In vitro Enhancement of Soybean PAn1532 under Drought Stress Condition Using Rhizobium spp. Isolated from the Root Region of Bambara Plant

Food security is seriously under threat in many developing countries as agriculture is becoming unsustainable due to drought stress caused by climate change, besides, the world population increase and hunger is already a problem. There is therefore an urgent need for a sustainable means to accomplish food availability in these regions. Bambara rhizospheric soil was collected by destructive sampling and standard culture dependent techniques were used to isolate and characterize the bacteria. Plant growth promoting traits and in vitro drought tolerant tests were carried out for all the bacterial isolates. Amplified PCR products were sequenced, cleaned, blasted in NCBI, sent to Gen-bank for accession number and phylogenetic tree was drawn. The isolates were identified to be Rhizobium spp. and Sinorhizobium meliloti. All the bacterial spp. produced siderophore, ammonia and indole-acetic acid. Rhizobium tropici, R. cellulosilyticum and S. meliloti produced hydrogen cyanide while Rhizobium sp. and R. taibaishanense were negative to hydrogen cyanide test. All the bacterial isolates were tolerant to in vitro drought experiment but Rhizobium sp. and R. cellulosilyticum showed the highest significance tolerance with optical density (OD) values of 1.35 and 0.32 respectively at a concentration of 30% polyethylene glycol (PEG) while S. meliloti had the least OD value of 0.17 at the same concentration. The results of the ability of Rhizobium sp., R. cellulosilyticum and S. meliloti to enhance the growth of soybean PAn1532 in vitro under drought stress condition showed that soybean inoculated with R. cellulosilyticum had significant higher root dry weight (P<0.05) than the those amended with Rhizobium sp. and S. meliloti. These findings showed that Rhizobium sp. can be further harnessed to enhance the growth of agronomic crops like soybean under drought conditions especially in semi-arid and arid regions of the world.