CIMMYT E-News, vol 4 no. 9, September 2007
In the battle to prevent a global wheat crop catastrophe from an unchecked airborne fungus, scientists use monitoring stations in Ethiopia to enhance their arsenal. But the job is not easy.
“We need manpower development, facility development, irrigation facilities, also some strengthening of the laboratories—pathology laboratory, tissue culture,” says Bedada Girma, the national cereals research program coordinator for the Ethiopian Institute of Agricultural Research (EIAR). “We have the land and the potential and also the manpower, the young scientists. If these are trained, and if we really continue hand in hand with the international community, we will come up with good results.”
This call for help and offer to help are very real. The Kulumsa research station in the Ethiopian highlands, 140 km southeast of the capital, Addis Ababa, is one of the few locations in the world where scientists can test wheat to see if it can resist a strain of the fungal stem rust disease known as Ug99. That is because testing can only be done in areas of the world where the strain has established itself. Scientists have to bring the wheat to the pathogen because it is far too dangerous to take the pathogen to the wheat. Together with the Njoro research station in Kenya, Kulumsa and another station in Ethiopia form the real strategic front against the continually advancing disease. For this reason EIAR is a vital partner in the Global Rust Initiative (GRI), a consortium of international and national institutions working to find a solution to the tremendous threat posed by the new strains of stem rust.
In the twentieth century stem rust was one of the most devastating diseases of wheat around the world. In 1954, for example, it destroyed more than a third of the North American winter wheat crop. Work by Norman Borlaug and a dedicated team of plant breeders developed wheats with resistance to the airborne fungus that held for nearly half a century. But just like human influenza, the stem rust mutated over time and in 1999 a new strain was identified in Uganda. Named Ug99, it appeared able to bypass or defeat the defense mechanisms (coded for by resistance genes) in what had previously been rust-resistant wheat. In tests on more than 11,000 different wheat lines at Kulumsa, Debra Ziet (also in Ethiopia) and Njoro, most of the world’s wheat has now been proven susceptible to the new form of the disease. In late 2007 scientists confirmed the stem rust had spread to Yemen, following a path that points to Iran, Pakistan, and India.
“Kulumsa is a linchpin in our work to find resistance to Ug99 before it spreads to the major wheat-growing areas of the world,” says Rick Ward, the CIMMYT researcher who coordinates the GRI.
Ethiopia itself has good reason to be worried about Ug99. Wheat is the second most widely-grown crop in Ethiopia after maize. It is usually grown by smallholder farmers, so the impact of a devastating fungal disease on food security and livelihoods is potentially very severe. That is why Girma is so worried. “This new race is moving. It has already been identified in Yemen and if we are not prepared there is no reason that it wouldn’t create disaster,” he says.
The Kulumsa station is now screening wheat from Pakistan, Yemen, and Egypt in particular but also material from many other countries. To help ensure the fungus can get a hold on the test wheats if they are susceptible, the test rows are interspersed with rows of a known susceptible variety. In this case it is PBW343, the most widely grown wheat variety in India. Even though the wheat crop is quite young, the PBW343 rows already show the reddish blotches on their stems that indicate the presence of the rust, and within a couple of weeks it will have spread to any susceptible varieties that have been planted—and by then Ug99 will have killed most of the PBW343 plants.
Scientists with the Global Rust Initiative are worried that the fungus may actually have more than one form or strain with small genetic differences making breeding for resistance much more difficult. For that reason, wheats are being screened simultaneously at both Kulumsa and Njoro to test for geographic differences in the disease.
“We have sent 100 entries [different what types] to Kenya this season and we are going to go there and evaluate our material,” says Girma. In Kulumsa his team has identified some potentially resistant wheats and has also tested some promising material from CIMMYT and the International Center for Agricultural Research in the Dry Areas (ICARDA).
For more information: Richard Ward, GRI Coordinator (firstname.lastname@example.org)