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New strain of stem rust on wheat in India

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

A ProMED-mail post
<http://www.promedmail.org>
ProMED-mail is a program of the International Society for Infectious Diseases <http://www.isid.org>

Date: August 2009
Source: Plant Disease [edited]
<http://apsjournals.apsnet.org/doi/abs/10.1094/PDIS-93-8-0840B>

[Ref: Emergence of virulence to Sr25 of _Puccinia graminis_ f. sp. _tritici_ on wheat in India
SK Jain et al
Plant Dis 2009; 93(8), 840; DOI: 10.1094/PDIS-93-8-0840B]
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Stem (black) rust, caused by _Puccinia graminis_ Pers. f. sp. _tritici_ Eriks. & Henn., is one of the most destructive diseases of wheat. It could be controlled through introgression of race-specific resistance genes. However, such resistance is mostly short lived due to emergence of new virulences. For example, resistance genes Sr11, Sr24, Sr30, and Sr31 are no longer effective. Detection of new virulences has remained vital in the evaluation and identification of new sources of resistance. We report here the detection of virulence to Sr25, a gene from _Thinopyrum elongatum_, which had been effective or partially effective against stem rust worldwide, including race Ug99.

A stem rust isolate collected in 2006 from Karnataka (southern India) produced susceptible reactions on the primary leaves of differential genotype 'Agatha' carrying Sr25 and susceptible check 'Agra Local'. To verify virulence to Sr25, single-pustule isolates from this sample were inoculated onto seedlings of 6 additional varieties which all carry Sr25. All these accessions were found susceptible to this isolate, except one, which expressed resistance, indicating the presence of additional gene(s). These genotypes are resistant to Sr25-avirulent pathotypes.

The new pathotype is avirulent to Sr11, 13, 14, 21, 22, 23, 24, 26, 27, 29, 31, 32, 33, 35, 37, 38, 39, 40, 43, and Tmp and virulent to Sr5, 6, 7a, 7b, 8a, 9a, 9b, 9d, 9e, 9f, 9g, 10, 12, 15, 16, 17, 18, 19, 20, 25, 28, 30, 34, 36, 42, Wld-1, and Gt. This pathotype has been designated as 58G13-3 and PKTSC according to the Indian nomenclature and the North American system, respectively. It represents race 40 based on Stakman's differentials [standard variety series to identify stem rust pathotypes. - Mod.DHA] It may have arisen from race 40 through mutation. The type culture of the pathotype has been added to the culture collection at Shimla [Himachal Pradesh, India].

The detection of Sr25 virulence is significant since Sr25 is an important gene to be targeted for breeding wheat cultivars resistant to Ug99. We should use either adult plant resistance and/or combining two or more genes for seedling resistance to enhance the field life of wheat cultivars.

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Communicated by:
ProMED-mail
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[Wheat stem rust is caused by the fungus _Puccinia graminis_ f. sp. _tritici_. Overall yield losses of up to 80 percent are reported, but some fields are totally destroyed. New races are emerging, and the most dangerous at present is strain Ug99, which has overcome the major resistance gene Sr31 used in our current wheat varieties. An even more virulent variant of Ug99 able to overcome the additional resistance genes Sr24 and Sr36 has recently emerged in Kenya.

Rust spores are carried eastwards on prevailing winds, and regions at high risk of a Ug99 incursion were identified accordingly in the Middle East and South Asia. It is estimated that Ug99 could reduce world wheat production by 60 million tons and the pathogen is considered a global threat to food security. Resistance breeding programmes have been set up with international cooperation (Delhi Declaration, see link below) to establish wheat varieties resistant to Ug99.

Maps
India:
<http://www.globalsecurity.org/military/world/india/images/IndiaMap_tourism.gif>
and
<http://healthmap.org/r/008o>
Middle East, including Ug99 alert area:
<http://worldatlas.com/webimage/countrys/me.htm>

Pictures of stem rust symptoms on wheat:
<http://www.cimmyt.org/english/wps/news/2005/sept/images/stem2.jpg>  and <http://www.gov.mb.ca/agriculture/crops/diseases/images/fac15s01.jpg>

Links
Recent news stories on worldwide Ug99 resistance breeding:
<http://www.cbc.ca/canada/calgary/story/2009/07/11/edmonton-government-funding-wheat-fungus.html>,
<http://www.latimes.com/news/nationworld/nation/la-sci-wheat-rust14-2009jun14,0,1661589.story>
and
<http://www.theeastafrican.co.ke/news/-/2558/599222/-/rggp9oz/-/>
Information on wheat stem rust:
<http://www.ars.usda.gov/Main/docs.htm?docid=9910>
Information on Ug99:
<http://www.cimmyt.cgiar.org/gis/pdf/UG99postH.pdf>,
<http://www.pestalert.org/viewNewsAlert.cfm?naid=36>,
<http://www.ars.usda.gov/Main/docs.htm?docid=14649>  and <http://www.agbioworld.org/newsletter_wm/index.php?caseid=archive&newsid=2686>
_P. graminis_ f.sp. _tritici_ taxonomy:
<http://www.indexfungorum.org/Names/NamesRecord.asp?RecordID=455607>
Delhi Declaration on Ug99:
<http://www.icar.org.in/news/DELHI-DECLARATION-ON-WHEAT-STEM-RUST-UG99.htm>
Global Rust Initiative:
<http://www.globalrust.org/>
Background on differential hosts for pathotype identification:
<http://www.ars.usda.gov/Main/docs.htm?docid=10348>.  - Mod.DHA]

[see also in the archive:
Wheat stem rust, strain Ug99: resistance breeding 20090326.1168 Wheat rusts - Kenya, India, Australia 20090312.1019
2008
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Wheat stem rust Ug99 - Australia ex Ethiopia: interception 20081203.3807 Wheat stem rust, strain Ug99 - multicountry: update 20081120.3660 Stem rust, wheat - Australia: (WA) 20080905.2769 Wheat stem rust, strain Ug99 - Iran: 1st rep, alert 20080307.0925
2007
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Wheat stem rust, strain Ug99 - Kenya: new variant 20071217.4054 Wheat stem rust, strain Ug99 - multistate: resistance screening 20071208.3957 Barley yellow dwarf virus & stem rust, cereals - Kenya 20070705.2132 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
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Wheat stem rust, strain Ug99 - Pakistan: susp., 1st report 20060514.1366 Stem rust, wheat - multicountry: new strains 20060406.1039
2005
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Wheat stem rust, Ug99, new strain - East Africa 20050928.2849 Wheat stem rust, new strain - Uganda 20050912.2698
2002
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Wheat stem rust fungus, new virulence genes - So Afr 20020814.5049 2000
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Wheat stem rust in resistant wheat lines - Uganda 20000702.1092
1999
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Stem-rust fungus, mutant, wheat - Uganda 19990519.0812]

 

 

 

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