Mani Rajkumar¹, Viswanathan Subhadra Varshini¹, Ashok Suma Archana¹, Krishnan Sharmila^1,

An experiment was conducted to examine the efficiency of plant growth promoting rhizobacteria (PGPR) encapsulated in sodium alginate (SA) with either oak biochar (OK-BC) or sawdust biochar (SD-BC) at concentrations of 0. 2.5 and 5% on the growth of Zea mays. The PGPR strain SK1, isolated from the rhizosphere of Rhizophora mucronata, exhibited the potential to produce indole-3-acetic acid, siderophores, and solubilize phosphate. Based on 16S rDNA sequencing, strain SK1 was determined to be a member of the genus Bacillus. Characterization of the encapsulated beads revealed that the SA+SD-BC5%+SK1 formulation showed superior encapsulation efficiency, moisture retention, water absorption potential, and gradual release of SK1 cells compared to other treatments. Furthermore, the survivability of strain SK1 was remarkably increased in the SA+SD-BC5%+SK1 beads, maintaining viability after 80 days of storage even at room temperature. In pot experiments, Z. mays treated with SA+SD-BC5%+SK1 beads showed the greatest improvement in shoot length, root length, fresh weight, and dry weight relative to other treatments. Additionally, SA+SD-BC5%+SK1 beads improved the colonization of SK1 in the rhizosphere of Z. mays, which likely contributed to enhanced plant growth. In conclusion, the SA+SD-BC5%+SK1 formulation provided better survival and activity of PGPR compared to SA+SK1 beads alone, making it a promising and more effective carrier system for delivering beneficial microbes to the plant rhizosphere and thereby promoting plant growth.

PGPR, Sawdust biochar, Encapsulation, Zea mays, Indole-3-acetic acid, Encapsulation efficiency