By Jan Suszkiw
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
David 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
pinch?economically speaking?when such fungal breaches lead to shriveled,
chalky-white kernels, notes Schisler, in the ARS 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 fungus.

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 63 percent.

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.

Read more about the research in the April 2008 issue of Agricultural
Research magazine.

ARS is the U.S. Department of Agriculture's chief scientific research
agency.


[www.ars.usda.gov]