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Light at the End of a Tunnel: IAEA Contributes to Global Fight to Stop a Wheat Killer

In this photo the wheat stalks on the left show damage caused by the fungus Ug99, which destroys wheat plants. The wheat stalks on the right are of a variety developed under an IAEA Technical Cooperation project by plant mutation breeding experts using nuclear techniques to develop wheat varieties resistant to Ug99. (Photo: IAEA)

In eastern Africa and the Middle East, a wheat killing fungus, called Ug99, that causes the wheat stem rust disease, is spreading across arable land at an alarming rate, rapidly destroying wheat plants, reducing harvest yields, literally devouring wheat farmers' livelihoods and threatening food security. The regions directly affected by Ug99 account for over 37 percent of the global wheat production. Through the long-standing joint FAO/IAEA collaboration, a recent breakthrough in plant breeding has led to the development of wheat varieties resistant to Ug99. These hardy varieties will protect harvests and farmers' income worldwide.

For millennia, since wheat was cultivated, wheat killing fungi have destroyed crops before harvest and increased hunger. Wheat, literally the "bread of life" for billions, is threatened by wheat stem rust disease. For many farmers in the developing world, the grain's sale provides an irreplaceable source of income. Wheat stem rust is a voracious killer. The black stem rust fungus, or Puccinia graminis, spread across continents in the mid-20th century, and was finally stopped more than 30 years ago by wheat resistant varieties that were developed by the American agronomist, Norman Borlaug, the 1970 Nobel Peace Prize laureate. In the meantime, the fungus has mutated and a once-impervious protection has weakened, until a new wave of deadly plant fungus devastated wheat harvests in Uganda in 1999. It became known as "Ug99".

Easily carried aloft, Ug99's fungal spores can be transported by the prevailing winds for hundreds of miles, potentially even traversing oceans, to ruin distant wheat crops. The fungus infects the wheat stem, feeding on the sap rich in nutrients. The plant, deprived of nutrients, either produces only shrunken and nutritionally poor quality seeds or none at all. From 1999 to 2008, this new strain of wheat rust fungus was recognized in Kenya, Ethiopia, Yemen and the Islamic Republic of Iran. According to experts, the fungus threatens to move to the "bread basket" of Europe, Kazakhstan and Ukraine, followed by India and China.

Ug99 kills most of the globally grown wheat varieties. An epidemic is a real threat. Cooperative global efforts to fight Ug99 intensified following Borlaug's warning that "Ug99 is the most serious threat to wheat and barley in 50 years".

The IAEA in collaboration with the FAO sought to help nations produce mutant wheat varieties resistant to Ug99 through support undertaken at the FAO/IAEA laboratory in Austria. The FAO/IAEA plant breeding and genetics experts use radiation induced mutation techniques, to develop varieties that can withstand drought, saline soil conditions and diseases. Pierre Lagoda, Head of the Plant Breeding and Genetics Section, said, "The robust varieties of rice, wheat, barley, bananas, cassava, indigenous grains and other staple crops that we have developed are contributing to greater food security and agricultural sustainability."

Hardier varieties that have an in-built protection against environmental or fungal threats are developed by inducing "mutations". Seeds are exposed to a minute quantity of radiation, which does not make the seed radioactive, but potent enough to affect which characteristics the plant's DNA will "express". Mutations occur constantly in nature, but it can take hundreds of thousands of years before just the right combination of characteristics is expressed in a plant that allows it to withstand a threat. Using radiation a much higher number of mutations is generated, leading to different characteristics useful for crop improvement. Lagoda explained that "inducing mutations delivers results in a fraction of the time Mother Nature would need, so that we can find a resistance in time to fight a global epidemic."

These "induced" characteristics are the result of the natural mutation process, not of genetic manipulation that "splices in" DNA material from other organisms into the plant under study. The resulting disease-resistant variety not only ensures full harvest and stable incomes, its cultivation requires no fungicide, and whose application is environmentally damaging and often too expensive for farmers in developing countries. The wide-ranging use of mutation induction for crop enhancement is documented in the FAO/IAEA Mutant Variety Database.

The new Ug99-resistant wheat varieties were initiated in the FAO/IAEA laboratories through radiation induced mutation. A multinational effort through an IAEA Technical Cooperation (TC) project, started in 2009, developed in only four years the new resistant varieties in Kenya: after the wheat seeds were irradiated and sown, those that display some resistance to Ug99 are bred further. An important aspect of this success is the foundation that has been laid in Kenya over the years - building human and physical capacity for incorporating mutation techniques in their breeding programme, especially for wheat.

Miriam Kinyua, the Kenyan plant breeder from the Eldoret University's School of Agriculture and Biotechnology coordinating the field screening in this TC project, sent ten kilograms of wheat seed to the FAO/IAEA laboratories in Seibersdorf, Austria, for irradiation. Once planted in Kenya, Kinyua and her colleagues identified eight advanced lines resistant to Ug99. After further testing the Kenyan Ministry of Agriculture officially declared in August 2013 that two advanced mutant lines were accorded the status of varieties that can be safely and successfully cultivated without fear that wheat rust would claim the harvest. About six tonnes of seeds of the new varieties may be made available in September for the next planting season in Kenya. The new varieties will begin the long process to stop and shrink the spread of the wheat killer Ug99.

These new wheat varieties are Kinyua's second success story through radiation induced mutation. Her first innovating success is drought resistant wheat varieties, also developed with the support of the Joint FAO/IAEA Programme.

The current programme to find a Ug99 resistant wheat variety is part of a network of more than 20 Member States, the research station of the International Center for Agricultural Research in the Dry Areas (ICARDA) in the Syrian Arab Republic, the International Maize and Wheat Improvement Center (CIMMYT) with its headquarters in Mexico, the FAO Wheat Rust Disease Global Programme, and the Borlaug Global Rust Initiative, USA.

Last update: 26 Jul 2017

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