Isolation, Characterization and Identification of Plant Growth Promoting Rhizobacteria from Cauliflower (Brassica oleracea)

Bio-fertilizers are currently being considered as effective and environmentally-safe alternatives to synthetic fertilizers. In recent years, the use of many Rhizobia in the growth of many plants has found commercial utilization in developing countries especially as growth promoters. This study was conducted to isolate Rhizobacteria from the rhizosphere, rhizoplane and endorhizosphere of cauliflower (Brasicca oleracea) collected from ChattaBakhtawar, Islamabad, Pakistan. Luria-Bertini (LB) media was used to isolate rhizobacterial strains. The identification of rhizobacteria was done by studying many morphological characteristics of colonies growing on the media. These characteristics include Form, Elevation, Margin, Opacity and Colour; these were recorded periodically. For the confirmation of rhizobacteria; biochemical tests were performed. Gram staining was done for 14 strains CF-ES-4, CF-ES-5A, CF-ES-5B, CF-ES-5C, CF-ES-6A, CF-ES-6B, CF-RP-4C, CF-RP-4B, CF-RP-6, CF-RP-5A, CF-RP-4, CF-RS -4, CF-RS-5, and CF-RS-6: Among these, 11 strains were Gram negative while the 3 strains CF-RP-5A, CF-ES-5A and CF-RP-4 were Gram positive. The strains which were phosphate negative  CF-RP-4C, CF-RS-8, CF-RP-4A, CF-ES-4, CF-RS-7, CF-ES-5C, CF-RP-6 while the CF-RP-5A CF-RP-5B, CF-ES-5B, CF-ES-5A, CF-RP-4B, CF-ES-6B, CF-RS-4 and CF-RS-6 strains were phosphate positive; these confirmed qualities of rhizobacteria. Extraction of rhizobacteria was also done and the composition was maintained accordingly as for biofertilizers. Taken together, the present investigation adds more information to current understanding of the mechanism of Nitrogen-fixing by rhizobacteria and will be useful for the commercialization of these strains to improve the yield of economic plants. Thus, isolation of Rhizobia and its use in agricultural field practice should be adopted.