BIOLOGY AND BIOLOGICAL CONTROL OF ROOT DISEASES OF WHEAT, BARLEY AND BIOFUEL BRASSICAS
Location: Root Disease and Biological Control Research
Title: Structure and function of indigenous antibiotic-producing microbial communities in the rhizosphere of wheat
Submitted to: International Plant Growth Promoting Rhizobacteria Workshop
Publication Type: Abstract Only
Publication Acceptance Date: June 7, 2012
Publication Date: June 7, 2012
Citation: Mavrodi, D., Mavrodi, O., Bonsall, R., Parejko, J., Weller, D.M., Thomashow, L.S. 2012. Structure and function of indigenous antibiotic-producing microbial communities in the rhizosphere of wheat. International Plant Growth Promoting Rhizobacteria Workshop. Vol. 9, page 42.
Phenazines are among the most widely studied metabolites produced by fluorescent Pseudomonas spp., not only because of their role in biological control but also because they function in biofilm formation, redox homeostasis, mineral acquisition, and, in some cases, pathogenesis. Despite the frequency with which they have been reported as biocontrol agents, however, the distribution in nature of phenazine producers, and the quantitative and qualitative aspects of phenazine production in natural settings, are poorly understood We addressed this issue by determining the geographic distribution of indigenous phenazine-producing (Phz+) Pseudomonas populations and the amounts of phenazine-1-carboxylic acid (PCA) produced in the rhizosphere of wheat grown in dryland and irrigated fields in the low-precipitation zone (<300 mm) of the Columbia Plateau in the Inland Pacific Northwest, USA, and in adjacent, higher precipitation areas. Only Phz+ Pseudomonas spp. were detected in all sampled dryland fields, with mean population sizes ranging from log 3.2 to log 7.1 g-1 fresh weight of root. PCA was detected in the rhizospheres of plants from 26 of 29 fields sampled, and linear regression analysis demonstrated a significant (P <0.0001) relationship between the population density of Phz+ isolates and the amount of PCA recovered from the rhizosphere. Wheat grown under irrigation harbored both PCA- and 2,4-diacetylphloroglucinol (DAPG)-producing isolates, but the frequency of recovery of DAPG producers was significantly greater, consistent with the hypothesis that soil moisture is a major abiotic factor that drives the development of indigenous antibiotic-producing microbial communities.