Saturday, May 31, 2008

First report of Tomato chlorosis virus in Cuba

First report of Tomato chlorosis virus in Cuba
A ProMED-mail post
ProMED-mail is a program of the International Society for Infectious

A ProMED-mail post
ProMED-mail is a program of the
International Society for Infectious Diseases <>

Date: May 2008
Source: The American Phytopathological Society, Plant Disease 2008;
92(5), 836 [edited]

[Ref: Y Martinez-Zubiaur et al: First report of _Tomato chlorosis virus_
infecting tomato in single and mixed infections with _Tomato yellow leaf
curl virus_ in Cuba.
Plant Dis 2008; 92(5), 836; DOI: 10.1094/PDIS-92-5-0836C]

Whitefly-transmitted viruses have caused severe losses in tomato crops
in Cuba. In 2006 and 2007, tomato greenhouses across eastern Cuba
exhibited high levels of _Bemisia tabaci_ (B biotype) infestation. Some
plants showed interveinal chlorosis and a severe yellow mosaic, combined
with leaf brittleness. These symptoms were different from those induced
by _Tomato yellow leaf curl virus_ (TYLCV-IL(CU)).

Only 12 of 31 symptomatic samples resulted in positive PCR [polymerase
chain reaction] assays with TYLCV-specific primers. A reverse
transcription (RT)-PCR analysis for _Tomato chlorosis virus_ (ToCV) with
generic and specific primers was also carried out. Sequence analysis of
the cloned RT-PCR products ['amplicons'] (463 basepairs) confirmed the
presence of ToCV in Cuba. The fragment had 97 to 98 percent identity
with isolates from Spain, Florida (USA), and Reunion Island (France).

Cloned TYLCV and ToCV amplicons were used as probes to reanalyze the
selected 31 samples by a dot-blot hybridization assay [a diagnostic
method using labelled nucleotide sequences of the viruses as 'probes' to
detect the presence of similar sequences in the samples - Mod.DHA] in
search of mixed infections. The assay showed 16 samples to be positive
for ToCV, 4 for TYLCV, 8 for both, and 3 samples were negative. To our
knowledge, this is the 1st report of ToCV and TYLCV/ToCV mixed
infections in Cuba.

Communicated by:

[ToCV (genus _Crinivirus_) has been reported from Europe and a number of
locations in other parts of the world. Besides tomato, it can also
affect capsicum and some solanaceous weeds, which may serve as pathogen
reservoirs, as well as some ornamental and weed species in other
families. Symptoms on tomato leaves include irregular chlorotic mottle,
interveinal yellowing, necrotic flecks, and possible distortions. No
obvious symptoms develop on fruit and flowers, but fruit size and
numbers are reduced due to a loss of photosynthetic area. Significant
yield losses occur as a result, but symptom severity varies with host
cultivars. Symptoms may be confused with nutritional problems and are
also similar to those of the related _Tomato infectious chlorosis 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. Infection of tomato
causes plants to be stunted with small chlorotic puckered leaves. Yield
losses of up to 80 percent have been reported, and
field cropping of tomatoes has been abandoned in some areas due to TYLCV.

Both viruses are transmitted by the whitefly vector _Bemisia tabaci_
(ToCV also by 2 other whitefly species), and outbreaks are usually
associated with high vector populations. Disease management of whitefly
transmitted viruses is difficult and includes vector control, removal of
reservoirs of both virus and vectors, use of crop varieties with
increased pathogen tolerance, and clean planting material. Both ToCV and
TYLCV, as well as their vector _B. tabaci_
are included on the quarantine alert list of the European Plant
Protection Organisation (EPPO). For more information on ToCV and TYLCV
see previous ProMED-mail posts listed below.

Whiteflies have been reported to transmit over 100 virus species. _B.
tabaci_ is believed to be a species complex with a number of recognised
biotypes varying in their distribution and vector activities. Whiteflies
are a common problem in glasshouse grown crops, and multiple infections
with viruses sharing this vector are not unusual. Co-infecting viruses
may interact with a symbiotic enhancement of symptoms (synergism), as
appears to be the case here.

<> and
Worldwide distribution of ToCV (September 2006):
TYLCV worldwide distribution (September 2006):

ToCV symptoms on tomato leaf:
TYLCV symptoms on tomato plants:
<> and
_B. tabaci_ picture gallery:

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