Scientists Pit Bacteria against Fungi to Protect
Por Jan Suszkiw
April 3, 2008
Beneficial flower-dwelling bacteria
could soon join the fight against Fusarium graminearum, the fungus that
causes Fusarium head blight disease ("scab") in wheat, barley and
other cereal crops.
According to Agricultural Research Service (ARS) plant pathologist
Schisler, the naturally occurring bacteria may compete with F.
graminearum for nutrients exuded by the wheat plant's anthers.
One such nutrient, choline, is rich in carbon that both the bacteria and
fungus need to grow. F. graminearum also appears to rely on choline as a
chemical cue to send a germ tube into the anthers' tissues. Farmers feel the
pincheconomically speakingwhen such fungal breaches lead to
shriveled, chalky-white kernels, notes Schisler, in the
Crop Bioprotection Research Unit at Peoria, Ill. The beneficial bacteria
cause no such harm to wheat and aren't considered a danger to consumers.
In greenhouse studies and field tests, Schisler and
Ohio State University plant pathologist Mike
Boehm augmented wheat's natural community of the beneficial bacteria, using
laboratory cultures, after the crop began flowering. This gave the bacteria an
edge in consuming the choline, so less of the nutrient was available to cue the
In tests, spraying formulations of the beneficial bacteria on plots of two
commercial wheat cultivars reduced the severity of scab disease by as much as
A Pseudomonas species dubbed AS 64.4 was the best all-around
performer out of 123 choline-metabolizing (CM) bacterial strains the
researchers originally isolated from wheat anthers and examined in the
laboratory for scab suppression activity.
Ultimately, the CM strains could join other scab-fighting microbes
Schisler's group has studied, including yeasts and antibiotic-secreting
bacteria. Schisler envisions combining them in a biopesticide formulation that
farmers could spray onto wheat as added insurance against scab.
more about the research in the April 2008 issue of Agricultural
ARS is the U.S. Department of
Agriculture's chief scientific research agency.