Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: June 20, 2005
Publication Date: June 20, 2005
Citation: Allende-Molar, R., Paulitz, T.C., Weller, D.M. 2005. Populations of 2,4-diacetylphloroglucinol (dapg)-producing pseudomonas fluorescens in the rhizosphere of pythium-infected wheat. Phytopathology. 89: S4 Technical Abstract: Root infections by soilborne pathogens can either positively or negatively affect root colonization and antibiotic production by beneficial bacteria. We tested the impact of four Pythium spp. on colonization of wheat roots by indigenous populations of 2,4-diacetylphloroglucinol (DAPG)-producing Pseudomonas fluorescens in Washington State suppressive soils. Soils were cycled to wheat (cv. Penawawa) to reactivate and increase indigenous populations of the DAPG producers to a density greater than 105 CFU/g fresh root. Soils were then infested with P. abappressorium, P. irregulare, P. debaryanum or P. ultimum at a rate of 10 3 CFU/g soil. In addition, 0.5% ground rolled oats was added to infested soils. Seven days after amending the soil, pregerminated wheat seed was sown. Rhizosphere populations of DAPG-producing bacteria were assessed using the PCR-based dilution end point assay 2 weeks after sowing. Populations of DAPG-producing P. fluorescens were similar in both infested and non-infested soils. None of the Pythium spp. affected the populations of indigenous DAPG-producing P. fluorescens on the wheat roots.