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[1] New Zealand
[2] Serbia
******
[1] New Zealand
Date: July 2008
Source: British Society for Plant Pathology, New Disease Reports
(NDR) vol. 17 (February-July 2008) [edited] <http://www.bspp.org.uk/ndr/july2008/2008-43.asp>
[Ref: LI Ward et al: First report of _Iris yellow spot virus_ on
_Allium cepa_ in New Zealand. BSPP New Disease Reports, vol. 17]
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During a disease survey of _Allium_ crops in New Zealand in
2007, characteristic diamond-shaped lesions, suggestive of _Iris
yellow spot virus_ (IYSV; genus _Tospovirus_, family
_Bunyaviridae_) infection, were observed on a few brown onion
seed plants in the Blenheim area of the South Island (Fig. 1).
The plants with symptoms tested positive for IYSV using a
DAS-ELISA [double antibody sandwich-enzyme-linked immunosorbent
assay]. Total RNA was extracted from the scape lesions and
tested by RT-PCR [reverse transcriptase polymerase chain
reaction]. Amplicons of the expected size were cloned and
sequenced. Sequence comparisons showed 98-100 percent nucleotide
identity with other IYSV N [nucleocapsid] gene sequences in
GenBank [database]. A phylogenetic analysis of the deduced amino
acid sequences of the N gene showed that the New Zealand isolate
of IYSV grouped most closely with isolates from California and
Texas, USA (Fig. 2).
Samples from a further 28 _Allium_ crops (100 plants per crop)
and 4 ornamental _Allium_ species (one plant of each: _A.
senescens_, _A.
murryanum_, _A. caesium_ and _A. moly_), collected around New
Zealand, were tested for IYSV by ELISA. The results showed that
IYSV was widespread in onion (10 of 12 crops) and shallot (3 out
of 3 crops), in both the North and South Islands. However, all
13 garlic crops tested negative. The infected crops showed a
significant amount of thrips damage, but most plants had no IYSV
symptoms. Two of the ornamental _Allium_ species (_A. senescens_
and _A. murryanum_), which were also without symptoms, tested
positive for IYSV by ELISA.
Unfortunately attempts to amplify the viral genome by RT-PCR for
sequencing were unsuccessful.
Reports of new IYSV outbreaks continue to be made from different
parts of the world and the virus is a major production
constraint to onion bulb and seed production in some countries.
This is the 1st report of IYSV in onion and shallot in New
Zealand and its economic impact on these crops in New Zealand is
still to be determined.
Figure 1: Diamond-shaped lesions characteristic of _Iris yellow
spot virus_ on the scape of an _Allium cepa_ plant.
<http://www.bspp.org.uk/ndr/july2008/2008-43-1.jpg>
Figure 2: _Iris yellow spot virus_ phylogeny (Neighbor Joining
Method) based on deduced amino acid sequences of the complete
nucleocapsid gene. The New Zealand isolate of IYSV is indicated
as NZ.
<http://www.bspp.org.uk/ndr/july2008/2008-43-2.jpg>
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******
[2] Serbia
Date: August 2008
Source: The American Phytopathological Society, Plant Disease
2008;
92(8): 1247 [edited]
<http://apsjournals.apsnet.org/doi/abs/10.1094/pdis-92-8-1247a>
[Ref: A Bulajic et al: First report of _Iris yellow spot virus_
on onion (_Allium cepa_) in Serbia. Plant Dis 2008; 92(8): 1247;
DOI:
10.1094/PDIS-92-8-1247A]
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_Iris yellow spot virus_ (IYSV; genus _Tospovirus_, family
_Bunyaviridae_) is established in several European countries
(France, Italy, The Netherlands, Poland, Slovenia, Spain, and
the UK) and its distribution in the EU region has increased
since 2002. In July 2007, symptoms resembling those of IYSV were
observed in an onion (_Allium
cepa_) seed crop in the Sirig locality in Serbia. Onion plants
exhibited characteristic symptoms of chlorotic or necrotic
spindle and diamond-shaped lesions on the leaves and scapes.
Symptomatic plants were found throughout the field and disease
incidence was estimated at 80 percent.
Leaf and scape samples were tested for the presence of IYSV and
2 other tospoviruses, _Tomato spotted wilt virus_ (TSWV) and
_Impatiens necrotic spot virus_ (INSV), using commercial
double-antibody sandwich (DAS)-ELISA diagnostic kits. All
samples tested negative for TSWV and INSV. IYSV was detected
serologically in 26 of 34 onion samples. To determine an
experimental host range, samples of IYSV-infected onion plants
were homogenized and host plants were inoculated with the sap.
Mechanical transmission of the virus occurred rarely. All
inoculated test plants were assayed by DAS-ELISA and only 4
species tested positive for IYSV, but not in all replications.
Inoculated _Chenopodium quinoa_ developed local chlorotic
lesions, _Nicotiana tabacum_ cvs. Samsun and Prilep showed mild
mosaic, while infected _N. benthamiana_ were symptomless
[symptom development on these species is used as a biological
assay for virus identification - Mod.DHA]
For further confirmation of IYSV, conventional reverse
transcription (RT)-PCR was performed on extracts made from
symptomatic onion leaf material and from the ELISA-positive
symptomless leaves of _N.
benthamiana_. A product of the correct predicted size (896
basepairs) was obtained from each of the plants assayed, and one
isolate was sequenced. Analyses revealed 86 to 97 percent
sequence identity with the corresponding gene from all other
IYSV [isolates]. The highest identity (97 percent) was with leek
and onion isolates from Spain.
