ECOLOGY OF PHLOROGLUCINOL-PRODUCING PSEUDOMONADS IN TAKE-ALL SUPPRESSIVE SOILS

Recipient Organization
AGRICULTURAL RESEARCH SERVICE
(N/A)
PULLMAN,WA 99164

Performing Department
(N/A)

Non Technical Summary
(N/A)

Animal Health Component

20%

Research Effort Categories

Basic

80%

Applied

20%

Developmental

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
215	1543	1040	20%
215	1543	1100	10%
215	1543	1102	10%
215	1543	1160	20%
215	1550	1040	10%
215	1550	1100	10%
215	1550	1102	10%
215	1550	1160	10%

Knowledge Area
215 - Biological Control of Pests Affecting Plants;

Subject Of Investigation
1550 - Barley; 1543 - Soft white wheat;

Field Of Science
1040 - Molecular biology; 1160 - Pathology; 1100 - Bacteriology; 1102 - Mycology;

Goals / Objectives
Our goal is to study the ecology of 2,4-diacetylphloroglucinol (DAPG) producing pseudomonads, which are responsible for take-all decline, a natural biocontrol of take-all of wheat. Specific objectives are to evaluate the relationship between DAPG producer genotype, and root colonizing and biocontrol ability; to determine whether nonsuppressive fields can be converted to a suppressive state by introducing DAPG producers; and to determine the impact of other rhizosphere bacteria on DAPG producers.

Project Methods
Our research will test the hypothesis that there is a relationship between DAPG producer genotype, root colonizing ability and biocontrol activity. DAPG producers from each BOX-PCR genotypic group will be applied to wheat seeds and the seed then sown in the greenhouse and field. The amount of root colonization and take-all suppression for each genotype will be determined. Representatives of the most effective genotypes will be introduced into a take-all conducive field in an attempt to convert the field into a suppressive state more rapidly than occurs with natural takeall decline. In an attempt to define other microbial taxa that interact with DAPG producers, we will use terminal restriction fragment length polymorphisms (T-RFLP) to rapidly identify microbial populations and diversity associated with wheat roots from take-all suppressive and nonsuppressive soils.Formerly 5438-22000-004-07T (8/00) 5348-22000-008-07T (10/03).

Progress 08/01/00 to 07/31/04

Outputs
4. What were the most significant accomplishments this past year? 4D. Progress Report. This report serves to document research conducted under a Trust between ARS and USDA National Research Initiative, Competitive Grants Program. Additional details of the research can be found in the report for the parent project 5248-22000-012-00D, Plant Disease Research. Take-all is the most important root disease of wheat worldwide, and in the U.S. is responsible for losses in wheat production of over $1 billion annually. Take-all decline is a natural biological control of take-all and develops when wheat is grown in a field for 4-5 years continuously following a severe outbreak of the disease. Take-all remains suppressed in the field as long as wheat is grown. Take-all decline results from the build up of strains of fluorescent Pseudomonas spp., which produce the antifungal, biocontrol metabolite 2,4-diacetylphloroglucinol (DAPG). ARS scientists at Pullman, WA used molecular fingerprinting methods to distinguish 17 distinct genotypes among DAPG producers. One single genotype was shown to be primarily responsible for the natural suppressiveness of take-all decline soils in Washington State. Strains of this genotype show an unusually ability to survive and re-colonize roots of wheat the following year, which is consistent with there role in take-all decline. This research has demonstrated that it is possible to introduce this genotype into a field in the first year of wheat monoculture and thus avoid the 3-4 years of severe take-all now needed for take-all decline to develop.

Impacts
(N/A)

Publications