Race 15B

In the Imperial Valley of California last week, twelve acres of assorted wheat plants were growing in the hot desert sun. Department of Agriculture scientists, tending them as carefully as premature babies, hope that one or more of the 600 varieties now being tested will overcome "Race 15B," the new strain of black stem rust that is seriously threatening the U.S. wheat crop.

Wheat rust has been around a long time. It bothered Roman wheat growers so much that they created a special rust god, Robigus, and blamed him for its outbreaks. U.S. plant scientists thought they had licked it. They bred rustproof wheat varieties that kept U.S. fields almost clear of the disease for 15 years, accounting for a good part of recent bumper wheat crops. Last summer Race 15B, a new, extra-virulent strain, appeared on wheat from Pennsylvania to Texas. It attacked all commercial varieties. Durum wheat, used for making spaghetti, was hardest hit, with 10 million bushels lost.

Last summer's losses are nothing to what might happen next summer. Rust is a quick-growing fungus that spreads by microscopic spores carried on the wind. "The spores," says Agriculture, "migrate like wild birds." North winds blow them south in fall, where they spend the mild winter on wheat in Texas and Mexico. When the weather gets warmer, they are blown back to the wheat belt by southerly winds.

Rust has another way of wintering. When the weather begins to get cold in the north, the fungus produces black, cold-proof spores. These spend the winter on straw or stubble. In spring, they germinate, sending out small spores that infect barberry bushes. Up to 70 billion vigorous spores can form on an average barberry bush. Each spore can start a fast-spreading infection in a stand of wheat.

One way to fight rust is to eradicate barberry bushes in the wheat belt. Another is to hope that the weather will not be favorable for the fungus wintering in Texas. The Department of Agriculture, after taking a horrified look at the Race 156 situation, trusts neither of these methods. It is trying to breed wheat that can resist. By growing its new varieties in winter in the Imperial Valley, it gets two generations a year, speeds up the development process.

Already some varieties look good. In May their seed will be harvested and planted again in states where spring wheat is normally grown; then back to California for another winter growing season. Not for another four or five years will U.S. farmers have a wheat variety that is proof against Race 15B. Until then, Government scientists can only hope for the best.

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