Forum -- Getting to the Root of Wheat
I'll never forget walking into the laboratory one Monday in April 1970.
The table was covered with clear plastic bags of green wheat from a field
experiment near Puyallup, Washington. Plants in four bags had white, healthy
roots. Plants in the other 32 bags had black, dead roots.
The experiment site was heavily infested with the fungus that causes the
wheat root disease called take-all. The plants with white roots were from four
plots with special soil.
In 1968, we had mixed into the native soil a small amount of soil from a
wheat field in Quincy, about 150 miles east of Puyallup. The soil came from a
field where take-all was being controlled naturally and mysteriouslya
process reported a few years earlier in Europe as "take-all decline".
I knew there was something in the Quincy soil so powerful that it kept roots
white when they should have been black. I also figured that the protective
factor in the soil could multiply on wheat roots. If I did nothing else for the
rest of my career, I was going to find out what was in that soil.
We have since learned that natural bacteria, selectively favored by wheat
roots, produce antibiotics that suppress take-all. Now advances in fermentation
technology are helping to create a commercial seed treatment that will soon be
available to fanners.
A story in this issue [p. 4] describes our success in isolating the
microorganisms that produce the antibiotics and using them to control take-all.
We're also enhancing the bacteria's natural antibiotic production with genetic
techniques. And we have molecular methods to measure the frequency of these
antibiotic-producing strains' occurrence in soil.
Disease control is important because wheat with root diseases not only
yields poorly, it also leaves nitrogen fertilizer unused in the soil, is less
competitive with weeds, and does not take full advantage of available water
In addition, root diseases make it more difficult for farmers to adopt
erosion-controlling practices such as no-till and minimum-till.
The very conditions needed to hold soil in placelittle or no soil
disturbance from tillage and standing plant stubble from the previous
cropprovide the perfect environment for take-all and other root diseases
like Rhizoctonia and Pythium to thrive.
Another research program at Pullman, called STEEP, successfully tackles the
many issues and technical problems associated with conservation tillage
The take-all and STEEP research share two approaches that help account for
First, both use nature as a guide to solve real-world problems.
Take-all decline was observed in nature years before basic research revealed
how it worked and how to take advantage of the beneficial organisms
responsible. Our results can be translated into field applications because the
work started in the field.
STEEP researchers realized that soil eroded differently in the Northwest
than in other areas of the country. Field tests and observations allowed them
to modify the Universal Soil Loss Equation developed by ARS in 1958. It now
gives land managers an accurate tool to predict erosion for this unique area.
Second, both programs rely on grower participation.
Our ability to commercialize a biological control for take-all is fueled by
farmers who have seen their yields declineeven while increasing
fertilizer. We're providing the technology, and they're conducting large-scale
testing on their farms.
STEEP has more formalized grower input, along with an advisory committee, an
on- farm testing program, and follow-up surveys.
Solutions to the problems of conservation farming systems have come slowly,
and there are still more questions than answers. Nevertheless, the goals of
STEEP and of our work on biological control of take-all are clear: more
economical farming, a cleaner environment, and protection of the natural
resource base upon which agriculture depends.
R. James Cook
Agricultural Research Service