Isolation and Characterization of Rhizobacteria for their Many Activities Improving the Plant Growth

Abstract

The use of microbial technology in agriculture extends currently relatively quickly with the identification of new more efficient bacterial strains in the growth of plants. The rhizobacteria that promote the growth of plants (PGPR, plant growth promoting rhizobacteria) can have a positive effect on the productivity of crops( Chaiharn et al., 2008) especially when subjected to salt stress ( Tripathi et al., 1998). Indeed, the salinity considerably affects the crop yield. Inoculating PGPR can mitigate the effects of this type of stress by direct or indirect mechanisms (Ahmad et al., 2008). To select effective strains and having multiple activities, a total of 22 bacterial strains are isolated from different soils. These strains are characterized by their ability to fix nitrogen (nitrogen-free medium culture). They are also tested in vitro for their activities of improvement of plant growth such as the production of the indole acetic acid (IAA) of hydrogen cyanide (HCN), of the siderophore, ammonia (NH3), of solubilization of phosphates and antifungal activity. More than 70% of the strains produce NH3, 54% solubilized more P2O5 10µg/ml and the same rate and has antifungal activity against ≥ to three fungal strains. However, 36% produce more 80µg/ml of IAA, 27% produce siderophores and only two strains produced of HCN. The production of IAA of eight (08) strains is evaluated in the presence of 100, 200 and 300 mM NaCl. The remaining active strains with high concentration of NaCl would be the most effective and can be considered as biofertilizers for improving plant growth in areas affected by salinity.