Assessment of nitrogen-fixing endophytic and mineral solubilizing rhizospheric bacteria as multifunctional microbial consortium for growth promotion of wheat and wild wheat relative Aegilops kotschyi

Abstract

Microbes play crucial functions in maintaining the health and growth of the plants directly or indirectly by supplying nutrients. These microbes could be used as biofertilizers for the enhancement of soil health and growth of crops. In preset investigation, potential microbes from endophytic and rhizospheric region of Aegilops kotschyi growing in green slopes of Shivaliks, Himachal Pradesh were sorted out and screened for plant growth promoting attributes including phosphorus and potassium solubilization. The potential bacterial strains were identified through 16S rRNA gene sequencing and developed as microbial consortium for the plant growth of wheat and wild wheat relative Aegilops kotschyi. A total 125 isolates of bacteria were sorted out and among them 36 were found as P-solubilizers and 19 showed K-solubilization attribute and two highly potential bacterial strain were identified as Bacillus tropicus EU-ARP-44 (P-solubilizer; 270.5 ± 0.00 mg L^-1) and B. megaterium EU-ARK-23 (K-Solubilizer; 51.3 ± 1.7 mg mL^-1). The microbial consortium of Rahnella sp. strain EU-A3SNfb (N-fixer; MN294545), B. tropicus EU-ARP-44 (P-solubilizer) and B. megaterium EU-ARK-23 (K-solubilizer) evaluation in Aegilops kotschyi and wheat crop resulted in the enhancement of growth as well as physiological parameter including shoot/root length, fresh/dry weight and chlorophyll, carotenoid, total soluble sugar content, phenolic and flavonoid content as compared to un-inoculated control. Microbial consortium consisting of potential plant growth promoting (PGP) bacterial strains could be used as biofertilizer and bioinoculants in cereals crop growing in hilly region.

Keywords: Aegilops kotschyi; Agricultural sustainability; Bioinoculants; Endophytes; Plant growth promotion; Wheat.

Figure 1

Phylogenetic tree showing the relationship among nitrogen fixing, phosphorus and potassium solubilizing bacterial isolates, 16S rRNA gene sequences with reference sequences obtained through BLAST analysis. The trees were constructed using neighbor joining (NJ) with algorithm using MEGA 4 software (Tamura et al., 2007).

Figure 2

Effect of the bacterial consortium on the growth parameters of Aegilops kotschyi. Bacterial consortium: Rahnella sp. strain EU-A3SNfb, Bacillus tropicus EU-ARP-44, and B. megaterium EU-ARK-23; EU-A3SNfb: Rahnella sp. strain EU-A3SNfb (Nitrogen fixer); EU-ARP-44: Bacillus tropicus EU-ARP-44 (Phosphorus solubilizer); EU-ARK-23: B. megaterium EU-ARK-23 (Potassium solubilizer); DAP: Di-ammonium phosphate. [Common superscript code on mean values indicate the non-significant differences among derivatives as based on unpaired Student t-test at p < 0.05. On the other hand, different superscript indicates significant differences among lines].

Figure 3

Effect of the bacterial consortium on the growth parameters of wheat. Bacterial consortium: Rahnella sp. strain EU-A3SNfb, Bacillus tropicus EU-ARP-44, and B. megaterium EU-ARK-23; EU-A3SNfb: Rahnella sp. strain EU-A3SNfb (Nitrogen fixer); EU-ARP-44: Bacillus tropicus EU-ARP-44 (Phosphorus solubilizer); EU-ARK-23: B. megaterium EU-ARK-23 (Potassium solubilizer); DAP: Di-ammonium phosphate. [Common superscript code on mean values indicate the non-significant differences among derivatives as based on unpaired Student t-test at p < 0.05. On the other hand, different superscript indicates significant differences among lines].

