Microbial consortium of mineral solubilizing and nitrogen fixing bacteria for plant growth promotion of amaranth (Amaranthus hypochondrius L.)

Abstract

Globally, the chemical fertilizers use increases day by day for higher crop yield, which negatively affects the soil ecosystem. Over the past few decades, microbial bio-inoculants (single or multiple strains as consortium) have been recognized as potential plant growth promoters. Multiple microbial strains in a single formulation are a new growing trend for agricultural sustainability. In the present investigation, potential microbial consortium containing mineral solubilizing microbes (MSMs) and nitrogen fixing microbes were sorted out from the rhizospheric region of different crops growing in hilly regions of Himachal Pradesh and efficient bacterial strain were evaluated for growth and physiological parameters of Amaranthus crop. All 180 isolated bacterial strains were screened for phosphorus solubilization using insoluble source of phosphorus (rock phosphate, tricalcium phosphate, and apatite) and nitrogen fixation. The selected phosphorus solubilizers and nitrogen fixers were further screened for other plant growth-promoting attributes like solubilization of K and Zn; siderophores, ammonia, indole-3-acetic acid, 1-aminocyclopropane-1-carboxylic acid and hydrogen cyanide production. The efficient P-solubilizer and N-fixer bacterial strains were identified on the basis of 16S rRNA gene sequencing as Pseudomanas gessardi EU-LWNA-25 and Erwinia rhapontici EU-B1SP1. These bacterial strains were evaluated for plant growth promotion on Amaranthus crops under natural and controlled conditions. The selected stains increased the growth parameters (shoot/root length and biomass) and physiological (chlorophyll content, total sugar content, phenolics and flavonoids content) parameters of the treated plants compared to untreated control. These efficient MSMs and nitrogen fixing microbes as biofertilizer could be utilized for crops growing in hilly region for agricultural sustainability.