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Title: Control of cereal root pathogens with PGPR: The role of the natural antibiotic phenazine-1-carboxylic acid

item Thomashow, Linda
item Weller, David
item MAVRODI, DMITRI - University Of Southern Mississippi
item MAVRODI, OLGA - Washington State University
item PAREJKO, J. - University Of Wisconsin
item LE TOURNEAU, MELISSA - Washington State University
item BONSALL, ROBERT - Washington State University

Submitted to: International PGPR Workshop
Publication Type: Abstract Only
Publication Acceptance Date: 4/1/2015
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Root pathogens are major agricultural impediments worldwide and must be controlled on the same or less arable land than currently available in order to meet the needs of the rapidly growing world population. In the Pacific Northwest (PNW) of the USA, where wheat is grown across a wide range of climatic conditions, the natural antibiotics phenazine-1-carboxylic acid (PCA) and 2,4-diacetylphloroglucinol (DAPG) are produced in the rhizosphere by indigenous PGPR and provide protection against fungal root pathogens. The geographic distribution of these bacterial groups is largely determined by soil moisture, with phenazine-producing strains (Phz+) localized to the roots of wheat grown within the low precipitation zone (<300 mm annual rainfall) and DAPG producers associated with wheat in higher precipitation areas and fields under irrigation. Included among producers of PCA are the model strain 2-79 and representatives of three other Pseudomonas species that comprise up to 10% of the culturable rhizobacteria. PCA production on roots of dryland wheat occurred mainly during the first half of the growing season but remained detectable for at least 130 days. In vitro, the compound persisted with a half-life of 3 or 4 days in dry or moist soils, respectively, and remained detectable throughout a period of 20 days. These data indicate that most PCA synthesis in the field occurs early in the season, but suggest that synthesis continues even as soil water potentials approach as low as -400 to -500 kPa. We suggest that PCA producers survive desiccation on roots in biofilms. PCA influenced biofilm formation by some, but not all, Phz+ strains and its impact varied with matric or osmotic stress levels. Structural differences also were observed in colony biofilms grown from strains of different species under control and stress conditions, and distinct differences were observed between some wild-type Phz+ strains and their Phz- mutants.