A ProMED-mail post
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Date: 16 Jul 2010
A major viral disease of tomato caused by a complex of viruses [of genus] _Tospovirus_ has been found in all tomato producing regions of Brazil. It can totally wipe out young tomato seedlings and the only solution is to breed for resistance against the disease. Studies showed that [the disease involves] a complex of [tospo]virus species with different characteristics.
Molecular markers derived from the Sw-5 resistance gene were developed [at the University of Brazil]. They can be used for rapid breeding of resistance into commercial [crop] varieties by differentiating between susceptible and resistant plants. Leonardo Boiteus, Embrapa Vegetables, said that "the system can be used for any type of tomato which is important for seed companies that focus on developing new tomato hybrids."
[Original article in Portuguese:
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Communicated by:
ProMED-mail
[Tospoviruses are an extremely important group of plant viruses capable of infecting a large range of crops. The type member, _Tomato spotted wilt virus_ (TSWV), has one of the broadest host ranges among plant viruses and has had a serious impact on many crop species worldwide. Tospoviruses are transmitted exclusively by thrips, which are found worldwide. Weed species can serve as pathogen or vector reservoirs and tospovirus epidemiology is complex.
Disease management of tospoviruses is difficult but may include vector control (for glasshouse crops), use of clean planting material, control of weed hosts of virus and vectors, phytosanitary measures, and use of resistant crop cultivars. Worldwide, the current commercial resistance of tomato cultivars to TSWV is based on a single dominant gene, Sw-5, which is derived from a wild _Lycopersicon_ species. However, strains of TSWV that overcome resistance based on Sw-5 are emerging (see for example ProMED-mail post 20050329.0914).
In Brazil, 4 tospoviruses have been reported to infect tomato crops:
_Tomato spotted wilt virus_ (TSWV), _Tomato chlorotic spot virus_ (TCSV), _Groundnut ringspot virus_ (GRSV), and _Chrysanthemum stem necrosis virus_ (CSNV). A tospovirus disease complex has been reported to be the main limiting factor for tomato production in the country since the 1990's. Symptoms have been described as purple discolouration of leaves, drooping of leaves, necrotic lesions on stems and fruit, and stunting of plants. There is no evidence of the disease being seed transmitted. Several tomato varieties and hybrids are currently available, but the development of better molecular markers reported above will assist breeders in the race against the emergence of new resistance breaking viral strains.
Maps
Brazil:
Pictures
Tospovirus tomato disease in Brazil:
(affected field) and
(fruit)
TSWV on a range of hosts:
and
Western flower thrips:
Electron micrograph of _Tospovirus_ particles (TSWV):
Links
Embrapa information page on tospovirus tomato disease (in Portuguese):
General information and background on tospoviruses:
TSWV information:
and
Sw-5 resistance gene:
TSWV taxonomy and description:
Genus _Tospovirus_ taxonomy:
Current lists of recognised tospoviruses and their vectors:
Thrips information via:
[see also:
Murda, chilli & mildew, melon - India 20100413.1199
2008
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Red rot, sugarcane & vegetable viruses - Costa Rica: alert 20081017.3293 Tomato zonate spot virus - China: (YU), new tospovirus 20080611.1843 Tomato spotted wilt virus, capsicum - Spain (Almeria) 20080123.0280
2007
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Tomato viruses TSWV, TICV - Jordan: 1st reports 20071223.4123 Tomato spotted wilt virus, tomato - USA (CA) 20070608.1872 Groundnut ringspot tospovirus, peanut - Argentina (Cordoba): 1st report 20070524.1670
2005
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Tomato viruses - Ecuador 20051125.3418
Tomato spotted wilt, Sw5 resistance gene - Italy 20050329.0914
2004
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Tomato spotted wilt, Iris yellow spot, onion - USA (GA) 20041031.2938 Tomato spotted wilt, pepper - Spain 20040605.1519
2003
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Tomato spotted wilt, tomato - USA (FL & GA) 20031009.2539
2002
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Tomato spotted wilt, tomato - USA (MA): Correction 20020627.4618 Tomato spotted wilt, tomato - USA (Massachusetts) 20020626.4608 Tomato spotted wilt, tomato - USA (North Carolina) 20020622.4565 Tomato spotted wilt, tomato - (USA) Virginia 20020620.4545
2001
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Tomato spotted wilt tospovirus, soybean - Iran 20011229.3130 Tomato spotted wilt, peanut - Iran 20011220.3069 Tomato spotted wilt disease, tomato - Kenya 20011109.2778 Tomato viruses - Tunisia 20010926.2349 2000
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Tomato spotted wilt tospovirus, crops - USA (Georgia) 20000617.0989 Tomato spotted wilt tospovirus - Europe 20000302.0286 Tospoviruses - Argentina 20000213.0197 Tospovirus, zucchini, courgette & cucumber - Brazil 20000129.0145]
Topics
Species
