Research Spells Trouble for Soybean Nematodes
By Jan Suszkiw
April 18, 2001
Equipped with computer imaging, DNA
slides and a robotic arm, Agricultural
Research Service scientists are closing in on soybean genes that could
improve the legumes resistance to soybean cyst nematodes (SCN).
ARS plant physiologist Benjamin Matthews credits the microarray
technology with granting his lab a first-ever look at thousands of soybean
genes working in concert to mobilize the plants defenses against SCN
attacks. One interest, for example, is tying gene activity to a biochemical
process--the phenylopropanoid pathway--that produces lignin, a substance that
some resistant soybeans may use to cordon off SCN feeding sites, called
Currently, few commercially grown soybean cultivars resist all 14 known SCN
races, which cause $1 billion in annual losses. Eventually, plant breeders may
be able to use genes identified from microarray studies to develop new
cultivars that have broader resistance to these races, according to Matthews,
at ARSs Soybean Genomics and Improvement Laboratory, Beltsville,
There, his team is using the microarray to screen 1200 genes from six
different soybeans for activity against SCN. In the lab, a robotic arm prints
soybean DNA as tiny spots on a glass slide. Each spot is a DNA fragment
harboring one gene.
Next, the slides are bathed with fluorescent probes made of complementary
material called messenger RNA (mRNA). The mRNA comes from the roots of plants
attacked by nematodes, and from nematode-free plants.
Applied to the slides, the mRNA probes bind only to matching genes,
illuminating them when exposed to laser light. Computer software calculates the
degree to which these genes fluoresce so that scientists can see differences
among all 1,200 genes in both nematode-free and nematode-challenged plants.
A medical research speaker at a San Francisco meeting two years ago inspired
Matthews to adapt the microarray to his soybean studies, some of which the
United Soybean Board now funds.
ARS is the U.S. Department of
Agricultures principal scientific research agency.
Scientific contact: Benjamin Matthews, ARS
Alfalfa Research Lab, Beltsville, Md., phone (301) 504-5730, fax (301)