Stem rust: Ancient wheat plague threatens crops anew

Diseases that ravage wheat fields are as old as time itself. The ancient Romans even had a legend to explain the terrible plagues.

According to the myth, a mischievous young boy tied a flaming wheat straw to a fox’s tail, torturing the animal. This single act angered the Roman god Robigus so much that he unleashed a rust-colored plague on the fields that turned all the crops to black.

“Stem rust, when it goes epidemic, destroys a crop,” said Ronnie Coffman, a leading expert on wheat disease and chair of the department of plant breeding and genetics at Cornell University.

“There is nothing left but black stems, zero grain. It is just an absolute devastation,” said Coffman.

The last major epidemic of the fungal disease known as stem rust broke out in 1953 but was quelled with the introduction of a resistant strain of plants in the 1970s, an initiative spearheaded by the late Norman Borlaug, the Nobel Peace Prize winner widely known as the father of the Green Revolution.

In 1998, a new wave of the fungus known as Ug99 turned up in Uganda, overcoming crops that were once resistant and wielding the potential to kill as much as 90% of the world’s wheat.

The disease is now widespread in eastern Africa and threatens to move deep into the Middle East and Asia, where it could devastate farms, cause rising bread prices and unleash political and economic unrest, experts say.

Already, the strain has shown up in Iran and in Yemen.

Rising food prices have also been a factor in a series of uprisings across the Arab world, Mexico, Haiti and beyond.

“Yemen is a big problem,” said Coffman, who as Borlaug’s one-time doctoral student is now carrying on his mentor’s lifelong mission to spread strong crops around the world and provide steady food sources to the poor. Borlaug died in 2009.

Bone of contention
Winds can transport spores as many as 160km per day, raising concerns among scientists about where the epidemic could turn up next.

“From Yemen, the wind currents are such that it could be carried to almost any part of the world — winds blow into south Asia, they blow into central Asia, they blow into Europe even,” said Coffman.

From South Africa, winds could send the plague to the southern cone of Latin America or to Australia, both areas that grow tremendous amounts of wheat.

Wheat makes up one-fifth of the world’s food and is second only to rice in the diets of people in developing countries.

Kenya is one country that is already grappling with a crisis in wheat production, with small farmers facing a loss of as much as 70% of their yield, according to Peter Njau, an expert at the Kenya Agriculture Research Institute.

Large-scale farmers who can afford chemicals to kill the fungus still face rising costs of production, as much as 40% higher than in normal years, said Njau.

The price of a bag of wheat has risen by about a third, and spiking fuel costs combined with a recent reduction on import tax for wheat will put a squeeze on local farmers unseen in many years, he said.

“The farmers, when they harvest their crop, they will end up being paid less for their product and that might be a bone of contention between the farmers and the government,” he said.

Kenya is working with experts at Cornell University and in Mexico to deliver new strains that may be able to resist the latest wave of stem rust.

Experts from around the world are heading to Minnesota next week to share their latest research, as part of an annual meeting by the Borlaug Global Rust Initiative project begun in 2005.

Some new approaches include attempting to combine multiple resistant genes into a single plant so that it will withstand any mutations that might allow stem rust to take over again, and creating plants that allow some stem rust to infiltrate so that the fungus doesn’t mutate into a new super strain.

“Significant progress” has been made, with some new varieties even boosting yields by up to 15%, according to Ravi Singh of the International Maize and Wheat Improvement Centre (CIMMYT) in Mexico.

But funding remains a key obstacle, and Singh said world governments must now take steps to replace their wheat crops.

“Scientists can only do so much,” Singh said. “We need to see national governments making the investments in seed systems development.” – AFP


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