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Date: 29 May 2009
Source: Australian Broadcasting Corporation Rural News [edited] <http://www.abc.net.au/rural/news/content/200905/s2583991.htm>

_Tomato yellow leaf curl virus_ has spread through the AUD 70 million [USD 56 million] tomato industry in Bundaberg, costing growers thousands of dollars, and leaving more than 80 percent of some crops infected; 3 years ago [2006] the virus, which stunts tomato growth and is spread by the silverleaf whitefly, was discovered in southeast Queensland, but couldn't be contained.

Queensland Primary Industries and Fisheries plant virologist John Thomas says growers could be forced to change farming practices. "We need better resistance in the cultivars that are suitable for the Bundaberg district, and we also need some agronomic practices to change," he says. "Growing tomatoes 12 months a year is a problem. We really need a gap where there are no tomatoes present to reduce levels of infection, although we really don't know what other plants are affected."

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[_Tomato yellow leaf curl virus_ (TYLCV; genus _Begomovirus_) originates from the Middle East and is one of the most damaging viruses of tomato worldwide. It can also affect a number of other solanaceous and leguminous hosts. Symptoms on tomato include small chlorotic puckered leaves and stunting of plants. Yield losses of up to 80 percent have been reported. The virus is transmitted in a persistent manner by the silverleaf whitefly (_Bemisia tabaci_ biotype B), which in itself is a serious pest of tomatoes and other vegetable crops. It can also be transmitted by mechanical inoculation (poorly) and by grafting, but is not transmitted by seed or contact between plants.

Disease management may include use of certified vector and virus free planting material, cultural practices, and removal of infected crop residues and possible pathogen and/or vector reservoir plants to reduce inoculum. Control of the vector is most important in disease control; however, this may cause problems of chemical residues on the fruit and is extremely difficult in open field situations due to the widespread presence and wide host range of the vector. Field cropping of tomatoes has been abandoned in some areas due to TYLCV. Tomato cultivars with increased resistance are available. Transgenic tomato plants incorporating TYLCV capsid protein genes have been found to be resistant to the virus.

In Australia, TYLCV was 1st reported in 2006 near Brisbane and has spread in southern Queensland since then. The disease has been found in many crops, with infection levels ranging from 5 to 100 percent of plants. TYLCV is considered a major threat to tomato production. This virus was shown to be distinct from _Tomato leaf curl Australia virus_
(TLCV) occurring in the Northern Territory and on Cape York Peninsula.
There are a number of related begomoviruses in the tomato yellow leaf curl and tomato leaf curl clades that cause similar diseases on a range of crops in different areas and can lead to considerable yield losses.

Maps
Australia:
<http://www.ga.gov.au/image_cache/GA4073.jpg>  and <http://healthmap.org/promed?v=-25.7,134.5,4>
Queensland:
<http://www.ozhorizons.com.au/qld/map.gif>

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
Information on TYLCV:
<http://www.eppo.org/QUARANTINE/virus/TYLC_virus/TYLCV0_ds.pdf>  and <http://www2.dpi.qld.gov.au/horticulture/18522.html> (in Queensland, with pictures) TYLCV taxonomy:
<http://www.ncbi.nlm.nih.gov/ICTVdb/ICTVdB/00.029.0.03.043.htm>
Current species in the tomato yellow leaf curl clade via:
<http://www.ncbi.nlm.nih.gov/ICTVdb/Ictv/vn_indxT.htm>
Information on _B. tabaci_ vector:
<http://www.issg.org/database/species/ecology.asp?fr=1&si=106>  and <http://www.eppo.org/QUARANTINE/insects/Bemisia_tabaci/BEMITA_ds.pdf>
- Mod.DHA]