Scientists Corn Seed Gets Microbial
Coat Against Harmful Fungi
By Jan Suszkiw
BELTSVILLE, Md., Jan. 23--Harmful fungi that try to invade newly
sprouted corn seeds may be kept at bay by a new tactic of
U.S. Department of Agriculture scientists:
seeds coated with helpful microbes that weaken or kill the would-be fungal
Weve devised a procedure that uses naturally occurring,
beneficial fungi and bacteria to protect corn seed from disease caused by the
fungal plant pathogens Pythium and Fusarium, said plant
pathologist Robert Lumsden of USDAs Agricultural Research Service in
Unchecked, Pythium and Fusarium cause rot diseases that can
reduce corn yields 10 to 30 percent, said Lumsden at ARS Beltsville
Agricultural Research Center (BARC).
The fungi are scourges of corn crops throughout the U.S., particularly in the
Midwest, he said.
Enlisting multiple species of beneficial microorganisms is a new form
of biological control, Lumsden said. In the past, the approach has
been to use one biocontrol agent against one plant pathogen. But this
wont guard against other disease-causing organisms that may also be in
the soil, he explained.
So, the scientists coated seed with a combination of helpful bacteria and
fungi they isolated from plant roots and surrounding soil. These
microorganisms attack pathogens in a number of ways, Lumsden said.
They compete with fungal pathogens for nutrients; they make antibiotics
that kill or repel the pathogens, or they serve as parasites that invade and
consume the pathogens from within.
And, compared to chemical fungicides, he said, the beneficial
microorganisms pose no environmental hazard and protect plants at least as well
Lumsden, research leader of the
Biocontrol of Plant
Diseases Laboratory, led a scientific team that includes soil scientist
Jack Lewis, plant pathologist Weili Mao and microbiologists Daniel P. Roberts,
Prakash Hebbar and Shin-I Chow. They conducted lab and field tests at the
The scientists also ran tests in Minnesota, Delaware and Virginia, to learn
how microbe-coated seed would fare against the harmful fungi in various soils,
climates and other conditions. Collaborators included scientists at the
University of Delaware in Newark,
Virginia Polytechnic Institute and State
University in Blacksburg, and a commercial firm.
Pythium flourishes when soils are cool and wet, such as during the
spring. It causes damping-off, a rot disease of seeds and seedlings.
Fusarium prefers warm, dry conditions typical of summer. It attacks the
roots of corn plants. In one field study, only about half the seeds sprouted
and grew to mature plants in plots harboring both fungi.
But in plots where seeds were coated with a combination of beneficial fungi
and bacteria, more than 80 percent became full-grown plants. This bettered or
equaled the performance of seed protected with coatings of any of several
fungicides, said Beltsville researcher Jack Lewis.
Protection by the good microbes continues after the seedling stage. Mature
plants in the biocontrol plots had about 25 to 40 percent less damage from root
and stalk rot diseases, compared to plants grown from untreated seed, Lewis
In their approach, Lumsdens team uses fermentation to brew
large amounts of beneficial microbes. Then they formulate the microbes into a
mix that can be coated onto the seed.
Lumsden envisions that soybeans, dry beans and some other high-value crops
could also benefit from the seed treatment.
Scientific contact: Robert Lumsden, research leader, Biocontrol of
Plant Diseases Laboratory, Bldg. 011A, Beltsville, Md. 20705. Telephone (301)