Inoculation of Pinus taeda Seedlings with Plant Growth-promoting Rhizobacteria

ABSTRACT The aim of this study was to evaluate the effect of Azospirillum brasilense , Bacillus subtilis and Pseudomonas fluorescens on the growth of Pinus taeda seedlings. Bacterial inoculants were applied in two different forms: at sowing and 20 days after emergence. At 30, 60 and 90 days after emergence, we evaluated plant height and root-colar diameter. At 180 days after emergence, we also measured shoot and root dry weight. Data were analyzed by analysis of variance and means were ranked by Duncan’s test. The most pronounced results were observed for root and shoot biomass when plants were inoculated with Bacillus subtilis and Pseudomonas fluorescens. Bacillus subtilis increased root and shoot biomass by 67.1% and 33.1%, respectively, when comparing values with those of non-inoculated plants. On the other hand, inoculation with Pseudomonas fluorescens decreased root biomass up to 31.42%. Inoculation with Azospirillum brasilense did not promote any difference in Pinus taeda seedling growth and may not be an efficient alternative for inoculation practices. According to these results, inoculation of Pinus taeda seedlings with Bacillus subtilis has great potential to improve plant growth regarding adaptation to field conditions.