DIFFERENTIAL RESPONSE OF WESTERN HEMLOCK FROM LOW AND HIGH ELEVATIONSTO INOCULATION WITH PLANT GROWTH-PROMOTING BACILLUS-POLYMYXA

The influence of inoculation with plant growth-promoting Bacillus poly myxa strains L5 and L6-16R was evaluated on the performance of western hemlock [Tsuga heterophylla (Raf.) Sarg.] using seed that originated from six British Columbia provenances that differed primarily in eleva tion(from 152 to 1190 m above sea level). Preliminary analysis reveale d a tendency for hemlock originating from high and low elevations to r espond differently to bacterial inoculation, therefore subsequent anal yses were performed after pooling data into two elevational groups: th e three hemlock provenances located at the lowest elevations; and the three found at the highest elevations. B. polymyxa strain L6-16R-inocu lated seed from the low elevation group produced an average of 2.38-fo ld (P < 0.025) more seedlings than uninoculated controls midway throug h the emergence period, and 1.41-fold (P < 0.05) more seedlings than u ninoculated controls when emergence was complete. Inoculation of low e levation hemlock seed with strain LS or of high elevation seed with ei ther bacterial strain did not significantly affect seedling emergence. In contrast to the effects observed on emergence, growth of hemlock s eedlings in the low elevation group was unaffected by inoculation with either bacterial strain, but strain L6-16R-inoculated high elevation seed produced seedlings that were significantly taller (1.19-fold; P < 0.05) and heavier (1.30-fold; P < 0.05) than uninoculated controls. S train L5 did not stimulate growth of high elevation seedlings signific antly. Hemlock rhizosphere colonization by strain L6-16R was assessed on seedlings that originated from one of the low elevation provenances and was found to be 1.7 x 10(3) cfu g(-1) dry root tissue. These resu lts indicate that seed inoculation with B, polymyxa strain L6-16R can result in colonization of western hemlock root systems and in signific ant increases in seedling emergence, height and biomass accumulation; however, the type of seedling growth response to inoculation with B. p olymyxa may depend on the elevation of the provenance from which seed originates.