Siderophoregenic Bradyrhizobia boost yield of soybean

After screening for siderophore (microbial iron chelator) production, of seven available cultures of soybean (Glycine max L.) root nodule bradyrhizobia, one strain, Bradyrhizobium japonicum NCIM 2746, was selected to confirm its phytopathogenic suppression and soybean growth promotion. Based on chromatographic and spectrophotometric studies, two different siderophores, a hydroxamate type (MW 734) and another catecholate type (MW 1000), were observed. Randomized block design (RBD) analysis of sick-pot studies (soil inoculated with phytopathogens) with an MACS 124 variety of soybean, bacterized with siderophoregenic B. japonicum, showed a marked increase in the percentage of germination, nodulation, chlorophyll, oil, protein content, and number of pods. Field trial study confirmed these pot results, which were evident from enhancement in shoot length, number of branches, chlorophyll content, number of nodules, root length, and number of pods. These results suggest the possibility of exploiting B. japonicum NCIM 2746 as a potential bioinoculant.