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International Society for Infectious DiseasesA ProMED-mail post
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ProMED-mail is a program of the
International Society for Infectious Diseases <http://www.isid.org>
Date: July 3, 2007
Source: All Africa, East Africa Standard (Nairobi) report
[edited]
<http://allafrica.com/stories/200707021716.html>
About 140 000 hectares of wheat worth millions of shillings
could go to waste this season following an outbreak of the
dreaded wheat stem rust fungus in the country, experts have
warned. The disease has been detected in Narok District, the
highest producer of wheat and barley in the country.
Wheat stem rust is a fungal disease and its symptoms are small
yellow flecks that develop into long, narrow yellow blisters on
the stem, leaves, and leaf sheaths of young seedlings. The
blisters break open, revealing a powdery mass of brick-red
spores. The spores are dispersed by the wind to other plants
where they germinate, invade the plant, and produce more
pustules.
Mr Naphtali Mureithi, executive director of the leading
agrochemical firm Orion East Africa Limited, said it was feared
the disease could spread to Ethiopia and the Middle East
countries, where wheat farming is the main economic activity.
"We have visited wheat fields in Narok with researchers from the
Kenya Agricultural Research Institute
(KARI) to assess the magnitude of the outbreak," Mureithi added.
However, he said planting wheat varieties resistant to the
disease and spraying the affected crops with fungicides could
contain the disease.
Sounding the alarm, Mureithi also said that another 30 000
hectares
(74 132 acres) of barley under cultivation in the same region is
under the threat from barley yellow dwarf virus. Speaking during
a food security meeting in Nakuru at the weekend, Mureithi said
the virus was spreading fast to wheat fields in the neighbouring
districts and called for urgent intervention. "The disease is
ravaging large hectares of wheat in Narok and it is spreading to
the escarpments. This is a serious disease problem which could
cause serious loss to wheat farmers," Mureithi said.
[Byline: Peter Mutai]
--
Communicated by:
J. Allan Dodds
Former ProMED-mail plant disease moderator <dodds@ucr.edu>
[Wheat stem rust (black rust) is caused by the fungus _Puccinia
graminis_ f.sp. _tritici_. It occurs worldwide throughout wheat
producing areas. Yield losses of up to 70 percent occur, and
some fields are totally destroyed. Dispersal is by wind and with
infected straw.
New races are emerging with increased virulence against genes
previously used for resistance breeding. The most dangerous, at
present, is strain Ug99, which was 1st reported in Uganda in
1999.
Recurring epidemics in Kenya and then Ethiopia followed and it
has recently spread to Yemen. It may also be present in
Pakistan, Sudan, and Tanzania. Ug99 is considered to be a
significant threat to global wheat production, and in response
the international Global Rust Initiative was set up.
Although the strain of stem rust causing the outbreak reported
here is not mentioned, it seems likely that it is Ug99.
_Barley yellow dwarf virus_ (BYDV; genus _Luteovirus_, family
_Luteoviridae_) is distributed worldwide and the most
destructive of virus diseases of wheat. Grain yields may be
reduced by one third. It attacks a wide range of grass species
(_Gramineae_) including wheat, oats, rice, maize, rye, and
barley. Symptoms include leaf discolouration from yellow to
purple (depending on the host species), stunting, reduced
tillering, and empty seed heads. The virus occurs in several
strains, which can be transmitted by more than 20 species of
aphids. It cannot be transmitted by seed, pollen, or mechanical
means and cannot survive in stubble or in the soil. Disease
management includes use of resistant cultivars and control of
the aphid vectors.
BYDV was reported for the 1st time in Kenya in 1983, and it has
led to reduced barley and wheat production since its
introduction.
