting oomycete (fungus-like organism) _Pleotrachelus virulentus_ (previously _Olpidium virulentus_, earlier considered a non-crucifer affecting strain of _O. brassicae_).
Although both viruses have the same vector, they have different particle morphology and are serologically unrelated.
Lettuce big-vein disease (LBVD) can seriously reduce yield and quality of the crop. Symptoms may include distortion, thickening, and ruffling of leaves; vein clearing; enlarged veins and petioles; and stunting of plants. Affected plants often display striking symptoms and smaller than normal heads. LBVD is soil borne and can also be spread by contaminated farm equipment, mechanical means and with plant debris.
Disease management relies on phytosanitation within and between fields, and exclusion from new areas.
The disease was initially associated with LBVaV which is frequently present in affected plants, but has also been reported from disease free fields, and a causal relationship with LBVD (Koch's postulates) could not be demonstrated. However, when MiLBVV was identified, it was shown that it is consistently associated with LBVD and the disease can be induced by single infections with this virus. Therefore MiLBVV is now considered the main cause of LBVD.
Maps
Saudi Arabia (with regions):
<http://www.the-saudi.net/saudi-arabia/images/saudi-map.gif> and <http://healthmap.org/promed/p/131>
Pictures
Big vein disease of lettuce:
<http://ag.arizona.edu/crop/vegetables/cropmgt/images/az1099no16bvvirus.jpg>,
<http://vegetablemdonline.ppath.cornell.edu/Images/Impt_Diseases/64_Lettuce_Big.jpg>,
<http://bugwoodcloud.org/images/768x512/1571812.jpg>,
<http://bugwoodcloud.org/images/768x512/1571987.jpg>,
<http://ucanr.org/sites/Test1/files/92350.JPG>, and <http://pnwhandbooks.org/plantdisease/sites/default/files/imagecache/image_lightbox/images/LettuceBigVein.jpg>
(compared to healthy)
Photo galleries of symptoms:
<http://www.forestryimages.org/browse/subthumb.cfm?sub=58460&area=93>
(LBVaV) and
<http://www.forestryimages.org/browse/subimages.cfm?sub=56440>
(MiLBVV)
Links
Lettuce big vein fact sheets:
<http://www.vgavic.org.au/pdf/IDO_Update_21Oct10.pdf> and <http://pnwhandbooks.org/plantdisease/node/3473/>
Information on lettuce big vein disease and viruses:
<http://www.ipm.ucdavis.edu/PMG/r441101111.html>,
<http://www.vgavic.org.au/communication/newsletters/lettuce_big_vein_virus.htm>,
<http://apsjournals.apsnet.org/doi/abs/10.1094/PHYTO-98-4-0464>, and <http://link.springer.com/article/10.1023%2FA%3A1023060830841>
Virus taxonomy via:
<http://ictvonline.org/virusTaxonomy.asp?version=2012>
Information on oomycete vector and taxonomy:
<http://link.springer.com/article/10.1007%2Fs10327-005-0239-7>
_P. virulentus_ vector taxonomy and synonyms:
<http://www.speciesfungorum.org/Names/SynSpecies.asp?RecordID=337230>
and
<http://www.speciesfungorum.org/GSD/GSDspecies.asp?RecordID=337230>
- Mod.DHA
A HealthMap/ProMED-mail map can be accessed at:
<http://healthmap.org/promed/p/131>.]
[See Also:
2007
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Big vein virus, lettuce mosaic virus - USA 20070325.1034
2004
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Mirafiori lettuce virus - Chile (Chacabuco Province) 20041105.3002
2003
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Mirafiori lettuce virus - Brazil (Sao Paulo State) 20030614.1462]
Topics
Species
