Scientists Tackle Aluminum Intolerance in Wheat

Borrowing genes from another plant, such as rye, may be wheat's best hope for surviving on acidic, high-aluminum soils.

That's the latest word from Agricultural Research Service scientists and their colleagues abroad who grew U.S. and Brazilian wheat varieties hydroponically to check the varieties' aluminum tolerance. They report that none of the modern wheat varieties were any better equipped to tolerate aluminum-laced soils than BH 1146, developed in Brazil more than 50 years ago.

Aluminum, found mostly just below topsoil, impairs plant growth on nearly half of the world's eight billion acres of crop land, including about 86 million acres in the United States. Lime can be added repeatedly to de-acidify soil, decreasing plants' vulnerability. But lime is expensive to transport long distances.

While wheat may be lacking in aluminum tolerance genes, those genes are present in rye, a related species that generally produces less grain. Geneticist Perry Gustafson and colleagues at ARS' Plant Genetics Research Unit in Columbia, Mo., are finding aluminum tolerance approximately equal to that of rye in some breeding lines of wheat-rye hybrids, called triticales, now being developed. Triticales, however, generally are more suitable for livestock feed than for flour.

Many modern high-yielding bread wheats have genetic resistance to diseases like powdery mildew, thanks to rye genes that may have been acquired through a triticale ancestor. Breeding in aluminum tolerance seems a greater--but doable--task.

The ARS scientists found that numerous wheat genes, lurking somewhere in various chromosomes, suppress the expression of aluminum tolerance genes from rye. Genetic sleuthing to locate the most important suppression genes might take another 10 years. When found, those genes may be replaced with genes that are more aluminum-friendly through conventional plant breeding or biotechnology.

While the world's population is growing apace, wheat yield increases have tapered. Until now, most increases have been on fertile soils. In the future, adequate production may depend increasingly on marginal soils.

Scientific contact: Perry Gustafson, Plant Genetics Research Unit, USDA, Columbia, MO 65211; Phone (573) 882-7318, fax 875-5359, pgus@showme.missouri.edu.