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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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