Reference
Wangai, A.W. 1990: Effects of barley yellow dwarf virus on
cereals in Kenya. In P.A. Burnett, ed. World perspectives on
barley yellow dwarf, p. 391-3. Mexico, DF, CIMMYT)
Maps
Kenya:
<http://www.ogiek.org/photo-gallery/kenya-map-big.jpg>
African countries:
<http://www.mapsofworld.com/images/maps_of_world_africa.gif>
Pictures
Stem rust on wheat:
<http://scarab.msu.montana.edu/Disease/DiseaseGuidewebpics/Petewebpics41-50/Img0042.jpg>
and
<http://scarab.msu.montana.edu/Disease/DiseaseGuidewebpics/Petewebpics41-50/Img0043.jpg>
Healthy and BYDV-affected wheat plants:
<http://www.ent.iastate.edu/imagegal/plantpath/wheat/ydwarf/0093.04ydwarfmv.html>
Wheat field with BYDV symptoms:
<http://www.ent.iastate.edu/images/plantpath/wheat/ydwarf/0093.10ydwarfwheat.jpg>
_Luteovirus_ particles, electron micrograph:
<http://www.ncbi.nlm.nih.gov/ICTVdb/WIntkey/Images/c2.gif>
Links
Information on wheat stem rust:
<http://www.ars.usda.gov/Main/docs.htm?docid=9910>
Information on Ug99:
<http://www.sciencemag.org/cgi/content/full/315/5820/1786>
(subscription required) and
<http://www.pestalert.org/viewNewsAlert.cfm?naid=36>
Ug99 distribution and potential global impact:
<http://www.cimmyt.cgiar.org/gis/pdf/UG99postH.pdf>
Ug99 and stem rust resistance genes used in wheat breeding:
<http://www.ars.usda.gov/Main/docs.htm?docid=14649>
_P. graminis_ f.sp. _tritici_ taxonomy:
<http://www.indexfungorum.org/Names/NamesRecord.asp?RecordID=455607>
Global Rust Initiative:
<http://www.globalrust.org/>
BYDV information and pictures of symptoms:
<http://www.agric.wa.gov.au/pls/portal30/docs/FOLDER/IKMP/PW/PH/DIS/CER/FN019_1993.HTM>
BYDV fact sheets:
<http://ohioline.osu.edu/ac-fact/0005.html>
and <http://ipm.ppws.vt.edu/stromberg/smallgrain/biology/wydwarf.html>
CIMMYT (International Maize and Wheat Improvement Center) BYDV
newsletter:
<http://www.cimmyt.org/research/wheat/bydvnews/htm/BYDVNEWS.htm>
BYDV taxonomy:
<http://image.fs.uidaho.edu/vide/descr062.htm>
BYDV strains and list of wheat viruses:
<http://www.fao.org/DOCREP/006/Y4011E/y4011e0o.htm>
Introduction of BYDV to Kenya
<http://www.fao.org/docrep/008/y5968e/y5968e10.htm>
General information on wheat diseases and pathogens
<http://www.apsnet.org/online/common/names/wheat.asp> and <http://www.grdc.com.au>.
- Mod.DHA]
[see also in the
archive:
Barley yellow dwarf virus, wheat - USA (IN, NE) 20070531.1758
Wheat stem rust, strain Ug99 - Yemen (02): government response
20070430.1399 Wheat stem rust, spread: FAO, Global Rust
Initiative 20070414.1241 Wheat stem rust, strain Ug99 - Yemen:
1st report 20070117.0229
2006
----
Wheat stem rust, strain Ug99 - Pakistan: susp., 1st report
20060514.1366 Stem rust, wheat - multicountry: new strains
20060406.1039
2005
----
Wheat stem rust, Ug99, new strain - East Africa 20050928.2849
Wheat stem rust, new strain - Uganda 20050912.2698
2003
----
Cereal viruses, oat, barley - USA (Alaska) 20030405.0832
2002
----
Wheat stem rust fungus, new virulence genes - So Afr
20020814.5049
2001
----
Cereal viruses, wheat - Uzbekistan 20011103.2723 Cereal viruses,
barley, wheat - Tunisia 20010829.2049
1999
----
Crop diseases - Canada (Manitoba) 19990816.1417 Barley Yellow
Dwarf virus alert - New Zealand 19990708.1140] |
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