Title: Antibiotic-producing pseudomonads in dryland wheat: from genes to ecosystem and back Authors
Submitted to: Meeting Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: August 20, 2013
Publication Date: N/A
Technical Abstract: The low-precipitation zone of the Columbia Plateau in the Pacific Northwest encompasses 1.6 million cropland hectares in central Washington State and northern Oregon. This region is an ideal agroecosystem to test on a landscape scale how management practices and climate impact the populations of biocontrol agents. Over a period of four years we carried out an extensive survey of this region and tracked populations and genetic diversity of indigenous biocontrol Pseudomonas spp. We also monitored the levels of antibiotics in the rhizosphere of field-grown cereals. Results of the survey revealed the widespread abundance of indigenous phenazine (Phz+) and 2,4-diacetylphloroglucinol (Phl+) producing rhizobacteria. Phl+ pseudomonads dominated higher precipitation areas and irrigated wheat fields. In contrast, Phz+ rhizobacteria were predominantly associated with non-irrigated dryland cereal crops, produced microgram amounts of phenazines in the rhizosphere of dryland wheat and effectively controlled Rhizoctonia root rot. Both Phz+ and Phl+ Pseudomonas communities exhibited extensive genetic diversity. Despite having both been isolated from roots of wheat grown in the Pacific Northwest, strains 2-79 (Phz+) and Q8r1-96 (Phl+) shared only 63.9% of their predicted proteomes. Our results show that precipitation and cropping practice are major factors in the geographic distribution, abundance and activity of indigenous biocontrol pseudomonads in the rhizosphere of commercially grown cereal crops.