NEWS for North Dakotans
Agriculture Communication, North Dakota State University
7 Morrill Hall, Fargo, ND 58105-5665

March 25, 1999

NDSU Wheat Plot No. 2 a `National Treasure'

Motorists driving on Fargo's 18^th Street North, along where it cuts through the North Dakota State University campus, probably aren't reminded of Yellowstone National Park. But to researchers on the lookout for naturally occurring organisms to control plant diseases, NDSU's Wheat Plot No. 2 and Yellowstone have a great deal in common.

"When Yellowstone National Park was established, who would have thought that it would become one of the hottest biological resources in the world? The site at Fargo has similar-type value. Basically, the NDSU Wheat Plot No. 2 is a national treasure," says David Weller, a plant pathologist with USDA's Agricultural Research Service at the Root Disease and Biological Control Research Unit in Pullman, Wash.

Every year since 1882 Wheat Plot No. 2 has produced hard red spring wheat, says Al Schneiter, chair of the Department of Plant Sciences at NDSU. As a result of this century-plus cropping history, Wheat Plot No. 2 has become the oldest continuous spring wheat plot in the world. The plot, along with NDSU's Flax Plot No. 30, gained entry into the National Register of Historic Places in 1992.

Today, the primary function of Wheat Plot No. 2 continues as always--to aid plant breeding efforts, says Robert Stack, an NDSU plant pathologist who has used the plot to test experimental hard red spring wheat lines for resistance to common root rot.

Stack credits NDSU's first plant pathologist, H.L. Bolley, with having the foresight to keep Wheat Plot No. 2 in continuous wheat. Using that plot and others, Bolley was able to show that Red River Valley soils weren't "worn out," as was the common belief during the early part of this century. Rather, Bolley discovered that the soils were suffering from a build-up of several types of disease, and he used these plots, his "disease gardens," to demonstrate that crop rotation and clean seed could reduce disease and make valley soils productive once again.

But not all root diseases continue to build up in soils under continuous cropping systems (monocultures), Stack says. Earlier this century, U.S. and European researchers discovered that severe outbreaks of a root-destroying fungal disease known as take-all would eventually be controlled--naturally. They called this phenomenon take-all decline, but they didn't know what caused it.

"Wheat Plot No. 2 has had this natural control of take-all for decades. The bacteria are well established in the plot," Stack says. He adds, "It would take another 100 years to reproduce the microbiological makeup of the plot."

By the 1970s, researchers knew that a genus of bacteria (Pseudomonas) played a role in take-all decline, but they didn't know how. In the 1980s, a USDA-ARS research team from Washington state proved that some bacterial strains produced substances which suppressed take-all. They also successfully transferred the ability to produce these substances to other strains. Besides Weller, the other scientists on this team were NDSU alum Jim Cook, USDA's senior plant pathologist at the time, and ARS geneticist Linda Thomashow.

Based on research conducted this decade involving long-term wheat soils from Quincy, Wash., Weller and his ARS colleagues have found that only one bacterial substance, Phl (2,4-diacetylpholorglucinol), suppresses take-all. They also have found that this substance is produced by a number of "premier" bacterial strains.

Weller says what makes these strains special are two unique qualities: one, the strains establish quickly in wheat roots, and two, low numbers of bacteria control take-all disease effectively. And unlike other bacteria, the populations of the premier strains decline much less from competition with other organisms.

In 1997, Weller traveled throughout the United States and collected soil samples from continuously cropped wheat plots, including NDSU's Wheat Plot No. 2. He says, "As our hypothesis predicted, the Fargo soil is loaded with bacteria that produce Phl, and that soil's producers of Phl look similar to the ones coming from the Washington soils."

ARS has applied for a patent on the premier bacterial strains that Weller's group has identified in the Washington soils, along with the genetic "fingerprint" and the methods for finding similar strains in other soils. Two companies plan to license the technology to produce seed treatments or other biological controls using the bacteria from Washington soils. Weller expects products to be available within a couple of years and says it's possible to control take-all on as many as 1,000 acres with only a quart of the bacterial culture.

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Sources: Al Schneiter (701) 231-8137 and Robert Stack (701) 231-7077

Editor: Dean Hulse (701) 231-6136