Properties of Potential Plant-Growth-Promoting Bacteria and Their Effect on Wheat Growth Promotion (Triticum aestivum) and Soil Characteristics

Abstract

Plant-growth-promoting bacteria are an important economic and environmental resource as biofertilizers that can stimulate plant growth and improve agricultural yields. In this study, potential plant growth-promoting bacteria were isolated from soil samples collected in Russia. Strains that manifested active growth on a nitrogen-free medium, the Pikovskaya medium (with insoluble phosphates) and CAS (Chrome Azurol S) agar, were selected for the study. All bacterial isolates were identified by 16S rRNA gene sequencing analysis. Seventeen bacterial isolates of different species were purified and quantified for their ability to grow on nitrogen-free media; dissolve phosphate; and produce ammonium, indole-3-acetic acid, siderophores, and antifungicidal agents. Principal component analysis identified three groups of strains: one with the maximum signs of providing “plant nutrition”; one with signs of “antimicrobial activity”; and a group “without outstanding signs”. All 17 strains were involved in experiments involving growing inoculated wheat seeds (Triticum aestivum) in pots under natural environmental conditions, and were assessed by their effect on the wheat growth and yield as well as on the chemical composition of the soil. For the “plant nutrition” group, regression analysis revealed a connection between indicators of plant growth, ear length, and ammonium accumulation in the soil. However, in other groups, there were also strains showing a positive effect on plant growth, which suggests the necessity of involving additional factors to predict the ability of strains to affect plants when screened in the laboratory.

The Effectiveness of Co-Inoculation by Consortia of Microorganisms Depends on the Type of Plant and the Soil Microbiome

“…Consortium C was based on the Rothia endophytica GMG9 strain, which demonstrated a high phosphate-immobilizing ability (248.3 µg/mL) in a laboratory experiment [ 13 ]. An active nitrogen fixator, the strain Azotobacter chroococcum GMG39 [ 13 ], was also added to Consortium C. Interestingly, another Consortium H, created on the basis of the Rothia endophytica GMG9 strain, but with the addition of a strain with high siderophore production and antifungicidal activity (Enterobacter amnigenus GMG288 [ 13 ]), did not demonstrate an increase in available phosphates in the soil. Also, Consortia B, D, and E, which contained Azotobacter chroococcum GMG39 in combination with other phosphate-immobilizing bacteria, did not show any effect on the availability of phosphates in the soil and buckwheat yield.…”

“…Consortium C was based on the Rothia endophytica GMG9 strain, which de strated a high phosphate-immobilizing ability (248.3 µg/mL) in a laboratory exper [13]. An active nitrogen fixator, the strain Azotobacter chroococcum GMG39 [13], w so added to Consortium C. Interestingly, another Consortium H, created on the ba the Rothia endophytica GMG9 strain, but with the addition of a strain with high s phore production and antifungicidal activity (Enterobacter amnigenus GMG288 did not demonstrate an increase in available phosphates in the soil.…”