ARS | Publication request: REDUCTION OF PHENAZINE-1-CARBOXYLIC ACID ACCUMULATION IN GROWTH CULTURES OFTHE BIOCONTROL AGENT PSEUDOMONAS FLUORESCENS 2-79 ELIMINATES PHYTOTOXIC EFFECTS OF WHEAT SEED INOCULA WITHOUT SACRIFICE TO TAKE-ALL SUPPRESSIVENESS

Submitted to: International Plant Growth Promoting Rhizobacteria Workshop
Publication Type: Proceedings
Publication Acceptance Date: October 10, 1997
Publication Date: N/A

Technical Abstract: The impact of growth culture phenazine productivity on the biocontrol qualities of Pseudomonas fluorescens 2-79 were studied. Fermentor environments varying in temperature (25, 31, 34 deg C), pH (7 or 8), and sources of carbon (glucose, xylose, glycerol, fructose) were selected in order to induce a 0 to 1 g/L range of phenazine-1-carboxylic acid (PCA) accumulations in cultures of Pseudomonas fluorescens 2-79. Cells formulated in 0.5% methylcellulose suspended in either water (MW) or PCA-bearing spent culture broth (MSB) were applied as wheat-seed coatings, and the coated seeds were air dried and stored at 4 deg C for six months. The results of periodic seed bioassays indicated that increasing growth culture phenazine productivity was significantly correlated with increasing germination losses in stored seed treatments, especially in MSB formulations, but also in MW to a lesser extent. The dry storage survival of the biocontrol agent did not vary significantly with the liquid culture conditions used to manipulate phenazine productivity. At least equivalent disease suppression was achieved by cells grown with either low (near zero) or high PCA productivities. These results demonstrate that it is possible to design cell production processes to eliminate accumulation of phytotoxic metabolites without destroying bioefficacy, and that the liquid culture process design can be critical to the success of applying biocontrol agents in seed coatings, a targeted, economical method of field delivery.