Growth promotion of winter wheat by fluorescent pseudomonads under field conditions

The ability of some pseudomonad strains to promote growth and yield of winter wheat was assessed at field sites during 1988 and 1989. The Kernen and Hagen sites were located on Dark Brown Chernozemic and Orthic Black Chernozemic soils, respectively. Plants were inoculated either by injecting a bacterial suspension into the rhizosphere of 250-day old plants in the spring (1988 study) or by soaking seeds in a bacterial suspension prior to fall planting (1989 study). Resistance to rifampicin and nalidixic acid (Rif r Nal r) was used to differentiate introduced pseudomonads from indigenous soil bacteria. Pseudomonad inoculants injected into a rhizosphere produced winter wheat grain yields 1.05-2.08 times the control, but these increases were not significant due to variability between field plot replicates. The Rif r Nai r inoculant P. cepacia MR85 resulted in the highest number of tillers and increased dry weight of seeds by 1.53- and 2.08-fold at the 1988 Hagen and Kernen sites, respectively. When used as seed inoculants P, cepacia R85 and P. putida R105 stimulated ( P < 0.05) grain yield by 11 % at both the Kernen and Hagen sites. Likewise, two Rif r Nal r inoculants, P. cepacia MR85 and P. putida MR111 significantly ( P < 0.10 and P