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Unraveling the Genome of an Alfalfa Relative

By Don Comis
February 11, 2002

The National Science Foundation has awarded a $1.5-million, four-year grant to scientists with the Agricultural Research Service, universities and the Nobel Foundation to further unravel the genome of barrel medic, Medicago truncatula. This is a close relative of one of the world’s top forage crops, Medicago sativa, better known as alfalfa.

Plant pathologist Deborah A. Samac and plant physiologist Carroll P. Vance at the ARS Plant Science Unit, St. Paul, Minn., are working collaboratively on the genome project with scientists at the University of California at Davis, the University of Minnesota and the Nobel Foundation.

The work may eventually help the scientists find genes that will make alfalfa an even more profitable crop and one better suited for new uses such as production of ethanol fuel.

The grant is a continuation of an earlier NSF grant that funded work in which Samac, Vance and colleagues showed that most of the mapped genes for barrel medic and alfalfa are found in the same location on each species’ genome. That earlier work also showed that many genetic markers for barrel medic can be used to find genes in alfalfa. In those studies, the scientists identified about one-third of the 30,000 genes that are thought to be in barrel medic’s genome.

Samac and Vance are particularly interested in finding genes that would give the plant improved resistance to diseases and also enhance it’s ability to “fix” nitrogen, a process in which plants can take nitrogen from the atmosphere and change it into a form they can use as natural fertilizer to stimulate their own growth.

New genetic techniques are making it possible for scientists to compare thousands of genes at one time and to see which ones turn on or off in the presence of friend or foe-- for example, disease or beneficial organisms, such as the microbes that “fix” nitrogen inside of plant roots. In the past, this type of study could only be done for a few genes at a time. The new techniques should speed up researchers’ chances of finding genes that have roles in more than one function. The scientists will research whether the identification tags developed for barrel medic’s genes will help them find similar or identical genes in alfalfa.

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

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