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ARS technician Kathleen Ross and
graduate students Miguel Rodriguez
(left) and Miftahudin analyze an
amplified fragment length polymorphism
film as they search for molecular
markers linked to genes controlling
aluminum tolerance in wheat and rye.
(K9721-2)
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To increase wheat yields at the
present rate on the world's richest soils may not be enough to help provide
adequate nourishment for countries whose populations are growing rapidly, muses
ARS geneticist J. Perry Gustafson. The
world's less-productive soils must also produce much higher wheat yields to
feed the 9 billion people the United Nations projects will inhabit the globe in
2040.
"We'll have to depend increasingly on acidic, high-aluminum soils,"
Gustafson says. Aluminum, found mostly just below topsoil, impairs plant growth
on nearly 2.5 billion of the world's 8 billion acres of cropland, including
about 86 million acres in the United States.
When soils are acidic, more aluminum is available to restrict wheat growth. One
of Gustafson's passions is to help plant breeders develop new wheat varieties
with genes that enable the plant to yield abundantly on this type of soil.
Besides breeding, another way to increase yields is to add lime to deacidify
the soil. But lime is expensive to transport long distances.
At ARS' Plant Genetics Research Unit, in Columbia, Missouri, Gustafson
researches ways to tap into genetic resources for improving aluminum tolerance
in wheat. He and his colleagues have mapped the location of a major wheat gene
for aluminum tolerance found between two closely situated marker genes. Wheat
breeders can now select breeding lines that have these markers in order to
breed for aluminum tolerance. This process, called marker-assisted selection,
may halve the 10 to 15 years it currently takes to develop a new variety.
The Brazilian wheat, called BH 1146, in which the marker was identified was
developed more than 50 years ago and so far has no equal for aluminum
tolerance.
Borrowing genes from another cereal—rye—may be wheat's best hope for
surviving on acidic, high-aluminum soils, Gustafson says. His research on
mapping genes in rye may help breeders make sure they place desirable rye genes
into wheat-rye crosses without greatly sacrificing wheat's desirable agronomic
and food qualities. He's found molecular markers in rye that are closely linked
to the aluminum-tolerance genes and can be used to help transfer desirable rye
genes into wheat.
Thanks to research done on wheat-rye crosses many decades ago, most of the
modern high-yielding bread wheats have rye genes that impart resistance to
diseases like powdery mildew. Other rye genes are suppressed. Breeding for
aluminum tolerance in the same fashion has until now been a more daunting task,
because lurking somewhere in various wheat chromosomes are certain genes that
suppress the expression of rye aluminum-tolerance genes.
Through further genetic sleuthing, Gustafson and his colleagues hope to locate
the most important suppression genes and then figure out how to delete
them.—By Ben Hardin, formerly with ARS.
The research is part of Plant, Microbial, and Insect Genetic Resources,
Genomics, and Genetic Improvement, an ARS National Program (#301) described on
the World Wide Web at http://www.nps.ars.usda.gov.
J. Perry Gustafson is in the
USDA-ARS Plant
Genetics Research Unit, Room 206, Curtis Hall, University of Missouri,
Columbia, MO 65211; phone (573) 882-7318, fax (573) 875-5359. |
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