Molecular differentiation of plant beneficial Bacillus strains useful as soil agro-inoculants

Plant rhizosphere is rich in bacterial cells of Bacillus species. This bacterial genus includes a large number of strains with beneficial properties for plant protection and growth promotion. For this study we selected seventeen beneficial strains of Bacillus spp., isolated from food products, legume rhizosphere and agricultural soils from south and south-east areas of Romania. The selection was based on their ability to inhibit the growth of several plant pathogens and to produce different enzymes and metabolic compounds with beneficial traits for plant protection and growth promotion, as it was presented in our previous studies. For a successful use of such beneficial bacteria as agro-inoculants, their survival in natural ecosystems should be in sufficiently high levels to produce the intended purpose. The best way considered for the evaluation of their fate is the analysis in situ of the inoculated bacterial strains. For differentiating the inoculated Bacillus beneficial strain from other indigenous bacilli present in the environment, the molecular techniques seem to be the proper way, if we refer to the accuracy, time consumption and financial resources. In our study, RAPD analysis was used for the molecular analysis of selected strains. According to our results, the use of RAPD-PCR technique with OPE-02, OPE-20 and OPM-15 primers can offer a good differentiation of Bacillus strains recommended as agro-inoculants. Using strain specific markers, inoculated bacteria could be accurately detected after their application in soil.