INOCULATION OF CONIFER SEED WITH PLANT-GROWTH PROMOTING BACILLUS STRAINS CAUSES INCREASED SEEDLING EMERGENCE AND BIOMASS

Seed inoculation with Bacillus strains L5 and L6 significantly increased the rate of seedling emergence of white spruce but did not affect subsequent seedling growth. Lodgepole pine root growth was promoted by strain L5 in sterilized, but not non-sterile growth medium. Strain L6 promoted pine root growth in sterilized medium, but also caused significant increases in seedling emergence, shoot weight and height, root weight and surface area, and root collar diameter when tested in non-sterile peat-vermiculite medium. The positive effects due to a single inoculation of pine with strain L6 at sowing were not detectable after 12 weeks growth. However, root growth was stimulated after 16 weeks growth if seedlings were re-inoculated with strain L6 mid-way through the experiment. Shoot-growth promotion was also detected when 1 yr old lodgepole pine seedlings were planted in pots and inoculated with strain L6. Douglas-fir seedlings grown from seed inoculated with strain L5 had increased root collar diameters, whereas those inoculated with strain L6 exhibited increased root surface area.