A Cold Approach to Nematode Egg-Hatch
By Luis Pons
February 28, 2007
The egg-hatch characteristics of
soybean cyst nematodes, especially after exposure to cold, might hold clues
that could one day help keep them under control, according to Agricultural
Research Service (ARS) scientists in
Soybean cyst nematodes, Heterodera glycines, are microscopic
roundworms in the soil that cost U.S. farmers hundreds of millions of dollars
in losses each year.
Masler and plant pathologist
Zasada, in the
Nematology Laboratory at Beltsville, have studied the conditions under
which this pest's eggs hatch. They've found that the eggs fall into two
categories: those that readily hatch in water, and those that will hatch only
when exposed to a host plant.
In follow-up research, Masler and Zasada discovered that duration of
exposure to cold decreases the number of soybean cyst nematode eggs that will
later hatch in water.
In one study, 70 percent of H. glycines eggs readily hatched in
81° F water over 12 days, while others hatched only when exposed to
soybean plants. The scientists then stored eggs in water refrigerated to
41° F for varying lengths of time, and found that refrigeration suppressed
hatch but didn't kill the eggs.
Although refrigerated eggs ultimately hatched when returned to 81° F
water, the length of refrigeration time affected the number of eggs that would
hatch in water. That rate dropped to 30 percent after two weeks of
refrigeration, 20 percent after four weeks, and to less than 10 percent after
The results indicate that if nematode embryo development is stopped before
reaching a critical developmental stage, it can resume only after the embryo is
exposed to additional stimulisuch as from a host plantand returned
to normal temperature.
According to Masler, refrigeration holds potential as a means of producing
H. glycines eggs of different developmental stages. These would be
useful in studying molecules related to hatching and other regulatory functions
that may be exploited for biological control of the pest.
ARS is the U.S. Department of
Agriculture's chief scientific research agency.