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PRI's Environmental News Magazine

A Victory Against a Major Wheat Blight

Air Date: Week of October 30, 1992

Laura Knoy reports from Washington on what researchers say is the defeat of wheat rust, a fungus which has been one of the biggest killers of wheat crops throughout history. Rust claims up to 10 million tons of wheat a year around the world.

Transcript

CURWOOD: With rapidly rising population and stocks of wheat and other grains fluctuating in recent years, the balance of the world's food supply is close to precarious. And of course in places such as Somalia, it's already tipped over into disaster. But now comes some good news for a hungry planet: researchers say they've conquered an age-old threat to the world's wheat supplies. From Washington, Laura Knoy has our report.

KNOY: Wheat rust has plagued farmers for thousands of years. In Biblical times, the Romans prayed for mercy from Robigo, the god of rust. Experts estimate today the fungus kills from five to ten million tons of wheat every year. Now the Mexico-based International Maize and Wheat Improvement Center -- known by its Spanish acronym CIMMIT -- claims it has cross-bred a new strain of plant that thrives despite the rust. CIMMIT director Don Winkleman says the center has cornered, if not slain, the wheat rust dragon.

WINKLEMAN: Over the past ten years we've seen no evidence of damaging wheat rust attacks on these plants, anywhere that they're grown. And hence we have declared that we have collared the wheat-rust fungus.

KNOY: Experts say fighting wheat rust is a constant battle. Scientists keep coming up with new strains of rust-resistant wheat, and the fungus keeps mutating into forms that overcome that resistance. Winkleman explains the key to CIMMIT's new plant is a process called "slow-rusting," a trait found in an old Brazilian strain of wheat that CIMMIT cross-bred with modern high-yield varieties. The new hybrid allows a tiny amount of the fungus, or pathogen, to grow on it, but not enough to damage the plant.

WINKLEMAN: The pathogen says, I've got a home here, I can chew on these plants, I'm not going to be, they're not going to put me off completely, I can survive. And the pathogen then would not be so disposed to mutate, create new forms of the pathogen, which would have a dramatic effect on the plant.

KNOY: But some scientists are skeptical "slow-rusting" is the answer.

BROWN: What that may do is slow down the rate at which new strains will evolve, but I don't think it means that the problem has been eliminated.

KNOY: Lester Brown heads the World Watch Institute in Washington, DC. He says plant breeding to fight disease is an unending effort, and lasting solutions are rare. And even though CIMMIT claims its plants have been free of rust damage for ten years, Brown says that's not long enough to declare the fungus has been conquered.

BROWN: I suppose there's a human temptation to want to think you maybe have solved the problem for once and for all. But given the history of plant breeding for pest resistance, that is probably not likely.

KNOY: A World Bank agricultural official agrees. But, he adds, wheat rust is such a big problem, any progress is good. Even CIMMIT director Winkleman seems to back away from the center's first statements about its new plant, that is "defeated" wheat rust. Winkleman admits there's a slight chance the rust will mutate again, and kill the new wheat strain, perhaps many years from now. But Winkleman contends in the meantime, CIMMIT's "slow-rusting" wheat will increase crop yields, and reduce the need for pesticides. For Living on Earth, I'm Laura Knoy in Washington.

 

 

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