Soybean cyst
nematode and egg. Magnified 1,000X. (Plate # 10334, courtesy ARS Electron
Microscopy Unit). Click the image for high-resolution image.
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Bacteria Tapped to Battle Crop-Damaging
Roundworms
By Jan
Suszkiw March 30, 2009
Beneficial bacteria, aided by a "cocktail" of potent natural
compounds, may offer a way to biologically control soybean cyst nematodes and
other crop-damaging roundworms. That's the implication of ongoing studies by
scientists with the Agricultural Research
Service (ARS) and the Donald
Danforth Plant Science Center (DDPSC) in St. Louis, Mo.
Petri dish tests and live-plant experiments at the St. Louis research
center showed that the bacteriamembers of the genus
Pseudomonascaused the nematodes to stop moving and, in some cases,
disintegrate.
Phenazines, hydrogen cyanide and phloroglucinols are among the
Pseudomonas compounds being examined for their biocontrol activity
against the nematodes. However, no single compound has emerged as the sole
cause of the worms demise, notes plant geneticist
Patricia
Okubara, with the
ARS
Root Disease and Biological Control Research Unit in Pullman, Wash.
Her DDPSC co-investigator, Chris Taylor, isolated the
Pseudomonads from the banks of the Missouri and Mississippi rivers,
farms and dried botanical specimens. All told, his Pseudomonas
collection totaled 63 strains. Of those, he chose 20 for their ability to
infect and kill the soybean cyst nematode (Heterodera glycines),
root-knot nematode (Meloidogyne incognita) and/or the nematode
Caenorhabditis elegans. Washington State
University nematologist Ekaterini Riga showed that four of the 20 strains
were also active against M. chitwoodi or M. hapla nematodes.
The cyst nematode is a top target of the scientists
bacteria-based approach because of the substantial losses its feeding causes to
America's $27 billion soybean crop. Treating soil with pesticides, rotating
crops and planting resistant varieties help keep the pest's numbers in check.
But chemical control is costly, crop rotation isn't always economically
feasible, and resistant varieties are eventually overcome by virulent new
biotypes of the nematode. Pseudomonads could also be used against
quarantine pests, including the potato cyst nematode, Globodera pallida,
recently found in Idaho.
According to Okubara, novel controls are needed that can be used as
part of an integrated approach, with potential benefits including improved
environment health, longer-lasting crop resistance, and reduced production
costs.
Another, longer-term approach is to engineer crop plants to produce
the nematode-neutralizing compounds themselves, adds Okubara, who began
collaborating with Taylor in 2007 under a three-year National Research
Initiative grant.
ARS is the principal intramural scientific research agency of the
U.S. Department of Agriculture.