Characterization, Identification, and Biosafety Evaluation of Multifaceted Traits of Plant Growth-Promoting Endophytes for Ameliorating Productivity of Forage Sorghum.

Abstract

Endophytes are bacteria that inhabit host plants for most of their life cycle without causing harm. In the study, 15 endophytic bacteria were isolated from 30 forage Sorghum plants and assessed for various plant growth-promoting (PGP) traits, such as phosphate solubilization, 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase activity, ammonia production, siderophore production, gibberellic acid production, Indole-3-acetic acid (IAA) production, and zinc solubilization. One isolate, JJG_Zn, demonstrated multiple PGP activities and was identified as Enterobacter sp. through 16S rRNA sequencing. Considering the concept of 'One health,' a comprehensive biosafety analysis for any plant growth-promoting bacteria (PGP bacteria) is essential, thus, Enterobacter sp. (JJG_Zn), along with two other standard cultures, Burkholderia seminalis and Stenotrophomonas maltophilia, were evaluated for biosafety tests-including sheep blood agar assay, E.coli sensitivity assay, and pathogenicity tests on albino mice. The results indicated that all three PGP bacteria were potentially innocuous and compatible with each other. Furthermore, the field experiments were conducted at Punjab Agricultural University, Regional Research Station, Bathinda, and School of Organic Farming, IFS, Punjab Agricultural University, Ludhiana during Kharif 2022 employing a randomized complete block design (RCBD) with nine treatment combinations. The treatments included liquid bacterial inoculants (LBIs) of Stenotrophomonas maltophilia, Burkholderia seminalis, and Enterobacter sp. (JJG_Zn) applied in combination with 100% and 75% of the recommended dose of fertilizer (RDF), with each treatment replicated thrice. The treatment T₉ (75% RDF + dual inoculation with B. seminalis and S. maltophilia) resulted in the highest productivity, showing a 10.23% increase in pooled green fodder yield (GFY) compared to the control. The treatment T₈ (75% RDF + Enterobacter sp. (JJG_Zn)) showed a 5.14% increase in productivity over the control. Thus, liquid bacterial inoculants (LBIs) present a promising approach to enhance the productivity of forage Sorghum.