ISOLATION AND MOLECULAR CHARACTERIZATION OF RHIZOBIAL STRAINS ISOLATED FROM SOYBEAN NODULES IN LIMPOPO PROVINCE, SOUTH AFRICA

Limited nitrogen in the soil is a major constraint to sustainable crop production in most developing countries including South Africa. Soybean productivity in South Africa is limited by drought, poor soil fertility, and the ineffectiveness or unavailability of native strains. Most soil in South Africa contains low or ineffective rhizobium strains for biological nitrogen fixation in legume crops. The study aimed to isolate and characterize compatible rhizobial strains for soybeans in response to soil moisture conservation technologies and Bradyrhizobium japonicum inoculation in Limpopo province, South Africa. The study used a phylogenetic analysis of 21 bacteria' 16S rRNA gene sequences isolated from soybean root nodules in the Limpopo province. Experiments were conducted at Syferkuil farm and Lebopo sites in Limpopo province. DNA was extracted to perform PCR amplification of the 16S ribosomal RNA using primer fD1 and rD1. Sequencing was done at Inqaba Biotec, Pretoria, and edited using Bioedit and Mega X programs. A total of 21 bacterial isolates were isolated from soybean root nodules. The isolated strains from Syferkuil and Lebopo sites had both medium-growing and fast-growing strains; however, they were dominated by fast-growing strains. Phylogenetic results showed four categories of bacterial genera: Agrobacterium, Bradyrhizobium, Bacillus, and Rhizobium. Application of local rhizobium strains and efficient strains could enhance productivity and contribute to the low input cost of soybean production in Limpopo province