Genetic Resistance Bred Into Wheat Wears Down

1.34 p.m. ET (1834 GMT) March 26, 1999
By Mark Stevenson

MEXICO CITY — Genetic resistance bred into wheat crops 40 years ago has begun to break down, resurrecting the threat of crop plagues not seen since the last major outbreak in the United States in the 1950s, a nonprofit wheat group said Thursday.

A new, mutated form of the stem-rust fungus — a disease that virtually disappeared from the face of the Earth after destroying as much as half of wheat yields decades ago — reappeared several weeks ago at an experimental farm in the rainy highlands of Uganda.

The reappearance of the wind-borne spores, which corrode the plants' stems, threatens a genetic fix introduced during the "Green Revolution" in the late 1950s and early 1960s, scientists from the Mexico City-based International Wheat and Maize Improvement Center said. The nonprofit group discovered the fungus.

They made the announcement as U.S. Agriculture Secretary Dan Glickman prepared to unveil the U.S. Plan for Food Security on Friday, and said they plan to ask U.S. aid officials to help fund an emergency monitoring and research program.

"The resurgence of stem rust in Uganda is alarming because it signals the breakdown of a resistance gene that protects wheat in many countries," said Timothy Reeves, the center's director.

Most affected would be eastern and southern Africa, where many crops depend solely on the sr-31 resistance gene.

But the sr-2 gene complex, used throughout much of the rest of the world and which is still able to prevent the fungus, may not work as effectively against the mutated spores.

The last major outbreak, which occurred in the United States in the mid-1950s, destroyed up to 50 percent of wheat crops on many U.S. farms.

Reeves said research is needed using new biotechnology methods, like molecular marking, to understand the sr-2 resistance and possibly develop more defenses against crop diseases like stem rust, leaf rust and yellow rust.

One thing is sure: The spores won't stay on the African savanna where they first appeared. "It'll move," Reeves said. "It will travel."