‘Super wheat’ resists devastating rust

Stem rust can destroy wheat crops Copyright: Flickr/CIMMYT

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‘Super varieties’ of wheat resistant to the deadly stem rust fungus Ug99 could replace wheat in affected areas in as little as two years — if farmers can be persuaded to adopt them, according to a wheat rust expert.

First discovered in Uganda some 13 years ago, Ug99 is increasingly virulent. It is spreading throughout East and Southern Africa, and spores have also reached as far afield as Iran and Yemen. Wheat breeders had been working on promising resistant varieties in Njoro, Kenya, in the hopes that one of them could combat the fungus.

Now they have bred new varieties with good resistance and with up to 15 per cent better yields than today’s varieties, said Ronnie Coffman, head of the Durable Rust Resistance in Wheat Project at Cornell University, United States.

Stem rust, also known as black rust, is even more damaging than stripe (or yellow) rust which has wiped out about 40 per cent of harvests in Central Asia, the Middle East and North Africa.

The new varieties, developed by wheat breeding expert Ravi Singh and colleagues at the International Maize and Wheat Improvement Center (CIMMYT) in Mexico, are resistant to both rusts. They were unveiled at the 2011 Borlaug Global Rust Initiative’s Technical Workshop in Minneapolis, United States, this week (13–16 June).

The varieties were developed by combining several plant resistance genes, which individually give low levels of resistance but when found together in the same plant make it more difficult for the Ug99 pathogen to unravel their combined defences, providing better resistance.

"We’re trying to raise awareness of these materials and convince farmers that they should adopt them before [wheat rust] grows endemic — especially in countries such as Ethiopia," said Coffman.

Coffman said that the two most critical countries to tackle are Ethiopia and Yemen. However, as Yemen’s political unrest has impeded anti-wheat rust efforts — material recently sent to the country by CIMMYT perished in customs — breeders are initially focusing their efforts on Ethiopia.

"We believe that farmers in Ethiopia will accept the new varieties," he said. "There is a major outbreak of yellow rust (stripe rust) there. It is not nearly as devastating as stem rust, but it’s significant and farmers want something resistant to it.

"These new varieties are resistant to both rusts so we’re hopeful that the incidence of yellow rust will cause them to accept the new varieties. Unless farmers have an incentive that they can see, they don’t tend to accept new varieties."

He said that if the incentive works, the whole of Ethiopia could be growing resistant strains in just two years — and this same timetable could apply to the entire East African region. "But it’s a big if," he added.

Singh said: "We need to see national governments making the investments in seed systems development, including seed production and distribution. In many areas there will need to be support and leadership from wealthy countries and international institutions to carry these innovations into farmers’ fields."

See below for a Borlaug Global Rust Initiative’s educational video about stem rust: