WHEAT STEM RUST UG99

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WHEAT STEM RUST (UG99) Is Americas Wheat and
Barley Production at Risk?
Rick Bennett, Ph.D. National Program LeaderU.S.
Department of AgricultureAgricultural Research
Service
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HISTORICAL EVIDENCE OF STEM RUST

• Several references to stem rust in the Bible
  related to epidemics - Greeks, Hebrews
• Fragments of stem rust-infected wheat from the
  Bronze Age discovered in Israel

• Numa Pompilius (715-672 BC) established a Roman
  Festival to protect crops from rust through
  prayer and sacrifices to the Gods.
• Aristotle and Theophrastus associated rust
  epidemics to weather
• Severe epidemics occurred in the U.S. in
  1917-22, 1935, 1948, 1951-53, 1956, 1962
  between 10-50 losses in some states

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Wheat Stem Rust
A highly virulent new race, Ug99 (Pgt-TTKS)
appeared in Uganda in 1999
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Spread of stem rust race Ug991999 ? Uganda and
Kenya2003 ? Ethiopia2006 ? Yemen and Sudan
Singh et al. 2008
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Potential Migration Routes of Ug99
Yemen a potential gateway to major wheat
producing areas of Middle East and Asia
Singh et al. 2008
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Potential Migration Routes of Ug99
2008 Ug99 is confirmed in Iran
Singh et al. 2008
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Key question is. How quickly ??

• Assisted international movement
• Tourists and clothing
• Infected (living) plant material
• Long-distance windborne dispersal
• Example 3 day wind event recorded in Feb. 2008
• Yemen through India, Pakistan, into China
• But, little rust development in Yemen at that
  time

May, 2001, a 2,000 km long dust storm
(science.NASA.gov)
Source Dave Hodson, CIMMYT
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Immediate Risk Areas - Initial Assessments by
CIMMYT 1 Billion People 117 Million Tons or 19
of World Wheat Production
5.2 M Ha
5.4 M Ha
12.5 M Ha
Singh et al. 2008
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Vulnerability of Production to New Races of Wheat
Stem Rust Based on 2007 Variety Survey Data
Susc. to Pgt-TTKS Susc. to Sr24
variant Resistant Unknown
Potential losses of 1.4 billion bushels, valued
at over 10 billion
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Reaction of Wheat Germplasm in 2007-08 USDA-ARS
Regional Nurseries to Stem Rust
Susc. to Pgt-TTKS Susc. to Sr24 variant Susc. to
Sr36 variant Resistant

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US Wheat Production and Ending Stocks
U.S. wheat stocks are at an unprecedented 60 year
low
World Wheat Production and Ending Stocks
Global wheat stocks are at the lowest level in
over 30 years
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Global Response and Actions

• Global Rust Summit
• 2005, Njoro, Kenya
• Call to action from Norman Borlaug

• Borlaug Global Rust Initiative

• CIMMYT, ICARDA co-organizers, USDA-ARS
• 1st International Conference, Oct. 2006
• Funding from USAID, USDA, and other donors
• Goal of durable rust resistance in wheat
• Currently pursuing funding from international
  donor agencies

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US Progress on Stem Rust

• USDA-ARS
• Evaluations of US varieties and germplasm to Ug99
• On-site in Kenya 2-3 times per year
• Seedling screening of Ug99 in containment
  facility, 3 mo/yr
• USDA-ARS support for screening US germplasm in
  Kenya
• 3-yr funding 5,000 lines evaluated to-date
• Problems with infrastructure vernalization,
  transplanting of winter wheat
• Future? - recent political instability in Kenya
• DNA Sequence of rust organism complete in 2007
• Begin to understand and target virulence genes
• May facilitate design of avirulence gene
  constructs

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US Progress on Stem Rust

• International germplasm exchange a high priority
• USDA national strategy to mitigate UG99
• Exchange with CIMMYT programs in Turkey testing
  and selection in Kenya
• Valuable resistance genes in wheat relatives
• Original source of many key rust resistance genes
• But, long timeline for introgression and release
  in adapted varieties
• Application of molecular markers to breeding
• Identify, track, and pyramid multiple resistance
  genes
• Facilitate breeding in absence of disease
  screening
• But, few major genes of value remain at this
  point
• Minor genes and adult-plant resistances are
  difficult to identify

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Stem Rust MappingUSDA CSREES NRI Plant Genome
CAP Project
2BL
2BS
2007 Crop Sci. 472013-2020 Tsilo, Jin, and
Anderson
2008 Crop Sci. 48Jan.-Feb. issue Tsilo, Jin, and
Anderson
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SUMMARY

• UG99 is likely to enter the U.S. through natural
  or human induced means
• Up to 50 yield losses could occur regionally and
  locally, particularly in the southern plains if
  fungicides are not used
• New commercially acceptable, highyielding wheat
  and barley varieties with resistance to UG99 will
  not be available for 3-5 years
• Fungicides are currently available which are
  effective against UG99
• USDA is formulating a Coordinated National
  Strategic Plan to identify, monitor, mange and
  control UG99

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Time for a Renewed Commitment to US and
International Agricultural Research
Its not just about productivity and economics,
its now an issue of world food security