DUBAI, 27 March 2008 (IRIN) - The Ug99 strain of the killer wheat fungus (stem rust), which recently infected wheat farms in western Iran, is a serious threat to global food security, agricultural scientists have warned. They have said the fungus may affect additional wheat-producing countries.

Mahmoud Solh, director-general of the International Centre for Agricultural Research in the Dry Areas (ICARDA), was quoted in a 20 March ICARDA press release as saying that he and his fellow scientists were convinced that Ug99 would quickly spread beyond Iran and that, with the long distance travel of rust spores, Ug99 would soon affect farms in the Middle East, Central Asia, South Asia and East Asia.

Richard Brettell, director of the Biodiversity and Integrated Gene Management Programme at ICARDA, told IRIN on 26 March that halting the spread of the stem rust spores is difficult since they are dispersed by the wind. "The fungus can to some extent be controlled by the application of fungicides [as a spray]; however, these need to be applied at an early stage of infection before the disease takes hold," he said.

Brettell said the most effective way of controlling the disease is to grow resistant varieties. But he warned: "The problem is that almost all the wheat varieties grown in West and South Asia are known to be susceptible to Ug99. It will take time and coordination to replace them with resistant varieties."

The UN Food and Agriculture Organization (FAO) warned in early March that the major wheat-producing countries to the east of Iran should be on high alert. Other areas likely to be affected include the Mediterranean region, north Africa, southern Europe, eastern Europe and Russia.

According to ICARDA, sporadic epidemics of stem rust, also known as black rust, have plagued wheat production before. It cites an outbreak of the disease in North America in the 1950s which destroyed up to 40 percent of the spring wheat crop. Since the discovery of Ug99 in Uganda in 1999, the fungus has infected crops in north and east African countries and in early 2006 it was found in Yemen as had been predicted based on earlier movements of yellow rust.

New variant

Brettell said the pathogen had moved faster than anticipated because it had been able to take a hold on susceptible wheat varieties grown in the Arabian peninsula. "These provided a bridge for it to jump to Iran, most likely being blown by prevailing winds," Brettell said.

Before its appearance in Iran, a country with six million hectares of wheat, stem rust had seriously affected wheat production in Ethiopia, Kenya and Yemen. ICARDA's Solh said that since the pathogen was moving faster than anticipated, surveillance, monitoring and tracking of this new strain was essential for control of the disease.

Brettell explained why Ug99 had defeated varieties that had been resistant to stem rust in the past: The rust fungus had a capacity to mutate and take on new virulence, in a similar way to other pathogens, such as the influenza virus for animals (including birds) and humans. "Ug99 is a new variant of the wheat stem rust pathogen… The problem arises because this new variant has overcome the resistance bred into many of the world's wheat varieties," he said.

Standardised tracking

Following the detection of the fungus in Iran, a two-day Stem Rust Baseline Survey Workshop on Standardising Protocols and International Collaboration was held at ICARDA, Aleppo, Syria, on 10-11 March. It was jointly organised by ICARDA, the International Maize and Wheat Improvement Centre (CIMMYT), FAO and Cornell University, under the Borlaug Global Rust initiative.

The purpose of the meeting was to standardise methods for surveying and tracking the spread of stem rust Ug99, as well as to strengthen international collaboration to combat it.

This, said Brettell, was achieved by bringing together about 49 scientists and researchers from the national agricultural research institutes of Egypt, Eritrea, Ethiopia, Iran, Kenya, Morocco, Nepal, Pakistan, Sudan, Syria, Tunisia, Turkey, Uruguay and Yemen. A number of international research institutes also attended the workshop.

Global effort

ICARDA is putting much emphasis on international cooperation and sharing of knowledge, saying that the fight against Ug99 must be a global effort.

A Global Rust Initiative (GRI) was launched in 2005, and both ICARDA and CIMMYT have been working closely with the US Department of Agriculture, Agriculture Canada, FAO and other national and international organisations to limit the spread of Ug99.

Both ICARDA and CIMMYT have identified resistant wheat varieties, and these are currently under evaluation in national agricultural systems around the world, according to Brettell.

In October 2007 scientists and researchers met in Addis Ababa, Ethiopia and established an early warning system to check the spread of stem rust. A survey system was then set up that would help researchers track and identify the spread of the fungus.

ICARDA, established in 1977, is one of 15 international research centres supported by the Consultative Group on International Agricultural Research. ICARDA serves the entire developing world for the improvement of barley, lentils, and faba (broad) beans; and dry-area developing countries for the on-farm management of water, improvement of nutrition and productivity of small ruminants (sheep and goats), and the rehabilitation and management of rangelands. In the central and west Asia and north Africa regions, ICARDA is responsible for the improvement of durum and bread wheat, chickpeas, pasture and forage legumes and farming systems; and for the protection and enhancement of the natural resource base of water, land and biodiversity.

The Consultative Group on International Agricultural Research (CGIAR) is a strategic alliance of countries, international and regional organisations, and private foundations supporting 15 international research centres that mobilise cutting-edge science to promote sustainable development by reducing hunger and poverty, improving human nutrition and health, and protecting the environment.

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