June 6, 2006
From: ProMED-mail<promed@promedmail.org>
Source: American Phytopathological Society, Plant Disease Notes, June 2006[edited] <http://www.apsnet.org/pd/searchnotes/2006/PD-90-0828B.asp>

First report of Beet black scorch virus in the United States
J. J. Weiland, USDA-ARS, Red River Valley Agricultural Research Center, Fargo, ND 58105; R. L. Larson, USDA-ARS, Sugarbeet Production Lab, Fort Collins, CO 80526; T. P. Freeman, North Dakota State University, Fargo, ND, 58105 and M. C. Edwards, USDA-ARS, Red River Valley Agricultural Research Center, Fargo, ND 58105. Plant Dis. 90:828, 2006; published on-line as DOI: 10.1094/PD-90-0828B. Accepted for publication 18 Mar 2006.

In October of 2005, sugar beet (_Beta vulgaris_ L.) plants exhibiting symptoms of rhizomania caused by Beet necrotic yellow vein virus (BNYVV) (3) were observed in a production field near Greeley, CO. The roots of 7
plants exhibiting moderate to severe symptoms characteristic of this disease were tested using double-antibody sandwich enzyme-linked immunosorbent assay with anti-BNYVV antiserum from rabbits. Of these, only 2 roots exhibiting the mildest symptoms tested positive for BNYVV (all roots tested negative for the presence of the related Beet soilborne mosaic virus (BSBMV). 'Hairy' lateral roots characteristic of the disease were combined from the remaining 5 roots, ground in phosphate buffer, and the supernatant from the suspension was mechanically applied to leaves of _Chenopodium quinoa_ in an effort to isolate an infectious agent. Five days postinoculation (dpi), yellow lesions with necrotic centers were visible on inoculated leaves, well in advance of those typically observed for BNYVV or BSBMV. Lesions exhibiting a similar rate of development on _C. quinoa_ subsequently were induced from extracts of root vascular tissue prepared from 4 of 7 additional beet roots tested from this location. Transfer of the infection from the _C. quinoa_ lesions to 32 healthy _C. quinoa_ and 10 sugar beet plants (hybrid ACH9369; American Crystal Sugar Co., Moorhead MN) resulted in 100 percent infection. Inoculated leaves of _C. quinoa_ exhibited a high density of necrotic local lesions within 3 dpi, whereas inoculated leaves of sugar beet exhibited pinpoint, necrotic to diffuse, chlorotic local lesions evident by 5 dpi. Electron microscopic examination of fixed, ultra-thin sections of symptomatic _C. quinoa_ leaf tissue revealed aggregates of virus-like particles of icosahedral symmetry within the cell cytoplasm. Following a virus minipreparation procedure, nucleic
acid extracted from the partially purified virus was found to be single-stranded RNA by ribonuclease digestion and alone was infectious when inoculated to _C. quinoa_ leaves. The apparently monopartite RNA genome was 3.5 kb long and a candidate for the single coat protein (CP) had a mass of approx. 25 kDa. The sole reference set found in the literature for a virus naturally occurring on sugar beet with similar characteristics was that for Beet black scorch virus (BBSV), a virus recently accepted by the ICTV into the genus Necrovirus within the family Tombusviridae (2). Prior to this communication, BBSV has only been reported in China where it was first documented affecting sugar beet in the late 1980s (1). Using the published sequence of BBSV (Genbank Accession No. AY626780), DNA primers directed to the 3(prime) half of the BBSV genome were used in reverse
transcription-polymerase chain reaction to produce an amplicon from the unknown virus. Sequencing the amplicon revealed 88.8 percent nucleotide sequence identity to the BBSV CP gene and 97% amino acid sequence identity
to the predicted CP gene product. Combined, the nucleotide sequence and physical characteristics confirm the presence of BBSV in a U.S. sugarbeet field for the first time. To our knowledge, this is the 1st report of the occurrence of BBSV outside of China.

References:
(1) Y. Cao et al. Arch. Virol. 147:2431, 2002.
(2) C. M. Fauquet et al. Eighth Report of the International Committee on the Taxonomy of Viruses. Academic Press, New York, 2005.
(3) C. M. Rush. Ann. Rev. Phytopathol. 41:567, 2003.
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ProMED-mail
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[The crop plant sugarbeet, _Beta vulgaris_, develops symptoms of the disease black scorch when infected by the virus beet black scorch virus (family: Tombusviridae, genus: Necrovirus, BBSV).

BBSV was first reported in the late 1980s in China. The virus is responsible for serious damage to the sugar beet crop in the Xinjiang, Ningxia, Inner Mongolia, Gansu, and Heilongjiang provinces of China. BBSV infects sugar beet plants systemically through the roots after transmission with _Olpidium brassicae_ zoospores and causes black scorch symptoms on the leaves. Sugar beets are grown as a commercial source of sucrose (sugar). BBSV can result in significant loss of root yield and sugar recovery.

This article describes the isolation of BBSV from roots of 5 sugarbeet plants collected in the field in Greeley, CO. They had tested negative for beet necrotic yellow vein virus, the cause of rhizomania disease which is a common virus disease problem in the USA. Other plants from the same field were infected with rhizomania. BBSV has previously been reported in China but this is the 1st report in the USA and possibly elsewhere. It remains to be seen if this becomes a major disease problem. The USDA is seeking the development of a suitable test for BBSV (see link), which is an indication that there are concerns.

The only sugarbeet virus posted in ProMED-mail is the unrelated beet pomovirus Q.

Map: <http://www.coloradodirectory.com/greeley/map.html>
Links:
<http://www.pubmedcentral.gov/articlerender.fcgi?artid=1075689>
<http://www.ars.usda.gov/business/docs.htm?docid=13186>
- Mod.JAD]

[see also in the archive:
2005
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Beet virus Q, sugar beet - Iran: 1st report 20051130.3457
2002
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Beet soil-borne pomovirus, sugar beet - Iran 20020418.3980
2001
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Beet pomovirus Q, sugar beet - Belgium 20011219.3065]