Worlds Wheat Crop in Peril?

WHEAT STEM RUST, STRAIN UG99: RESISTANCE BREEDING
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Date: 17 Mar 2009
Source: Global Rust Initiative Press Release [edited]Cick on title above to see;



The Borlaug Global Rust Initiative 2009 Technical Workshop (Mexico)
confirmed that the dangerous and newly-emerged stem rust race known
as Ug99 is now in Kenya, Uganda, Ethiopia, Sudan, Yemen and Iran, and
is on the march toward South Asia. According to scientists, longer
distance movement to other regions cannot be excluded. They estimate
that 90 percent of the varieties planted in farmers' fields around
the world lack resistance to the pathogen.

In a new study released at the event, researchers described a
breakthrough in their efforts to develop new varieties of wheat that
are not only resistant to Ug99 but also produce more grain than
today's most popular varieties. Scientists have produced new types of
high-yield wheat that contain what plant breeders call "multiple
minor genes" that have resistance to Ug99. Though this strategy may
not provide the same level of protection as that provided by one or 2
major genes, it is high enough to be effective, and the researchers
believe that by forcing the fungus to overcome a larger array of
genetic barriers, these new wheat varieties could provide long-term
protection against future stem rust mutations.

There are numerous examples in the last century of stem rust mutating
and "defeating" wheat plants that have contained single major
resistance genes. One of the alarming hallmarks of Ug99 is that in
Kenya it has mutated and overcome 2 additional major stem rust
resistance genes called Sr24 and Sr36 that had been effective against
the original form of Ug99.

The response on all fronts has been swift and is producing results
far faster than anyone had expected. For example, researchers in Iran
noted they have begun producing seed of the new varieties for testing
in more extensive field trials. And scientists from India reported
the results of an intensive campaign underway in different regions to
convince farmers that they will need to switch to Ug99-resistant
wheat before the disease arrives in the country. Other efforts are
underway to spur testing and seed production in Egypt, Bangladesh,
Nepal, Ethiopia, and Afghanistan.

Many people involved in the conference said that the unprecedented
effort to combat Ug99 has resulted in a new level of international
scientific collaboration that could provide a range of benefits for
global food production.

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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. As
reported above, an even more virulent variant able to overcome 2
additional resistance genes has recently emerged in Kenya. Rust
spores are carried eastwards on prevailing winds, and regions at high
risk of a Ug99 incursion have been identified accordingly.

It is estimated that Ug99 could reduce world wheat production by 60
million tons (for more information on stem rust and Ug99, please see
previous ProMED-mail posts and links listed below). The apparent good
progress with resistance breeding reported above is largely due to
efficient international cooperation, which has not been achieved
before on this scale and, as such, is a very positive outcome of the
Ug99 global threat.

Maps
Middle East, including Ug99 alert area:

Africa:


Pictures of stem rust symptoms on wheat:
and


Links
Additional news story:
,

and

Information on wheat stem rust:

Information on Ug99:
,
,
and

_P. graminis_ f.sp. _tritici_ taxonomy:

Delhi Declaration on Ug99:

Global Rust Initiative:

- Mod.DHA]

[see also:
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
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]
....................................................dha/msp/jw
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