An assessment of spruce growth response specificity after inoculation with coexistent rhizosphere bacteria

The influence of inoculation with rhizosphere bacteria on hybrid spruce (Picea glauca × engelmannii) seedling growth was investigated by isolating bacteria from the rhizosphere of naturally regenerating spruce seedlings collected from two ecologically distinct zones of British Columbia. Forty bacterial strains from spruce were screened in a seedling growth experiment, and several strains were shown to stimulate spruce seedling growth. The three most effective spruce growth promoting strains from each ecological zone were then tested in a seedling growth response specificity experiment in which seed, soil, and bacteria from both spruce ecosystems were examined in all possible treatment combinations, including pasteurized soil. Spruce seedling growth was primarily affected by seed and soil source (Salmon Arm > Mackenzie for both factors), and by soil pasteurization (pasteurized > unpasteurized). Significant growth effects due to bacterial treatment in the specificity experiment occurred only in pasteurized ...