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.摘要 本研究旨在评估巴西固氮螺菌（Azospirillum brasilense）、枯草芽孢杆菌（Bacillus subtilis）与荧光假单胞菌（Pseudomonas fluorescens）对火炬松（Pinus taeda）幼苗生长的影响。菌剂采用两种施用方式：播种时及出苗后20天。分别于出苗后30、60、90天测定植株株高与根颈直径；出苗后180天测定地上部与地下部干重。数据采用方差分析，均值通过邓肯氏检验进行多重比较排序。接种枯草芽孢杆菌与荧光假单胞菌的植株，其根系与地上部生物量变化最为显著。与未接种对照组相比，枯草芽孢杆菌可使根系与地上部生物量分别提升67.1%与33.1%。而荧光假单胞菌接种则使根系生物量降低至多31.42%。巴西固氮螺菌接种未对火炬松幼苗生长产生显著影响，不适宜作为接种实践的高效备选方案。综上，采用枯草芽孢杆菌接种火炬松幼苗，在提升植株生长以适应田间环境方面具有巨大应用潜力。