GROWTH PROMOTION OF GENETICALLY IMPROVED Pinus taedaSEEDLINGS BY INOCULATION WITH SPECIES OF Bacillus

Abstract

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.