Genetic diversity and plant growth-promoting activity of the dominant bacteria from canola plants in Western Iran

Background Plant growth-promoting bacteria (PGPB) can be used as a safe and sustainable agricultural measure to increase plant yield. In this study, cultivable rhizospheric, endophytic, and epiphytic bacteria associated with canola were isolated on nutrient agar medium. The SDS-PAGE method was used for grouping the bacterial strains. Bacterial strains with more than 80% similarity in their protein patterns were placed in the same species and selected as a representative for partial 16S rRNA encoding gene sequence analysis. Results It was found that the bacteria used in this study belonged to Pseudomonas, Frigoribacterium, Sphingomonas, Sphingobacterium, Microbacterium, Bacillus, and Rhodococcus genera. Three PGP bioactivities including siderophore production, nitrogen fixation ability, and phosphate solubilization were evaluated for 18 Pseudomonas representative strains. All tested strains were able to produce siderophore, although only 5 strains could fix nitrogen and none was able to solubilize phosphate. Greenhouse experiments showed that 4 bacterial strains (i.e., 8312, 642, 1313W, and 9421) significantly affected canola seed germination and seedling growth. Bacterial strain 8312, which was identified as Pseudomonas sp., showed the highest effect on the growth of the canola plant. These results indicated the potential of strain 8312 to be used as a biofertilizer in canola cultivation. Conclusions The results of this research indicated that canola-related bacteria were diverse during the flowering stage. One isolate had a significant effect on all canola plant growth factors in the greenhouse. Hence, it is recommended to investigate this strain further in field infestation experiments.