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For the 1st time in California, agricultural officials confirmed finding what some call the worst tomato virus in the world -- tomato yellow leaf curl virus.

"It's a significant threat to tomato growers in the state," says Bob Gilbertson, a University of California (UC), Davis, plant pathologist. "Right now, all of the varieties in California should be considered susceptible."

Florida and Georgia growers have battled the viral disease since the early 1990s, and breeders have developed resistant varieties for Southeastern markets, he says.

The whitefly-spread disease was confirmed last year [2006] in Texas and more recently in Arizona and northern Mexico.

UC Cooperative Extension farm advisor Eric Natwick discovered the disease in a high school greenhouse in Brawley in the Imperial Valley. The plants had been grown from seed, and none had been moved outside.

Because the virus is not seed-transmitted, Gibertson says infested silverleaf whiteflies most likely brought it into the greenhouse.

The California Department of Food and Agriculture is working to minimize the outbreak.

Whiteflies can acquire the virus in as few as 5 minutes of feeding and remain infected for life, he says.

Infected tomato plants develop severely curled, yellowing leaves, shattered nodes and short, upright stalks. The virus causes flowers to abort, lowering fruit set and reducing yields. Plants are stunted and upright. Symptoms are most visible on the growing tips of plants.

"It would be difficult to confuse this with too many other diseases," Gilbertson says.

If you suspect you have the virus in your field, contact the local farm adviser or Gilbertson at <RLGilbertson@ucdavis.edu>. The university has developed a diagnostic test that can confirm the disease within 24 hours

J. Allan Dodds
Former ProMED-mail plant disease moderator
Professor of Plant Pathology
College of Natural and Agricultural Sciences
University of California
Riverside, CA 92521
USA
<dodds@ucr.edu>

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[2] Texas - disease originating from transplant facilities

Date: April 2007
From: ProMED-mail <promed@promedmail.org>
Source: The American Phytopathological Society (APS), Plant Disease [edited]
<http://www.apsnet.org/pd/searchnotes/2007/PDIS-91-4-0466A.asp>

Tomato yellow leaf curl virus (TYLCV), a monopartite virus in the genus _Begomovirus_ (family, _Geminiviridae_) from the Middle East, is one of the most damaging whitefly-transmitted viruses of tomato (_Lycopersicon esculentum_) worldwide. TYLCV was 1st identified in the United States in 1997 in Florida (4), and most recently, in the Pacific Coast states of Mexico where fresh market tomatoes are grown for the U.S. market (1). During September 2006, tomatoes grown from transplants in Waller County, TX, exhibited shortened internodes, stunting and puckering of leaflets, green vein banding, and diffuse chlorosis. The disease incidence in 2 fields (4 hectares (ha) total (10 acres) was 95 percent and yield was substantially reduced. Many of the transplants were symptomatic at planting. The transplants originated from 2 facilities in Hidalgo County, TX. Both facilities had experienced heavy infestations of the whitefly, _Bemisia tabaci_ (Genn.), during transplant production. At the same time, transplants produced in Uvalde and Bexar counties, TX, where whitefly infestations were also prevalent, had similar virus symptoms. Total DNA was extracted from the leaves of symptomatic tomato plants from 10 samples from these 4 counties and amplified by PCR (2). DNA samples from Waller, Hidalgo, and Uvalde counties were cloned, and a partial fragment of the viral coat protein gene (core Cp) was sequenced. Blast analysis of the core Cp sequences of each sample confirmed the presence of TYLCV. No other begomovirus was detected, and all attempts to amplify a bipartite begomovirus by PCR (polymerase chain reaction) using degenerate DNA-B specific primers (3) were unsuccessful. The full-length TYLCV DNA was amplified from 3 samples using the rolling circle amplification method as described (1), cloned, and the sequences were determined. The 3 sequences shared 99.6 to 100 percent nt identity and so only one sequence was deposited in the NCBI (National Center for Biotechnology Information) GenBank database (Accession No. EF110890) (1). Analysis of the complete genome nucleotide sequence corroborated TYLCV identity predicted by core Cp analysis that was 98.1 percent identical with TYLCV from Egypt (GenBank Accession No. AY594174) and Spain (GenBank Accession No. AJ489258), 97.6 percent with TYLCV from Mexico (GenBank Accession No. DQ631892), and 96.5 percent with TYLCV-Is (GenBank Accession No. X15656). Additionally, a Southern blot with TYLCV as the probe detected replicating (double-stranded) TYLCV DNA in all samples consisting of 3 plants from Uvalde County and 21 plants from Bexar County. To our knowledge, this is the 1st report of TYLCV in Texas that occurred in 2 transplant production areas approximately 400 km apart. Transplants produced in Uvalde and Bexar counties were planted there, while Hidalgo County transplants were shipped outside of the usual range of the whitefly. Hidalgo County has a subtropical climate, which can allow overwintering of TYLCV and the whitefly vector, allowing the establishment and spread of this virus in the future.
[Byline: T. Isakeit, A. M. Idris, et al]

References:
1. J. K. Brown and A. M. Idris. Plant Dis. 90:1360, 2006.
2. J. K. Brown et al. Arch. Virol. 146:1581, 2001.
3. A. M. Idris and J. K. Brown. Phytopathology 88:648, 1998.
4. J. E. Polston et al. Plant Dis. 83:984, 1999.

ProMED-mail
<promed@promedmail.org>

[TYLCV infection of tomato causes plants to be stunted with small chlorotic puckered leaves and fruit yield to be much decreased. The virus is transmitted by a whitefly vector _Bemisia tabaci_ in a persistent manner; can be transmitted by mechanical inoculation (poorly) and by grafting; not transmitted by contact between plants. Disease control possible by control of the vector. Resistant tomato cultivars are available.

Map of TYLCV worldwide distribution
<http://www.eppo.org/QUARANTINE/virus/TYLC_virus/TYLCV00_map.htm>
Pictures of symptoms
<http://www.avrdc.org/LC/tomato/tylcv05big.jpg>,
<http://www2.dpi.qld.gov.au/images/13644.jpg>,
<http://creatures.ifas.ufl.edu/veg/leaf/TYLCV.jpg>
Links
Current issue of Plant Disease
<http://www.apsnet.org/pd/current/>
TYLCV information:
<http://image.fs.uidaho.edu/vide/descr840.htm>,
<http://www.defra.gov.uk/planth/pestpics/qic2004/QIC55.pdf>,
<http://www2.dpi.qld.gov.au/health/4250.html>

- Mod.DHA]

[see also in the archive:

Yellow leaf curl, tomato - USA (AZ): 1st report 20070226.0694

2006
Yellow leaf curl, tomato - Australia (QLD): 1st rep 20060330.0967
Yellow leaf curl, tomato - Multicountry: 1st reports 20060304.0702

2001
Tomato yellow leaf curl virus species 20010622.1187

1998
Tomato yellow leaf curl begomovirus: spreading 19980528.1026

1997
Tomato yellow leaf curl virus and citrus canker - USA (Florida) 19970903.1869]

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