Back in the 1950s, North America saw 40% of the continent’s spring wheat crop lost to stem rust fungus infections. In the late 80s, yellow rust went on a rampage across North Africa, the Middle East and South Asia causing crop losses worth over 1 billion US Dollars. In 2007 and beyond, the world could be facing an even more devastating outbreak by a new strain of the fungus.

Strain Ug99 was first isolated in Uganda and Kenya in 1999. Subsequent research has proven the susceptibility of most wheat cultivars to the fungus. Researchers with the Global Rust Initiative and the United States Department of Agriculture have confirmed that Ug99 is currently infecting wheat crops in Yemen. This is in accordance with a 2005 CIMMYT study which projected a spread from East Africa to North Africa, the Arabian Peninsula and on into Asia.

The researchers predict that annual losses of up to 3 billion US Dollars could occur should the spread continue as predicted. Efforts by GRI scientists to produce resistant wheat material are underway, but will take time to implement. Nobel Laureate wheat scientist Norman Borlaug commented on the situation: "If we fail to contain Ug99 it could bring calamity to tens of millions of farmers and hundreds of millions of consumers. We know what to do and how to do it. All we need are the financial resources, scientific cooperation and political will to contain this threat to world food security."

READ MORE! Ravi Singh of the International Maize and Wheat Improvement Center (CIMMYT) is one of the authors of a paper in CAB Reviews that highlights the threat of migration of Ug99.

Download the CAB Reviews article in pdf format

  Singh points out that “Detection and spread in East Africa of race TTKS, commonly known as Ug99, is of high significance as most wheat cultivars currently grown in its likely migration path, i.e. to North Africa through Arabian Peninsula and then to Middle East and Asia, are highly susceptible to this race and the environment is conducive to disease epidemics.”

Singh highlights strategies for developing wheat cultivars that are resistant to the disease. He explains the role of the GRI in monitoring the further migration of this race. The GRI will also, facilitate field testing in Kenya or Ethiopia of wheat cultivars and germplasm developed by wheat breeding programmes worldwide, understand the genetic basis of resistance especially the durable type, carry out targeted breeding to incorporate diverse resistance genes into key cultivars and germplasm, and enhance the capacity of national programmes.

Singh notes that some wheat genotypes that combine stem rust resistance with high yield potential and other necessary traits have been identified, but that these need rigorous field testing to determine their adaptation in target areas.

The GRI team predicts that annual losses of as much as US$3 billion in Africa, the Middle East and south Asia alone are possible.

The paper, “Current status, likely migration and strategies to mitigate the threat to wheat production from race Ug99 (TTKS) of stem rust pathogen”, by Ravi P. Singh, David P. Hodson, Yue Jin, Julio Huerta-Espino, Miriam G. Kinyua, Ruth Wanyera, Peter Njau and Rick W. Ward, appears in CAB Reviews: Perspectives in Agriculture, Veterinary Science, Nutrition and Natural Resources 2006 1, No. 54. at

Download the CAB Reviews Article in pdf format


  1. Mohd Anwar khan on 28th March 2007 at 2:30 pm

    I don not think that wheat (PBW343) grown in punjab will be having any type of threat from Ug99 as the temperature in wheat season here never goes too much high to welcome stem rust here. Moreover we have never seen stem rust on wheat here.

  2. Tim Holmes on 13th April 2007 at 4:01 pm

    I hestitate to share your optimism on that point given the information presented in Ravi Singh’s CAB Review (see link in article). He claims that PBW343 is highly susceptible to Puccinia graminis Ug99. Also, the CAB Abstracts database contains a number of records for papers which reference the occurrence of the disease in northern India. Singh makes the point that the detection of Ug99 should be a reminder for scientists and farmers not to be complacent about potential disease threats.

  3. Dr Lakshman Prasad on 4th February 2008 at 6:54 am

    I have seen stem rust disease in the wheat field of My University jurisdiction area (Western Uttar Pradesh, India) frequently during last 3 years. I am in doubt about other stem rust of wheat near future. Farmers of this area grown wheat later in season, therefore, crop plants stand in field up to March-April or higher temperature. Thence, this area may be in threats of Ug99 to wheat crop varieties.

  4. ashok jaybhaye on 11th June 2008 at 11:23 am

    Are there any markers available in public domain with which we screen the lines for stem rust (ug 99) resistance.

  5. common Japanese words on 31st March 2009 at 1:55 am

    I have never heard of this type of fungus before, but losing 3 billion in crops would be absolutely devastating to that region.

  6. D. P. Singh on 18th November 2009 at 10:29 am

    Simply presence of a race of rust (Ug 99 or any other) and its entry to any country does not make any sense. It should be able to multiply at given time and space and produce multiple crops of uredospores before grain filling stage of wheat crop then only it may be considered important biotic stress. Can any one indicate the temperature range on which uredospores of Ug 99 germinate and period to produce visible sori? It is needed to develop strategies for managing any possible threat of Ug 99 in different agro-climatic zones in a given country.

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