To our knowledge, this is the 1st report of IYSV infection of
onion seed crop in Serbia. Thorough inspections and subsequent
testing would be needed to establish the distribution and
incidence of IYSV in Serbia.
--
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[IYSV has only recently been confirmed as a member of the genus
_Tospovirus_ by the International Committee on the Taxonomy of
Viruses (ICTV). It has been included in the Alert List of the
European Plant Pathology Organisation (EPPO). Known hosts
include onion, leek, iris, amaryllis, lisianthus, and weeds
including wild relatives of onion (_Allium_ species). IYSV has
been reported from a number of locations in the Americas,
Europe, Asia, South Africa, and Australia. The economic impact
is low in some areas, but up to 100 percent loss has been
observed in onion crops, for example, in Brazil.
The virus is transmitted by the onion thrips, _Thrips tabaci_.
Spread of IYSV occurs with infected plant material and
viruliferous [virus-carrying] vectors.
Ornamentals and weeds may serve as pathogen reservoirs since
thrips may also feed on them. The virus appears not to be seed
transmitted.
_Tospovirus_ epidemiology is complex and natural resistance
appears to be rare amongst their plant hosts. Management of IYSV
and its vector includes the use of clean propagative material,
cultural practices, and pesticides.
_Tomato spotted wilt virus_ (TSWV) and _Impatiens necrotic spot
virus_ (INSV) also belong to the genus _Tospovirus_. This is an
extremely important group of plant viruses affecting a large
range of crops, and new members are being discovered frequently.
Maps
New Zealand
<http://www.backpack-newzealand.com/images/new-zealand-map.gif>
and
<http://healthmap.org/promed?v=-42.4,172.7,5>
Serbia and neighbouring countries:
<http://www.commondreams.org/kosovo/kosovoimages/bceurope1.jpg>
IYSV worldwide distribution (December 2005):
<http://www.eppo.org/QUARANTINE/Alert_List/viruses/maps/IYSV00_map.htm>
Pictures
IYSV symptoms on onion plant:
<http://www.columbiapublications.com/onionworld/marchapril2006/irisyellowspot%20K8.jpg>
and
<http://www.apsnet.org/online/feature/tospovirus/images/figure4.JPG>
IYSV lesions on onion leaf:
<http://www.bspp.org.uk/ndr/july2005/2005-33-2th.jpg>
Electron micrograph of _Tospovirus_ particles (TSWV):
<http://www.rothamsted.bbsrc.ac.uk/ppi/links/pplinks/virusems/b6.jpeg>
Onion thrips vector:
<http://www.insectimages.org/images/768x512/1327078.jpg>
Links
Information on IYSV:
<http://www.eppo.org/QUARANTINE/Alert_List/viruses/IYSV00.htm>
Control of IYSV and the thrips vector:
<http://www.capitalpress.info/main.asp?SectionID=94&SubSectionID=801&ArticleID=39055&TM=77286.9>
_Tospovirus_ taxonomy and species list:
<http://phene.cpmc.columbia.edu/ICTVdB/00.011.0.05.htm>
Current list of recognised tospoviruses:
<http://www.oznet.ksu.edu/tospovirus/tospo_list.htm>
_Tospovirus_ resource centre:
<http://www.oznet.ksu.edu/tospovirus/welcome.htm>
General information and background on tospoviruses:
<http://www.apsnet.org/online/feature/tospovirus/Top.html>
ICTV:
<http://www.ictvonline.org/virusTaxonomy.asp?bhcp=1>
Description and management of onion thrips:
<http://www.nysaes.cornell.edu/ent/hortcrops/english/thrips.html>
and <http://www.ipm.ucdavis.edu/PMG/r584300111.html>
EPPO quarantine Alert List:
<http://www.eppo.org/QUARANTINE/Alert_List/alert_list.htm>.
- Mod.DHA]
[see also
in the
archive:
Iris yellow spot virus,
onion - Germany: 1st rep.(RP) 20080320.1072 Iris yellow spot
virus, multicrop - UK, Canada: 1st reps 20080221.0698
2007
----
Iris yellow spot virus, onion - South Africa: 1st rep
20070920.3129
2006
----
Iris yellow spot virus, onion - Peru: 1st report 20060225.0612
2005
----
Iris yellow spot virus, onion - Chile 20051128.3444 Iris yellow
spot virus, onion - Spain: 1st report 20051121.3384 Iris yellow
spot, onion - India (Maharashtra): 1st rep. 20050507.1266 Iris
yellow spot, onion - France (Reunion Island): 1st report
20050502.1219 Iris yellow spot, onion - USA (OR) 20050112.0110
2004
----
Tomato spotted wilt, Iris yellow spot, onion - USA (GA)
20041031.2938 Iris yellow spot virus, onion - USA (NM)
20040911.2529 Iris yellow spot virus, onion - USA (WA)
20040215.0492
2002
----
Iris yellow spot virus, onion - USA (Colorado) 20020614.4495] |
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