Technology Spurs Alfalfa Genome Mapping
ARS News Service
Agricultural Research Service, USDA
Jan Suszkiw, (301) 504-1630, firstname.lastname@example.org
August 2, 1999
Using computer technology to magnify light microscope images, scientists are
getting the closest look yet at the chromosome housing for alfalfa's genes.
The advance opens the door to genome mapping of alfalfa's 32 chromosomes for
traits like winter hardiness, stand persistence, and resistance to pests
like potato leaf hoppers.
Alfalfa is among America's most widely grown crops, generating over $6
billion annually, primarily as hay. Yet compared to corn or soybeans, less
is known about its complex genetic make-up, slowing breeding efforts. Over
the past 30 years, for example, alfalfa's average yield has only increased
by about one percent.
Part of the problem also stems from the fact that alfalfa plants are
autotetraploid, meaning their traits are governed by genes residing on four
chromosomes instead of two. The legume's chromosomes are also hard to
distinguish, and barely visible under a microscope.
Or so it was until scientists Gary Bauchan and Azhar Hossain tackled the
problem. With help from a Maryland firm, Loats Associates, they attached a
light microscope to a computer imaging system at their Beltsville, Md.,
Soybean and Alfalfa Research Lab, operated by the Agricultural Research
Service, USDA's chief scientific agency.
The result: a 10,000-fold increase in magnification, use of false-color, and
the precise identification and measurement of the chromosomes' length--key
to karyotyping, or arranging them from largest to smallest.
Along the chromosomes' "arms," scientists observed thick bands of
heterochromatin, material composed of DNA and protein. Like chromosomal
roadblocks, the bands can impede the exchange of genes during breeding. One
hope is that falcata alfalfas, which contain relatively few heterochromatin
bands, will help breeders introduce new traits from wild species to domestic
cultivars, broadening their genetic base.
A longer story about the advance appears in this month's issue of
"Agricultural Research," an ARS publication also on the Web at:
Scientific contact: Gary Bauchan, ARS Soybean and Alfalfa Research
Laboratory, Beltsville, Md., phone (301) 504-6649, fax (301) 504-5169,
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