Phosphate-solubilizing bacteria from safflower rhizosphere and their effect on seedling growth

Phosphate-solubilizing bacteria (PSB) can convert insoluble rhizosphere phosphorus into forms that are absorbable by plants and thus enhance the growth of plants. Safflower is a cash crop that is a source of vegetable oils, food coloring and flavoring agents. This study sought to isolate PSB in safflower rhizosphere soil and investigate their effects on seedling growth. The isolated PSB were identified as belonging to the genera Pseudomonas, Sinorhizobium, Staphylococcus, Acinetobacter and Enterobacter using 16S rRNA gene sequence analysis. Acinetobacter sp RC04. showed the best performance in phosphate solubilization, with the efficiency of the process being influenced by carbon source, nitrogen source, cultivation temperature and initial culture pH. Acinetobacter sp. RC04 and Sinorhizobium sp. RC02 showed the ability to improve safflower seed germination and, when co-inoculated, improved seedling growth. Hence, we suggest that Acinetobacter sp. RC04 and Sinorhizobium sp. RC02 could be developed for field application to promote safflower growth. The results from this study will help drive novel biofertilizer discovery and could be included in integrated nutrient management regimes for safflower and other important economic crops