Among the 30 bacterial isolates were obtained from Coleus forskohlii rhizospheric soil of Perambalur and Salem districts in Tamil Nadu. All the isolates were identified as Azospirillum spp., Bacillus spp., Pseudomonas spp., and Azotobacter spp. These bacterial strains were tested on morphological, biochemical and screened for their direct growth promoting activities (IAA production, production of Ammonia and Phosphate solubilization) and indirect growth promoting activities (HCN production, Siderophore production). The results obtained showed that among the 30 isolates of Perambalur and Salem districts (P1-P15) and (S1-S15) of ranged from (4.00-9.22x106 and 4.66- 10.00x106) of Azospirillum spp., (3.00-7.66x106 and 3.88-8.00x106) of Bacillus spp., (4.66-12.00 and 4.88-13.00) of Pseudomonas spp., and (2.22-8.00 and 3.66- 9.00) of Azotobacter spp. The IAA production of Pseudomonas spp. (83%), Azospirillum spp (75%), Azotobacter spp. (60%) and Bacillus spp. (30%). Ammonium production of the isolates, Bacillus spp. (96%), Pseudomonas spp. (92%), Azospirillum spp. (65%) and Azotobacter spp. (50%). The highest IAA production of Pseudomonas fluorescens (PPf-1) 7.40 µg/ml and Pseudomonas fluorescens(SPf-1) 7.60 µg/ml followed by other isolates produced from Perambalur and Salem district. Phosphate solubilization of the isolates, Bacillus spp.(83%), Azotobacter spp. (68.47), Pseudomonas spp. (60.56%) and Azospirillum spp. (55%). The siderophore and HCN production produced by all the isolates make it suitable for further investigation of pot and field trials by Coleus forskohlii cultivation.
