Effects Of Sinorhizobium Fredii WGE03and Its Sulfur Metabolic Mutants Inoculation On Soybean Growth And Rhizosphere Bacterial Communities

It was the first time to study the effects of Sinorhizobium fredii WGF03and its two mutants inoculation on soybean growth and rhizosphere bacterial communities in the field condition. The mutants were105.26and CysH2+17, whose sulfur metabolic relevant gene cysDN or cysH was destroyed respectively.There were four treatments for soybean planting. They were WGF03inoculation,105.26inoculation, CysH2+17inoculation and non-inoculation. The plant height, dry weight, product and nodule number were used to analyze the inoculation impacts on soybean growth. SPSS analysis of the plant height and dry weight showed that the treatment of WGF03inoculation was significantly better than other treatments. Meanwhile, there was no significant difference among the treatments of105.26inoculation, CysH2+17inoculation and non-inoculation. What’s more, compared to the treatment of non-inoculation, average nodule numbers of flower and mature stages showed that the treatment of WGF03inoculation was24.08%and22.99%higher, and average yield increased39.08%. Those measurements of the other three treatments stayed the same. The rhizosphere soil of all treatments were carefully collected on the stage of flower and mature. And then16S rDNA V3region and V6-V8region were amplified after extracting the total microbial DNA of each soil sample, finally the DGGE gel was run. Bio-softs such as Quantity One V4.6.2, Canoco4.5and MEGA5.1were used for comprehensive analysis, and indexes such as simple index(Ii),Shannon-Weiner index(H) and Sorenson’s index of similarity(Cs) were also calculated. Both V3region and V6-V8region DGGE profiles analyses indicated that all inoculation treatments have some kind of effect on the bacterial diversity and community structure of all rhizosphere soil samples. Inoculation possibly affected the biomass of somewhat kinds of bacteria. The dominant factor affected the rhizosphere bacterial community was the growth of soybean. Sequencing results of the excised bands from V3region and V6-V8region DGGE gels illustrated that the dominant bacteria were varied and no obvious specific genus or species was found. Meanwhile Proteobacteria was absolutely dominant phylum and a-Proteobacteria and y-Proteobacteria were the main classes.In conclusion, Wild type rhizobium strain WGF03was able to enter into the root of soybean, thus promoted the growth and product of soybean. Because of the damaged sulfur metabolic relevant genes, the mutants lost promotion function. All three rhizobium strains have certain effect on the rhizosphere bacteria communities, which were likely due to the symbiosis between these rhizobium with soybeans. This view still needs to be confirmed by more studies.