Figure 4

a. Effect of bacterial consortium on chlorophyll content of Aegilops kotschyi. Bacterial consortium: Rahnella sp. strain EU-A3SNfb, Bacillus tropicus EU-ARP-44, and B. megaterium EU-ARK-23; EU-A3SNfb: Rahnella sp. strain EU-A3SNfb (Nitrogen fixer); EU-ARP-44: Bacillus tropicus EU-ARP-44 (Phosphorus solubilizer); EU-ARK-23: B. megaterium EU-ARK-23 (Potassium solubilizer); DAP: Di-ammonium phosphate. [Common superscript code on mean values indicate the non-significant differences among derivatives as based on unpaired Student t-test at p < 0.05. On the other hand, different superscript indicates significant differences among lines]. b. Effect of bacterial consortium on carotenoids content of Aegilops kotschyi. Bacterial consortium: Rahnella sp. strain EU-A3SNfb, Bacillus tropicus EU-ARP-44, and B. megaterium EU-ARK-23; EU-A3SNfb: Rahnella sp. strain EU-A3SNfb (Nitrogen fixer); EU-ARP-44: Bacillus tropicus EU-ARP-44 (Phosphorus solubilizer); EU-ARK-23: B. megaterium EU-ARK-23 (Potassium solubilizer); DAP: Di-ammonium phosphate. [Common superscript code on mean values indicate the non-significant differences among derivatives as based on unpaired Student t-test at p < 0.05. On the other hand, different superscript indicates significant differences among lines]. c. Effect of bacterial consortium on phenolic content of Aegilops kotschyi. Bacterial consortium: Rahnella sp. strain EU-A3SNfb, Bacillus tropicus EU-ARP-44, and B. megaterium EU-ARK-23; EU-A3SNfb: Rahnella sp. strain EU-A3SNfb (Nitrogen fixer); EU-ARP-44: Bacillus tropicus EU-ARP-44 (Phosphorus solubilizer); EU-ARK-23: B. megaterium EU-ARK-23 (Potassium solubilizer); DAP: Di-ammonium phosphate. [Common superscript code on mean values indicate the non-significant differences among derivatives as based on unpaired Student t-test at p < 0.05. On the other hand, different superscript indicates significant differences among lines]. d. Effect of bacterial consortium on flavonoid content of Aegilops kotschyi. Bacterial consortium: Rahnella sp. strain EU-A3SNfb, Bacillus tropicus EU-ARP-44, and B. megaterium EU-ARK-23; EU-A3SNfb: Rahnella sp. strain EU-A3SNfb (Nitrogen fixer); EU-ARP-44: Bacillus tropicus EU-ARP-44 (Phosphorus solubilizer); EU-ARK-23: B. megaterium EU-ARK-23 (Potassium solubilizer); DAP: Di-ammonium phosphate. [Common superscript code on mean values indicate the non-significant differences among derivatives as based on unpaired Student t-test at p < 0.05. On the other hand, different superscript indicates significant differences among lines]. e. Effect of bacterial consortium on soluble sugar content of Aegilops kotschyi. Bacterial consortium: Rahnella sp. strain EU-A3SNfb, Bacillus tropicus EU-ARP-44, and B. megaterium EU-ARK-23; EU-A3SNfb: Rahnella sp. strain EU-A3SNfb (Nitrogen fixer); EU-ARP-44: Bacillus tropicus EU-ARP-44 (Phosphorus solubilizer); EU-ARK-23: B. megaterium EU-ARK-23 (Potassium solubilizer); DAP: Di-ammonium phosphate. [Common superscript code on mean values indicate the non-significant differences among derivatives as based on unpaired Student t-test at p < 0.05. On the other hand, different superscript indicates significant differences among lines].

Figure 5

a. Effect of bacterial consortium on chlorophyll content of wheat. Bacterial consortium: Rahnella sp. strain EU-A3SNfb, Bacillus tropicus EU-ARP-44, and B. megaterium EU-ARK-23; EU-A3SNfb: Rahnella sp. strain EU-A3SNfb (Nitrogen fixer); EU-ARP-44: Bacillus tropicus EU-ARP-44 (Phosphorus solubilizer); EU-ARK-23: B. megaterium EU-ARK-23 (Potassium solubilizer); DAP: Di-ammonium phosphate. [Common superscript code on mean values indicate the non-significant differences among derivatives as based on unpaired Student t-test at p < 0.05. On the other hand, different superscript indicates significant differences among lines]. b. Effect of bacterial consortium on carotenoids content of wheat. Bacterial consortium: Rahnella sp. strain EU-A3SNfb, Bacillus tropicus EU-ARP-44, and B. megaterium EU-ARK-23; EU-A3SNfb: Rahnella sp. strain EU-A3SNfb (Nitrogen fixer); EU-ARP-44: Bacillus tropicus EU-ARP-44 (Phosphorus solubilizer); EU-ARK-23: B. megaterium EU-ARK-23 (Potassium solubilizer); DAP: Di-ammonium phosphate. [Common superscript code on mean values indicate the non-significant differences among derivatives as based on unpaired Student t-test at p < 0.05. On the other hand, different superscript indicates significant differences among lines]. c. Effect of bacterial consortium on phenolic content of wheat. Bacterial consortium: Rahnella sp. strain EU-A3SNfb, Bacillus tropicus EU-ARP-44, and B. megaterium EU-ARK-23; EU-A3SNfb: Rahnella sp. strain EU-A3SNfb (Nitrogen fixer); EU-ARP-44: Bacillus tropicus EU-ARP-44 (Phosphorus solubilizer); EU-ARK-23: B. megaterium EU-ARK-23 (Potassium solubilizer); DAP: Di-ammonium phosphate. [Common superscript code on mean values indicate the non-significant differences among derivatives as based on unpaired Student t-test at p < 0.05. On the other hand, different superscript indicates significant differences among lines]. d. Effect of bacterial consortium on flavonoid content of wheat. Bacterial consortium: Rahnella sp. strain EU-A3SNfb, Bacillus tropicus EU-ARP-44, and B. megaterium EU-ARK-23; EU-A3SNfb: Rahnella sp. strain EU-A3SNfb (Nitrogen fixer); EU-ARP-44: Bacillus tropicus EU-ARP-44 (Phosphorus solubilizer); EU-ARK-23: B. megaterium EU-ARK-23 (Potassium solubilizer); DAP: Di-ammonium phosphate. [Common superscript code on mean values indicate the non-significant differences among derivatives as based on unpaired Student t-test at p < 0.05. On the other hand, different superscript indicates significant differences among lines]. e. Effect of bacterial consortium on soluble sugar content of wheat. Bacterial consortium: Rahnella sp. strain EU-A3SNfb, Bacillus tropicus EU-ARP-44, and B. megaterium EU-ARK-23; EU-A3SNfb: Rahnella sp. strain EU-A3SNfb (Nitrogen fixer); EU-ARP-44: Bacillus tropicus EU-ARP-44 (Phosphorus solubilizer); EU-ARK-23: B. megaterium EU-ARK-23 (Potassium solubilizer); DAP: Di-ammonium phosphate. [Common superscript code on mean values indicate the non-significant differences among derivatives as based on unpaired Student t-test at p < 0.05. On the other hand, different superscript indicates significant differences among lines].