Growth promotion ability of phosphate-solubilizing bacteria from the soybean rhizosphere under maize-soybean intercropping systems

BACKGROUND Optimum cultivation and management measures are needed to increase the phosphorus (P) absorption efficiency of crops for sustainable agricultural production. Previous studies indicated that leguminous crops can promote P absorption by neighboring gramineous crops. In this study, we isolated and screened the phosphate-solubilizing bacteria (PSB) from soybean rhizosphere under a maize-soybean intercropping system in Southwest China, and nine PSBs with high P-solubilizing ability were identified. RESULTS 16S rDNA sequencing and phylogenetic analysis showed that these PSBs belong mainly to Bacillus and Pseudomonas. The phosphate solubility of Bacillus aryabhattai B8W22 reached 388.62 mu g mL(-1). High-performance liquid chromatographic analysis showed that each strain could secrete a large quantity of organic acids, including oxalic acid, malonic acid, citric acid and succinic acid. In addition, all strains produced indole acetic acid (IAA) and siderophores that could promote plant growth. Seed germination experiments testified that PSBs isolated in this study have an innate ability to promote plant growth. The plant culture pot experiment further illustrated that soil acid phosphatase (ACP) activity and available P content, as well as plant P uptake, increased significantly with PSBs inoculation. CONCLUSION PSBs from the rhizosphere soil of intercropped soybean could secrete organic acids that increase the solubilization of unavailable P, improve soil ACP activity and P availability, and produce IAA and siderophores that promote maize seed germination and seedling growth. Our findings indicate the PSBs from soybean rhizosphere have significant potential to reduce the application of chemical phosphate fertilizers and to promote sustainable agricultural development. (c) 2021 Society of Chemical Industry.

Automated summary

The phosphate-solubilizing bacteria (PSB) isolated from the rhizosphere of intercropped soybean have the potential to promote plant growth by secreting organic acids and enhancing plant P uptake. Inoculation of PSBs significantly increases soil acid phosphatase activity and available P content.