Role of 2,4-Diacetylphloroglucinol-Producing Fluorescent Pseudomonas spp. in the Defense of Plant Roots

D. M. Weller; B. B. Landa; O. V. Mavrodi; K. L. Schroeder; L. De La Fuente; S. Blouin Bankhead; R. Allende Molar; R. F. Bonsall; D. V. Mavrodi; L. S. Thomashow

doi:10.1055/s-2006-924473

Plant Biology, Inhaltsverzeichnis

Plant Biol (Stuttg) 2007; 9(1): 4-20
DOI: 10.1055/s-2006-924473

Review Article

Georg Thieme Verlag Stuttgart KG · New York

Role of 2,4-Diacetylphloroglucinol-Producing Fluorescent Pseudomonas spp. in the Defense of Plant Roots

D. M. Weller¹ , B. B. Landa² , O. V. Mavrodi³ , K. L. Schroeder³ , L. De La Fuente³ , S. Blouin Bankhead³ , R. Allende Molar³ , R. F. Bonsall³ , D. V. Mavrodi³ , L. S. Thomashow¹

¹USDA‐ARS Root Disease and Biological Control Research Unit, Washington State University, P.O. Box 646430, 367 Johnson Hall, Pullman, WA 99164-6430, USA
²Departamento de Agronomia, Universitad de Córdoba, Apdo. 3084, 14080 Córdoba, Spain
³Department of Plant Pathology, Washington State University, P.O. Box 646430, Pullman, WA 99164-6430, USA

Abstract

Plants have evolved strategies of stimulating and supporting specific groups of antagonistic microorganisms in the rhizosphere as a defense against diseases caused by soilborne plant pathogens owing to a lack of genetic resistance to some of the most common and widespread soilborne pathogens. Some of the best examples of natural microbial defense of plant roots occur in disease suppressive soils. Soil suppressiveness against many different diseases has been described. Take-all is an important root disease of wheat, and soils become suppressive to take-all when wheat or barley is grown continuously in a field following a disease outbreak; this phenomenon is known as take-all decline (TAD). In Washington State, USA and The Netherlands, TAD results from the enrichment during monoculture of populations of 2,4-diacetylphloroglucinol (2,4-DAPG)-producing Pseudomonas fluorescens to a density of 10⁵ CFU/g of root, the threshold required to suppress the take-all pathogen, Gaeumannomyces graminis var. tritici. 2,4-DAPG-producing P. fluorescens also are enriched by monoculture of other crops such as pea and flax, and evidence is accumulating that 2,4-DAPG producers contribute to the defense of plant roots in many different agroecosystems. At this time, 22 distinct genotypes of 2,4-DAPG producers (designated A - T, PfY and PfZ) have been defined by whole-cell repetitive sequence-based (rep)-PCR analysis, restriction fragment length polymorphism (RFLP) analysis of phlD, and phylogenetic analysis of phlD, but the number of genotypes is expected to increase. The genotype of an isolate is predictive of its rhizosphere competence on wheat and pea. Multiple genotypes often occur in a single soil and the crop species grown modulates the outcome of the competition among these genotypes in the rhizosphere. 2,4-DAPG producers are highly effective biocontrol agents against a variety of plant diseases and ideally suited for serving as vectors for expressing other biocontrol traits in the rhizosphere.

Key words

Antibiotics - biological control - rhizobacteria - suppressive soil - take-all

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D. M. Weller

USDA‐ARS Root Disease and Biological Control Research Unit
Washington State University

P.O. Box 646430

367 Johnson Hall

Pullman, WA 99164-6430

USA

eMail: wellerd@wsu.edu

Review Editor: J. Raven