Isolation, identification, and growth-promoting ability of efficient silicate-solubilizing strains

Abstract:

[Background] Silicon, which improves the stress resistance, yield, and quality of crops, has been widely reported. However, the conventional neglect of silicon fertilizer results in the continuous decrease in the content of available silicon in arable land. Therefore, it is an urgent task to raise the content of soil available silicon. [Objective] The content of available silicon in soil affects the absorption and utilization of silicon by crops. Silicate-solubilizing microorganisms can continuously activate available silicon in soil, which helps improve crop yield and quality and reduce the application rate of chemical fertilizer. [Methods] Selective media were used for the enrichment, isolation, and purification of soil silicate-solubilizing strains, and the silicate-solubilizing ability, saline-alkaline tolerance, low-oxygen tolerance, phosphate-solubilizing ability, potassium-releasing ability, and cellulose-degrading ability were determined. With malachite green as the primary stain and safranin as counterstain, the spore yield of high-efficiency silicate-solubilizing strains was measured. Finally, the maize growth-promoting ability of efficient silicate-solubilizing strains was investigated through pot experiment. [Results] Two efficient silicate-solubilizing strains were obtained, MB22 and MB35-5. They were identified as Priestia aryabhattai by 16S rRNA sequencing, and the concentration of available silicon in the culture of them was 1.5 and 1.7 folds that of the blank control, and 1.1 and 1.2 folds that of the control Paenibacillus mucilaginosus 3016, respectively. MB22 and MB35-5 showed high saline-alkaline tolerance, particularly MB35-5. Specifically, under the conditions of pH 10, 10% NaCl, and 10% KNO₃, the concentration of available silicon in the culture of MB35-5 was 0.28–0.37 mmol/L. The spore yield of MB22 and MB35-5 was 68% and 55%, respectively, 1.69 folds and 1.37 folds of the control strain, respectively. MB35-5 had phosphate-solubilizing ability, potassium-releasing ability, and cellulose-degrading ability. Pot experiment showed that the two strains significantly increased the plant height and root dry weight of maize plants, especially MB35-5. To be specific, the average height of plants treated by MB35-5 was 1.39 times that of blank treatment and 1.14 times that of plants treated by control strain. The root dry weight of plants treated by MB35-5 was 1.37 times that of the blank treatment and 1.24 times that of plants treated by control strain 3016. [Conclusion] The silicate-solubilizing strains MB22 and MB35-5 were screened out. Among them, MB35-5 with high spore yield also showed phosphate-solubilizing ability, potassium-releasing ability, cellulose-degrading ability, and growth-promoting function, as well as the saline-alkaline tolerance and low-oxygen tolerance. Thus, this strain should be further tested and developed.

Key words:silicate-solubilizing strain;Bacillus;saline-alkaline-tolerant bacteria;spore yield;promoting plant growth