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

The influence of plant growth promoting rhizobacteria on field performance of hybrid spruce (Picea glauca x engelmannu) was investigated by inoculating seedlings with rhizobacteria capable of stimulating seedling growth in a controlled environment. Two spruce ecotypes (from Mackenzie and Salmon Arm, British Columbia) and two bacterial strains previously isolated from naturally regenerating seedlings of each spruce ecotype were evaluated. Planting trials were conducted in the ecosystem from which each spruce ecotype and associated bacterial strain were originally collected, and at two alternative sites. Hydrogenophaga pseudoflava, which was isolated from Mackenzie spruce seedlings, caused increases 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 inhibitory effects in three others. There was no indication that growth promotion was related to a common ecotypic origin of seedlings and rhizobacteria, or that bacteria were more effective in the ecosystem from which they were originally isolated. However, Salmon Arm spruce growth promotion by H. pseudoflava was greatest at the poorest quality planting site.