Influence of co-inoculation of Bradyrhizobium japonicum and Pseudomonas fluorescens on growth of soybean (Glycine max L.)

Soybean (Glycine max L.) is a very important legume in the human diet as well as fodder crop. Previous studies have reported that co-inoculation with PGPR (plant growth-promoting bacteria) and rhizobia promotes symbiotic nitrogen fixation efficiency, increases plant nitrogen content and reduces the occurrence of soybean diseases, thus reducing pesticide use, and protecting the environment. The aim of this study was to determine the impact of co-inoculation of soybean seeds with different strains of nodule bacteria Bradyrhizobium japonicum as well as PGPR (Pseudomonas fluorescens). Indigenous strains of beneficial bacteria used in this research were isolated from different locations in Croatia. Isolates were identified by performing 16S rRNA gene sequencing. The application of different strains of nodule bacteria resulted in a statistically justified effect on all investigated properties, with the exception of root length. A positive influence of P. fluorescens on the increase in shoot dry weight was observed with the co-inoculation with the reference strain B. japonicum and two indigenous strains. The application of P. fluorescens did not show statistically justified differences in any of the investigated properties. Co-inoculation of nodules and PGPR bacteria is a very important biotechnological tool in agriculture, which is why research in this area should definitely be continued and expanded to a larger number of P. fluorescens strains.