David Schisler examines two wheat seed heads inoculated with the causal agent
of head blight, also known as head scab. The seed head on the right was sprayed
with biocontrol microbes that greatly reduced disease symptoms. Click the
image for more information about it.
USDA Patents Microbes to Fight Wheat Fungus
Suszkiw July 17, 2006
Four yeasts and three bacteria that live on flowering wheat heads, but
cause no harm there, have been patented by the U.S. Department of Agriculture
(USDA) as biological control agents in the
fight against Fusarium head blight (FHB).
Caused by the fungus Fusarium graminearum, FHB is among the
most costly diseases of cereal crops worldwide, including wheat, barley and
oats. From 1998 to 2000, FHB epidemics in U.S. small grains inflicted an
estimated $2.7 billion worth of losses, notes
Schisler. He is a plant pathologist with the Agricultural Research Service
(ARS), USDA's chief scientific research
The fungus infects wheat through its flower tissues, including
anthers. But competition for space and nutrients there is fierce, according to
studies by Schisler and colleagues at the ARS
Center for Agricultural Utilization Research in Peoria, Ill., and at Ohio
State University (OSU) in Columbus. Indeed,
some of the bacteria and yeasts that the researchers isolated from wheat
anthers secrete antibiotics, or use other means, to keep the fungus at bay--to
the wheat plant's benefit.
To exploit this "natural antagonism," Schisler and OSU colleagues
Michael Boehm and Naseem Khan devised fermentation procedures to culture
quantities of the beneficial microbes for application to flowering wheat heads.
The four yeasts and three bacteria that have been patented (U.S. No. 7,001,755)
were the "top picks" from about 700 microbial specimens the scientists
evaluated for their fungus-fighting prowess. Of these seven, yeast strain OH
182.9 performed the best in field trials, reducing FHB's severity in spring,
winter and durum wheats by 20 to 60 percent.
USDA's patenting of this approach to controlling FHB is a critical
first step towards garnering the commercial interest necessary to develop the
microbes as registered biological control products that can be used separately
or in specific combinations on wheat or other cereal crops. Their development,
along with more FHB-resistant wheat varieties, is especially appealing because
the use of foliar fungicides is complicated by timing and availability by