Molecular Characterization of Root-Nodule Bacteria from Soybean (Glycine Max L. Merrill) Rhizosphere in Three Agro-Ecological Systems in Nigeria

The worldwide increase in population continues to threaten the sustainability of agricultural systems since agricultural output must be optimized to meet the global rise in food demand. This study examined the symbiotic compatibility between indigenous rhizobia population and soybean plant. Soil samples 5kg each were randomly collected from agricultural fields in a total of nine different local governments from Southwest and North central zones of Nigeria at a depth of 0-30cm using sterile soil auger (5cm diameter). The control soil samples were obtained from Badagry beach (a location with no previous history of soybean cultivation). The indigenous microbial population were isolated using serial dilution technique and they were cultured using nutrient agar (NA), yeast-extract mannitol salt agar (YEMA) and sabouraud dextrose agar (SDA) incubated at 26±2oC for 48 hours and 3-5 days respectively. Soybean seeds were sown in each of twenty pots aseptically. The mean pH of soil samples from this study was 6.0 (slightly acidic) while NO3 ˉ N and NH4 ˉ N was relatively low. Molecular characterization of these rhizobia species as well as their genetic diversity in soil were investigated. A total of nine different rhizobia species were isolated from all the soil samples and three of the nine isolates were randomly selected for molecular characterization using 16S rRNA gene sequencing method. The accession number for the selected organisms were confirmed as follows; 0J7 (Accession number: MN0677451.1), Stenotrophomonas maltophilia OJ8 (Accession number: MF767518.1) Agrobacterium tumefaciens, OJ9 (Accession number: NR_181268.1) Rhizobium rhizolycopersici. The other isolates were characterized as Bradyrhizobium japonicum