Submitted to: International Plant Growth Promoting Rhizobacteria Workshop
Publication Type: Abstract Only
Publication Acceptance Date: June 1, 2006
Publication Date: May 30, 2006
Citation: Slininger, P.J., Shea Andersh, M.A. 2006. Proline-based modulation of 2,4-diacetylphloroglucinol and viable cell yields in cultures of Pseudomonas fluorescens wild and over-producing strains [abstract]. International Plant Growth Promoting Rhizobacteria Workshop. Paper No. P57. Technical Abstract: The antifungal compound 2,4-diacetylphloroglucinol (DAPG) is produced in the rhizosphere of wheat by Pseudomonad populations responsible for the natural biological control phenomenon known as "take-all decline." Studies were conducted to elucidate the impact of DAPG and its co-product 2,4,6-trihydroxyacetophenone (THA) on the production of Pseudomonas fluorescens for biological control. Increasing DAPG from 0.1 to 0.5 g/L and THA from 0.05 to 0.5 g/L significantly inhibited the growth and lowered the yield of viable bacteria in liquid cultures. On further examination of these metabolites applied in seed coatings, levels of DAPG and THA exceeding 0.05 mg/g seed significantly reduced wheat germination percentages. The three-way interaction of DAPG, THA, and culture medium ingredients was significant, and greatest seed germination loss (40-50%) was observed when 0.5 mg DAPG and 0.25 mg THA were combined in a coating of 0.5 mL culture medium/g seed. Based on results of Biolog Microplate GN, flask and fermentor screens of carbon sources, proline was found to optimize the viable cell yields of the P. fluorescens strains tested. The combination of proline with glucose and urea as C and N sources in growth media could be optimized to minimize DAPG production and maximize the vitality of P. fluorescens cultures, Q8R1-96 and the DAPG-over-producer Q69c-80:miniTn5:phl20. In production cultures, proline supply rate offers a potentially useful means to optimize biological control agent yield and quality.