Isolation and characterization of a novel silicate-solubilizing bacterial strain Burkholderia eburnea CS4-2 that promotes growth of japonica rice (Oryza sativa L. cv. Dongjin)

The current study aimed to isolate and identify japonica rice (Oryza sativa L. cv. Dongjin) root-associated rhizobacteria and to investigate their ability to solubilize silicate, produce indole acetic acid (IAA), promote plant growth, and encourage silicon (Si) uptake and deposit in plants. A single bacterial isolate was selected on the basis of its silica-solubilizing ability and IAA production. The 16S rRNA gene sequence of the isolate identified it as Burkholderiaeburnea CS4-2. Burkholderiaeburnea CS4-2 produced high amounts of IAA at pH 8. When combined with silica fertilization, soil inoculation with CS4-2 promoted all growth attributes over those of the water-treated (control) and insoluble silica-fertilized plants. Microscopic observations also demonstrated a significant difference in the Si deposits on the leaf epidermis of rice plants under different treatments, indicating that more Si was deposited in plants fertilized with both B. eburnea CS4-2 and insoluble silica than in either insoluble silica-fertilized or water-treated plants. Inductively coupled plasma spectrometry analysis confirmed the same trend of Si concentration in whole-plant biomass of the rice that received the same treatments, respectively. Therefore, we conclude that B. eburnea CS4-2 has the ability to produce IAA under high-pH conditions, solubilize silicate, and promote plant growth.