FIRST YEAR FIELD PERFORMANCE OF SPRUCE SEEDLINGS INOCULATED WITH PLANT-GROWTH PROMOTING RHIZOBACTERIA

The influence of plant growth promoting rhizobacteria on field perform ance of hybrid spruce (Picea glauca x engelmannu) was investigated by inoculating seedlings with rhizobacteria capable of stimulating seedli ng growth in a controlled environment. Two spruce ecotypes (from Macke nzie and Salmon Arm, British Columbia) and two bacterial strains previ ously isolated from naturally regenerating seedlings of each spruce ec otype were evaluated. Planting trials were conducted in the ecosystem from which each spruce ecotype and associated bacterial strain were or iginally collected, and at two alternative sites. Hydrogenophaga pseud oflava, which was isolated from Mackenzie spruce seedlings, caused inc reases in seedling biomass or branch number of up to 49%, but was most effective as a root growth promoter of the Salmon Arm spruce ecotype. Pseudomonas putida, which originated from Salmon Arm spruce seedlings , increased seedling biomass or branch number in two trials, but had i nhibitory effects in three others. There was no indication that growth promotion was related to a common ecotypic origin of seedlings and rh izobacteria, or that bacteria were more effective in the ecosystem fro m which they were originally isolated. However, Salmon Arm spruce grow th promotion by H. pseudoflava was greatest at the poorest quality pla nting site.