Highly acidic soils hamper plant growth.

Increasing wheat yields at the present rates, on the world's richest soil, may not be enough to provide adequate nourishment to people in countries with rapidly growing populations, according to an Agricultural Research Service geneticist, in Columbia, MO.

The world's less productive soils also must produce much higher wheat yields to feed the world population, projected by the United Nations to hit 9 billion people in 2040, according to J. Perry Gustafson, at the ARS Plant Genetics Research Unit, in Columbia. Increasing dependence will be placed on acidic, high-aluminum soils. Aluminum, found mostly just below the topsoil, impairs plant growth on nearly 2.5 billion of the world's 8 billion acres of cropland, including 86 million U.S. acres.

When soils are acidic, more aluminum is available in the soil and plant growth is restricted. Gustafson wants to help plant breeders develop new wheat varieties with genes enabling plants to yield abundantly on this type of soil. Another way to increase yields, beside breeding, is to add lime to deacidify soils, but hauling lime long distances is expensive.

In researching ways to tap into genetic resources for improving aluminum tolerance, Gustafson and colleagues have identified a major wheat gene for aluminum tolerance, found between two closely situated marker genes. Wheat breeders now can select breeding lines that have these markers, in order to breed for aluminum tolerance. This marker-assisted selection may halve the current 10 to 15 years it takes to develop a new variety.

Also, borrowing genes from another cereal, rye, may be wheat's best hope for surviving on acidic, high-aluminum soils. The research on mapping rye genes may help breeders place desirable rye genes into wheat-rye crosses without sacrificing wheat's desirable agronomic and food qualities. Gustafson has found molecular markers in rye that are closely linked to the aluminum tolerance genes and can help transfer desirable rye genes into wheat.

ARS is the U.S. Department of Agriculture's chief scientific research agency.

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