By Jan Suszkiw


Using biotechnology, Agricultural Research Service (ARS) scientists have
fortified the defenses of soybean plants against tiny but destructive pests
called soybean cyst nematodes (SCN).


The wormlike pests live in the soil, where they can wriggle into soybean
roots to feed, mate and lay eggs. The damage they cause to root cells
obstructs the flow of nutrients and water to the rest of the plant,
weakening it.

Such attacks cost U.S. soybean farmers up to $1 billion in losses annually.
Although SCN-resistant soy varieties are available, the nematodes can
eventually overcome the resistance by evolving into virulent new races.
Fumigating soils before planting can diminish the pest's numbers, but such
chemical control is costly.

As an alternative, ARS plant physiologist Ben Matthews and colleagues in
Beltsville, Md., are exploring the use of genetic engineering to bolster SCN
resistance in soybeans using novel or existing genes.

Earlier this year, for example, Matthews' team completed greenhouse trials
of soybean plants whose roots had been engineered with a DNA copy of one of
the nematode's own protein-making genes. When nematodes ingest the DNA copy,
the DNA "deactivates" the expression of the pest's corresponding gene, so it
stops making the protein.

In greenhouse trials at the ARS Soybean Genomics and Improvement Laboratory
in Beltsville, 80 to 90 percent of juvenile female nematodes that fed on the
engineered soybean roots died or failed to mature by 30 days.

Matthews' team, together with a Towson University bioinformatics expert,
used comparative genomics and genome sequence information from another
nematode species, Caenorhabditis elegans, to identify the SCN protein gene
they targeted.

According to Matthews, a second round of greenhouse studies is planned to
confirm the initial results. Similar studies with other
resistance-conferring genes are under way.

Commercial soybeans derived from the team's research are at least eight
years away. That's contingent upon successful field tests, further
refinement, regulatory approval, propagation and other requirements, notes
Matthews.

ARS is a scientific research agency of the U.S. Department of Agriculture.
www.chechbiotech.org