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This study was carried on evaluating effects of inoculation with Bacillus speciesand generations of genetically improved seeds on Pinus taeda growth in nursery conditions. Two experiments, based on distinct inoculation methods (sowing and post-emergence) were performed under a 3 x 2 factorial, completely randomized block design (3 levels of inoculation and 2 levels of genetic improvement of Pinus taeda). Plant height and diameter were measured at different stages along seedling development. At harvest, root volume, root fresh and dry mass, shoot fresh and dry mass and quality index were also estimated. Data were submitted to a two-way analysis of variance (p<0.05) and Tukey ́s test was used to separate means (p<0.05). Data from experiment with inoculation at sowing showed that Bacillus amyloliquefaciens improved plant height (20%) and shoot dry mass (28%) of 2.0 generation seedlings compared to control plants. Regarding post-emergence inoculation, plants from 1.5 generation presented more pronounced effects of Bacillus amyloliquefaciens. Overall, inoculated seedlings were 9.8% taller and produced 60% more root dry mass than non-inoculated plants. Regardless of seedling generation, B. amyloliquefaciens increased Dickson Quality Index by 30%. These results suggest that each generation of genetically improved P. taeda has different growth responses to B. amyloliquefaciens. Methods of inoculation, combined with level of genetic improvement, must also be considered to obtain the best benefit to seedling development when using this rhizobacterium. Based on the current findings, inoculation with B. amyloliquefaciens should be incorporated as a silvicultural practice to improve growth of P. taeda under nursery conditions.